AWUS01 KWNH 292153
FFGMPD
TXZ000-300351-

Mesoscale Precipitation Discussion 1254
NWS Weather Prediction Center College Park MD
452 PM EST Sat Nov 29 2025

Areas affected...Southeast Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 292151Z - 300351Z

Summary...Thunderstorms near Houston TX are expected to grow
upscale and potentially backbuild/train with time. Hourly amounts
to 2.5" with local totals to 5" could lead to widely scattered
instances of flash flooding.

Discussion...Satellite and radar imagery indicate the formation of
showers and thunderstorms near and east of a baroclinic zone
oriented northwest-southeast across Southeast TX within a region
of 850 hPa confluence near I-10. ML/MU CAPE to the west and
southwest is 1000-2000 J/kg. Effective bulk shear is near 40 kts,
which has led to right movers near IAH itself. The atmosphere is
saturated, considering precipitable water values (1.25-1.5" per
GPS data) within a region of 5630 meter 1000-500 hPa thickness
values. Hourly rain amounts of are up to 0.5-1" in the past hour
near Stagecoach TX, as of the time of this discussion's writing.

The 18z HREF moreso than the 12z REFS indicates the continued
building of thunderstorms in this area, with some further increase
in convective coverage, which may show backbuilding, training
character with time. Instability could erode/retreat westward
with time depending upon the degree of convective coverage,
essentially stalling the front west of Houston. Cell mergers are
also possible as less organized convection moves more northeast
while more organized convection moves more to the east. Given the
parameters, hourly amounts to 2.5" with local amounts to 5" are
possible over the next several hours, with the magnitude most in
line with the 12z ARW and 20z HRRR guidance. There is a chance
late in the MPD period of convection trying to form across
northeast TX presently near and ahead of an advancing cold front
approaching the southeast TX convective area, which could lead to
more cell mergers at or beyond 04z. Since the 12z ARW and 18z
HREF are closer to the convective evolution thus far, used their
guidance for the defined MPD area. Widely scattered instances of
flash flooding are considered possible, particularly in the
Houston metropolitan area.

Roth

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-Vhatwq8jLS3mZorPAMnYdTnKTx4EfsxLABG-GVOUpKylJtFpPdI52knRINntAjzbM-p= HzQOyXL5ZWPQujCk3_4mvYw$ for graphic product...

ATTN...WFO...EWX...HGX...

ATTN...RFC...FWR...NWC...

LAT...LON 30579626 30439491 29959459 29489490 29339650=20
29869717=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

AWUS01 KWNH 300357
FFGMPD
LAZ000-TXZ000-301000-

Mesoscale Precipitation Discussion 1255
NWS Weather Prediction Center College Park MD
1056 PM EST Sat Nov 29 2025

Areas affected...Central and Upper Texas Coastal Plain...

Concerning...Heavy rainfall...Flash flooding possible

Valid 300400Z - 301000Z

SUMMARY...Slow moving, pre-frontal cells with rates of 2"/hr
eventually merge with south-southeastward pressing cold front
convection resulting in localized 2-4" totals in 1-3 hours.=20
Isolated flash flooding remains possible, especially near urban
centers.

DISCUSSION...GOES-E 3.9um SWIR highlights a few low level
boundaries that will remain the focus of scattered thunderstorm
activity through the overnight period. The main being the surging
cold front being reinforced by favorable upper-level orientations
to support steepening of theta-E gradient while increasing
northerly surface wind flow to over 20-25kts nearly counter to the
weaker but solid onshore flow. Currently active convection along
the leading edge of the front is slow moving from Burleson to Polk
county as the winds are not fully intersecting with the line, but
will likely be propagating southward in the next hour or so. The
other boundary is the return moisture plume off the western Gulf
(which arches similar to the Lower TX Gulf coast before angling
east- northeast just south of the aforementioned convection). Tds
in the upper 60s to near 70 can be traced best in CIRA LPW sfc-850
and 850-700mb layers covering much of the MPD area of concern
across the Central and Upper Texas Coastal Plain.

