AWUS01 KWNH 252009
FFGMPD
NVZ000-CAZ000-260208-

Mesoscale Precipitation Discussion 1001
NWS Weather Prediction Center College Park MD
408 PM EDT Mon Aug 25 2025

Areas affected...Sierra Nevada...Southern CA

Concerning...Heavy rainfall...Flash flooding likely

Valid 252008Z - 260208Z

SUMMARY...Scattered thunderstorms with heavy rainfall rates are
likely through this afternoon across portions of the Peninsular
Range of southern CA, and also into the central and southern
Sierra Nevada. Scattered areas of flash flooding are likely, and
this may include a threat for burn scar flash flooding and debris
flow activity.

DISCUSSION...The early afternoon GOES-W Day Cloud Phase RGB
satellite imagery shows convective initiation underway across the
higher terrain of the Peninsular Range of southern CA and also up
across the central and southern Sierra Nevada. Daytime heating and
the build of surface-based instability along and adjacent the
terrain is fostering favorable differential heating boundary and terrain-enhanced circulations/ascent for convection which should
generally expand in coverage over the next several hours.

Monsoonal moisture remains quite prevalent and especially in the
850/500 mb layer based on the latest CIRA-ALPW data. This is
helping to drive PW anomalies again that are 1.5 to 2.5 standard
deviations above normal. This moisture along with the increasing
instability and orographic footprint of the convection should
yield rainfall rates this afternoon reaching as high as 1.5 to 2
inches/hour, with some of the heaviest rates probably focused over
the Peninsular Range of southern CA where moisture here is a tad
deeper (noting the 500/300 mb layer) relative to areas farther
north. Also, there is some very moist low-level southeast flow off
of the northern Gulf of California playing a role here in driving
greater nearby instability.

The convection today should again follow the diurnal heating
cycle, and by late today, some spotty rainfall amounts of 2 to 4
inches will be possible. This is supported locally by the latest
experimental WoFS guidance, and especially over the Peninsular
Range. Given the sensitivities with localized burn scar areas and
the rugged terrain in general, scattered areas of flash flooding
are likely. Some debris flow activity will be possible where any
burn scar flash flooding occurs.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4ndsX6KA9fEXjpy0wdelhQQz5tqrzimNfEaoVjf97bEyQm3PQrit_tXPEeD8qz5kZXqZ= mrIcsIrA4pRFv1MUuipHEN0$ for graphic product...

ATTN...WFO...HNX...LOX...PSR...REV...SGX...STO...VEF...

ATTN...RFC...RSA...NWC...

LAT...LON 39441960 38271829 36641772 35181763 34