Onshore flow is also increasing to 15-20kts resulting in
frictional convergence near coast. Conditionally unstable airmass
with MLCAPEs of 1000-1250 J/kg remain weakly capped but there are
some signs in satellite imagery of some weak cu field near
Victoria, TX as well as an isolated weakening supercells
northeast of Galveston Bay. The merging of the boundaries is also
allowing a westward expansion of new development upstream into
Bastrop/Caldwell county vicinity.=20

Total deep moisture of 1.5" as noted in the CIRA LPW is loaded
below 700mb, but there is solid deep saturation. These isolated
cells driven by frictional convergence will be slow moving and
eventually capable of 1-2"/hr rates. Spotty 2-3" totals will
occur in 1-2hrs, but as they mature and expand the slower moving
cells along the cold front will have started increased forward
speed and with very high low level moisture flux convergence will
have the capability of 1-1.25"/15min rainfall totals as they
intersect/merge with the cells across the Plain.

00z HREF probabilities continue to suggest 3"/3hr totals in the
20-30% range (3"/6hr over 50%) which is fairly impressive given
the strength of the updraft due to instability is fairly limited.=20
While the overall coverage will continue to be limited, spots of
3-4" totals are probable through 09z. This places sufficient
overlap of FFG exceedance (as 1hr FFG is 2.5-3" and 3hr is 3-4")
for possible localized incident or two of flash/rapid inundation
flooding. This only further increases with intersection with
urban centers, such as Victoria, Houston and Beaumont.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6eBqZJFeXYwfdfjOanroH9GQeQtbydrQfNUR442JL4eOoRDBCnP5-W_eKdR2izXE3AJE= Wxq3reM5uV59a3QArZIE_ho$ for graphic product...

ATTN...WFO...CRP...EWX...HGX...LCH...

ATTN...RFC...FWR...NWC...

LAT...LON 30999472 30719393 30099362 29749380 29519420=20
29359466 28499607 27779725 27969777 28499795=20
29529752 29879714 30199681 30729602=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

AWUS01 KWNH 020035
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-020634-

Mesoscale Precipitation Discussion 1256
NWS Weather Prediction Center College Park MD
734 PM EST Mon Dec 01 2025

Areas affected...portions of the central Gulf Coast

Concerning...Heavy rainfall...Flash flooding possible

Valid 020034Z - 020634Z

Summary...A combination of cell training and backbuilding should
continue to lead to hourly rain amounts to 1.75" with local totals
to 4", which could cause flash flooding in urban areas.

Discussion...Instability across portions of the central Gulf Coast
continues to rise ahead of a negatively-tilted shortwave across
OK. Precipitable water values are ~1.6" per GPS data and MU CAPE
values of 500+ J/kg lie across the southeast tip of LA and
continue shifting north towards the MS/AL barrier islands. Radar
estimates from LIX/Hammond LA indicate that hourly amounts peaked
near 1.75" not far from the eastern suburbs of New Orleans
recently, with local totals above 2.5" so far. Occasional hourly
rain amounts to 1.5" have been seen in backbuilding convection in
southernmost AL. Effective bulk shear of 25-45 kts lurks across
the area which is helping to form a band within an area of 850 hPa
confluence.

The band is showing some signs of shifting northward across
southern AL and slightly eastward in southeast LA. Additional
activity south of the LA/MS coasts within a convergence zone which
extends from northwest Cuba towards the central Gulf Coast could
advect northward towards portions of this area in the next several
hours and cause additional issues. The guidance has not been
ideal in this region thus far -- too far north and too light --
though the 18z hi-res NAM appears to have the best idea, so used
it as a starting point for the MPD bounds, making some adjustments
based on radar reflectivity trends. The region has been dry, so
flash flood guidance values are high. Hourly amounts to 1.75" and
local totals to 4" appear possible where cells train and/or
backbuild, which would be most problematic in urban areas.

Roth

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6SdogcIUxTtroqQTUwxSALeN9Fo_uMvC5I4pW6eAAjX9DWw67VnyMfB31nkTA5_xaSPt= yY_XxORQJb-wb9BRCh179PU$ for graphic product...

ATTN...WFO...BMX...LIX...MOB...TAE...

ATTN...RFC...ALR...ORN...NWC...

LAT...LON 31928616 31298582 30558670 30248743 30078846=20
29938870 29778905 29439024 29689078 30768934=20
31778728=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

AWUS01 KWNH 080044
FFGMPD
FLZ000-080300-

Mesoscale Precipitation Discussion 1257
NWS Weather Prediction Center College Park MD
742 PM EST Sun Dec 07 2025

Areas affected...Portions of the Central Florida Peninsula

Concerning...Heavy rainfall...Flash flooding possible

Valid 080041Z - 080300Z

Summary...A combination of locally intense rainfall and cell
training should continue this evening which could cause flash
flooding in urban areas.

Discussion...Thunderstorms with isolated maximum rainfall rates
approaching 1.5 inches per hour have been moving on-shore and
tracking northeastward from near Tampa to Cape Canaveral early
this evening. These storms appear to be associated with a
mid-level vorticity maximum approaching from the eastern Gulf of
America along the axis of a 2+ inch precipitable water plume and
axis of boundary layer moisture flux convergence. Radar estimates
from TBW/Tampa Bay indicate that hourly amounts have peaked near
1.75 inches in parts of Pinellas and Pasco counties and that the
maximum rainfall totals were approaching 3.25 inches in the same
area. These amounts were embedded within a broader 1.5 to 2,5
inch stripe of rainfall extending towards the central portion of
the peninsula.

With additional showers and thunderstorms located off-shore...the
potential for flooding due to multiple rounds of heavy rainfall
exists. The 18Z HREF/RRFS showed the probability of 1 inch per
hour rates diminishing to less than 5 percent along the west-coast
by 08/03Z. Their placement has been a bit too far north with the
intense rates. Even so...the HREF captured the evolution in the
broadest sense and was used it as a starting point for the MPD.=20

Maximum Hourly amounts 1" to 1.75" and local totals to 3.5" appear
possible where cells train and/or back-build, which would be most
problematic in urban areas and regions of poor drainage as well as
along small streams.

Bann

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6pVmRublY1OVsAJkJg8O46F9ZFJcJq11wZG7H7yfyyETA4AMO-6DQLkDZoaZVaqobmxQ= aeSyDnVcKLlM3SGwH4kZuK0$ for graphic product...

ATTN...WFO...MLB...TBW...

ATTN...RFC...ALR...NWC...

LAT...LON 28538137 28538106 28328102 28008125 27678210=20
27488265 27958282 28338219 28488162=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

AWUS01 KWNH 081653
FFGMPD
ORZ000-WAZ000-090400-

Mesoscale Precipitation Discussion 1258
NWS Weather Prediction Center College Park MD
1152 AM EST Mon Dec 08 2025

Areas affected...Western Washington...Far Northwest Oregon...

Concerning...Heavy rainfall...Flash flooding possible

Valid 081700Z - 090400Z

SUMMARY...Very strong atmospheric river with persistent .25-.5"/hr
rates falling on increasingly saturated soils will result in high
run-off, swelling rivers and poor drainage/urban flooding but at
minimum further set the stage for expected additional rainfall
into the mid-week.

DISCUSSION...Regional RADAR mosaic is showing the leading
warm/moisture advection surge from the atmospheric river is
expanding across the Pacific Northwest and into the Washington
Cascades at this time. CIRA LPW animation depicts a long fetch
core to the atmospheric river with a long tap back to the tropics
near the Dateline; though the strength of the polar stream with
150-170kt fairly zonal upper-level jet has resulted in very strong
deep layer flow which has resulted in a fairly long/gradual
isentropic incline to deplete any potential of vertical
instability, the strength of moisture flux anomalies are pushing
the maximum climatological percentiles for this time of year. This
is generally confirmed by CIRA LPW percentiles in the 95-99th
range through all layers but most noted in the 700-500mb at this
time.

The total PWat values are at or above 1.25" and have come ashore
with the subtle but fast moving warm front denoted with wind shift
from south to southwest and increase to 40kts at surface, 50-60kts
near boundary layer and over 70kts at 700mb, this has lead to IVT
values very near 1000 kg/m/s analyzed just offshore while
remaining above 700 kg/m/s into the Cascades currently, but is
expected to rise as the effective warm sector moisture intersects
the terrain fairly orthogonally as well. As a result, broad
.25-.33"/hr rates have been seen near the coastal areas so far and
will expand into W WA over the next few hours. The nose of the
upper-jet remains north for a bit and height-falls on the western
side of the core will not start to dip southward until well after
00z as the cold front reaches the mouth of the Juan de Fuca Strait
around 00-01z.

The strong flux, upslope flow will allow for rates of .5"/hr
regularly through the mid to upper slopes of the Cascade Range as
the WAA has freezing heights above all but the highest peaks. As
such upper slopes will see 3-5" totals by 03z with foothills
likely to be 2-4" and lower valleys less than 2"...with isolated
totals to 6-7"+ along the core of the AR in the southern WA
Cascade Range. Coastal Ranges including the Olympics may see
4-6". Overall, FFG values are high enough even to encompass all
but those highest extreme values being greater than 3.5/3hrs and
over 5"/6hrs. However, NASA SPoRT LIS 0-40cm soil saturation
values are generally above 70-80% across which is generally a bit
above normal for the Coastal Range, but near 75-85th percentiles
for the Cascade Range; however, full saturation should occur
through the late afternoon, and as the main surge occurs toward
00z, much of the rainfall should convert to run-off. This should
swell the rivers fairly quickly with compounding issues resulting
in riverine flooding (please refer to discussion and graphical
products from NW River Forecast Center and National Water Center
for further details).

Given this is the first surge of a prolonged AR event, the
potential for flash flooding is likely limited to the highest
slopes/reaches of the watersheds or some localized urban flooding
due to poor drainage. With the saturation of the soils through
depth, there will be a slowly increasing potential for mudslides
especially near/downslope any recent burn scars.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!41Gpl_K0C4oZ8oksLbVkshXJ6rbtTPELhF_yqA-pb03G5RNZm1ZMxwDtMJ02CLLoM3h0= Gh03LT2xq3MSxojGryzr5JQ$ for graphic product...

ATTN...WFO...OTX...PDT...PQR...SEW...

ATTN...RFC...PTR...NWC...

LAT...LON 49112107 48812060 48292030 47312040 46882082=20
45752140 45492147 45512177 45902229 46102264=20
46062298 45822333 45732387 46362422 47182433=20
47832456 48222487 48462487 48292398 47902348=20
47362331 46992302 46942246 47252212 47702194=20
48252209 48572212 48962190 49092160=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

AWUS01 KWNH 092112
FFGMPD
ORZ000-WAZ000-100910-

Mesoscale Precipitation Discussion 1259
NWS Weather Prediction Center College Park MD
411 PM EST Tue Dec 09 2025

Areas affected...Northern Oregon and Western Washington

Concerning...Heavy rainfall...Flash flooding possible

Valid 092110Z - 100910Z

Summary...The ongoing atmospheric river event over the Pacific
Northwest will continue into tonight over portions of western
Oregon and Washington. The axis of heaviest rainfall is expected
to shift back north into Washington and also increase in
intensity, which will bring an increasing flood and landslide risk
to these areas.

Discussion...The expectation is that the atmospheric river
impacting northern OR will shift northward back into western WA
this evening. After a temporary drop in Integrated Water Vapor
Transport (IVT) today, values are forecast to increase again
towards 03z resulting in an uptick in rainfall coverage and
intensity into the overnight hours. With no forecast instability,
rainfall rates will be driven mostly by the magnitude of moisture
transport into the terrain. This will put a cap on the upper bound
of rainfall rates, although this will be compensated by IVT values
above the climatological 99th percentile and layered precipitable
water (PW) generally above the 95th percentile at all atmospheric
levels. This deep moisture and strong moisture transport will
support hourly rainfall in the 0.25"-0.40" range, potentially
approaching 0.50" in the highest mountain peaks. These rates
should increase in coverage after 03z (per the 12z HREF
probabilities), moving from northern OR into western WA overnight.
Additional rainfall through 09z Wednesday is generally expected to
be in the 1-3" range.

Under typical conditions, rainfall rates and totals of this
magnitude would not pose a significant hazard to this region.
However, the past 24 hours have already brought 4-10" of rain to
these locations, leading to saturated ground and elevated streams
and rivers. Although parts of WA saw a brief lull today allowing
for some recovery, hydrologic conditions remain sensitive.
Consequently, when heavier rain returns this evening into tonight,
additional flood impacts are expected.

The primary impacts are expected to be flooding of rivers and
streams, other low-lying flood-prone areas, and poor drainage and
urban areas. Given the saturated ground, the risk of landslides
and debris flows in areas of steep terrain will also increase
tonight as rainfall intensity ramps up.

Chenard

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!43p-OkfUop706I6cKLYBBIwzA6nB0hPZtCxkYgIrTsd-VTMoHaWWkfw9qP6uMmlQkjOt= HZdFGfUJBx9ZZGkLPPdfEFs$ for graphic product...

ATTN...WFO...OTX...PDT...PQR...SEW...

ATTN...RFC...PTR...NWC...

LAT...LON 47942123 47642074 46792112 46432130 45912145=20
45412151 45322145 44952164 44572184 44412215=20
44522255 44712277 45042250 45422224 45882270=20
45822308 45252331 44842354 44972399 45782413=20
46532407 47232417 47682412 47842384 47782333=20
47392322 47042294 46852251 47122208 47482197=20
47762182=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105)

AWUS01 KWNH 101628
FFGMPD
WAZ000-110300-

Mesoscale Precipitation Discussion 1260
NWS Weather Prediction Center College Park MD
1128 AM EST Wed Dec 10 2025

Areas affected...Olympic and Cascade Ranges of Western
Washington...

Concerning...Heavy rainfall

Valid 101630Z - 110300Z

SUMMARY...Core of next atmospheric river surge through evening.=20
Rates of .33-.75"/hr based on elevation likely to further compound
ongoing river flooding throughout the foothills of the Olympic and
Cascade Ranges. Mud/Landslide potential continues to increase
with amount of deep soil moisture.

DISCUSSION...Recent regional RADAR mosaic shows core of solid
stratiform rainfall is expanding across much of western
Washington. CIRA LPW shows solid sub-tropical moisture connection
tapping just northwest of Kaua'i only narrowing/concentrating
along and south of the stationary front 42N/142W to the Olympic
Range. RAP analysis and recent VWP network observations denote a
surge of increased moisture/warm advection south of the front is
directed orthogonally to the Olympic Range and further downstream
to the western Washington Cascades with 30-40kts of boundary layer
orographic ascent and Tds in the mid 50s. CIRA LPW also notes
that core of enhanced 850-700mb remains well displaced (east over
WA at this time) to the surface core indicative of the long,
gentle upslope of the AR moisture plume; so with limited unstable
air, orographic moisture flux convergence remains the primary
driver of intense rates, so stark rainshadows and much lower
rainfall totals/rates are expected in main, lower elevation
valleys.=20=20

CIRA LPW analysis, extrapolation shows core of enhanced moisture
below 700mb will continue to be directed toward the Juan de Fuca Strait/Northern Olympics into the Northern Washington Cascades
over the next 6-9hrs supporting rates of .25" in the valleys to up
to .75" in the highest terrain of the Cascades; and with the
strong warm sub-tropic air, all but the most extreme peaks will
continue to remain below the freezing levels. RAP/HRRR along with
LPW extrapolation suggest core of enhanced moisture and winds will
slowly reduce from supporting over 800 kg/m/s IVT values below 600
kg/m/s toward 00z with the front sagging south toward the mouth of
the Columbia river by 06z.=20=20

FFG values are static in the Pacific Northwest and are not likely
to be exceeded; however, NASA SPoRT shows 0-40cm saturation is
near 90%, so nearly all those rates will be fully run-off. Flash flooding/rapid inundation flooding is not expected except for the
highest reaches of watersheds/upper slope creeks, etc. but the
rainfall will definitely continue a steady rise/expansion of
ongoing river flooding across the area. Please refer to Northwest
River Forecast Center and National Water Center products for
details of these ongoing dangerous, life threatening conditions.=20

Additionally, deep layer saturation of the upper soils suggests
mud/landslides may become increasingly possible through this
evening, especially given affects of strong winds acting upon the
trees and therefore their roots. Remain aware of this potential
and refer to local emergency managers and USGS reports/products
regarding landslide concerns.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8L2D4ky7YUPIc_XTauE7f5mOBTS_tFcGMz7lVQIdQ_QXNey033P0XO5k-9kianVdLxxG= MzntNDwJCMC7cWkTFvSaRJ0$ for graphic product...

ATTN...WFO...OTX...PDT...SEW...

ATTN...RFC...PTR...NWC...

LAT...LON 49092147 48632099 48032072 47612090 46942137=20
46942189 47532210 47892184 48252199 48662228=20
49002260 48782323 47892312 47002346 47192395=20
47762440 48222461 48152365 48122326 49042328=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (1:2320/105)

AWUS01 KWNH 110408
FFGMPD
WAZ000-111530-

Mesoscale Precipitation Discussion 1261
NWS Weather Prediction Center College Park MD
1107 PM EST Wed Dec 10 2025

Areas affected...Western WA (including the Olympic Peninsula and
Cascades)

Concerning...Heavy rainfall...Flash flooding possible

Valid 110407Z - 111530Z

SUMMARY...Strong atmospheric river activity to continue overnight
across much of western WA with a focus for additional heavy rain
and locally significant areal flooding, including potential for
debris flows, landslides and localized flash flooding.

DISCUSSION...The latest GOES-W WV suite along with OSPO/CIRA ALPW
data sets show a well-defined and strong atmospheric river
continuing to advance inland across western WA, with an upstream
orthogonal orientation of the deep Pacific moisture axis/plume
relative to the Olympic Peninsula and the Cascades. Satellite and
radar data continue to show areas of heavy rain impacting these
areas with recent rainfall rates in the 0.25" to 0.40"/hour range.

Much of the deeper layer trans-Pacific moisture transport into the
region continues to be aided by the positioning of a strong
subtropical ridge near and offshore of CA, and an elongated axis
of mid-level troughing from the Gulf of AK southwestward to
30N/40N and 160W. Offshore experimental CIRA LVT data is showing
some gradual slackening of the low and mid-level moisture
transport around the top side of the ridge axis, and this may
allow for some of the more widespread heavier rainfall rates to
gradually subside a bit going through the overnight hours.

However, there will be the arrival of a new Pacific cold front
across the region as shortwave energy moves into British Columbia,
and this boundary should slowly push inland and become more
oriented west/east across southern WA Thursday morning. IVT
magnitudes along the front should remain elevated for the next 6
to 12 hours, but by early Thursday morning, these values are
forecast to drop down into the 600 to 800 kg/m/s range with the
overall slackening of the low to mid-level kinematic wind field
environment.

The 00Z HREF guidance does continue to support rainfall rates in
the Olympic Peninsula of around a 0.25"/hour, but with heavier
rates occasionally reaching a 0.50"+/hour in the central and
northern WA Cascades. Going through 15Z (7AM PST) on Thursday, an
additional 1 to 2 inches of rain is expected for the Olympic
Peninsula, but with an additional 2 to 4 inches in the central and
northern WA Cascades.

These additional rains will exacerbate ongoing areal flooding and
especially to the river basins which are locally seeing
significant impacts. Given the amount of rainfall that has
occurred over the last few days in the Cascades in particular
(with 12 to 15+ inches locally), the terrain is particularly
sensitive, with the additional rains favoring concerns for debris
flows, landslides and potential flash flooding around areas of
steep terrain.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!71Jepf9yev7hmkJDrRvmtLMcUq8j50D7FgYNO7kSskSH7SKK20EaAmLtVqgpFTJ6kFC0= SGJjw80lHp4zyyPnh7ywKDw$ for graphic product...

ATTN...WFO...OTX...PDT...PQR...SEW...

ATTN...RFC...PTR...NWC...

LAT...LON 49202170 49192044 48662002 47232051 46482165=20
46642366 47412470 48122487 48372444 48112360=20
48162268 48802244=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (1:2320/105)

AWUS01 KWNH 111452
FFGMPD
WAZ000-112048-

Mesoscale Precipitation Discussion 1262
NWS Weather Prediction Center College Park MD
951 AM EST Thu Dec 11 2025

Areas affected...portions of western Washington State

Concerning...Heavy rainfall...Flash flooding possible

Valid 111448Z - 112048Z

Summary...Ongoing moderate to heavy rainfall will continue to
foster excessive runoff and flood/flash flood issues through at
least 20Z/noon Pacific time.

Discussion...A persistent atmospheric river continues to spread
areas of moderate to heavy rainfall across the discussion area.=20
Recent rain rates ranging from 0.15-0.5 inch/hr have been noted -
especially in terrain-favored upslope areas of the Cascades. The
rainfall was tied to strong 700mb flow perpendicular to the
Cascades and 1 inch PW values - supporting abundant orographic
ascent and precipitation. Unfortunately, these rain rates were
continuing to impact inundated areas that have experienced 6-10
inches of rain over the past 72 hours, with widespread,
significant riverine flooding being reported as a result.

Rainfall could continue for another 4-6 hours across the region.=20
Eventually, models depict a weakening of 700mb flow over the
Cascades as mid/upper ridging builds northward into the region.=20
This may reduce acute flash flood potential, though riverine
issues will likely continue for some time.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-ImXPjaEKxXDP2MXZn5DlOqZ-jEGbNw9fZaPqxDHzK7LZF4ZyYLNeT4WwF3zvzlNd8sy= HiRwBZt23t60q5z8yF4V1K8$ for graphic product...

ATTN...WFO...OTX...PDT...PQR...SEW...

ATTN...RFC...PTR...NWC...

LAT...LON 48592119 48222044 47562035 46522081 46302172=20
46582328 47552397 48042403 48322289 48502243=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.

--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (1:2320/105)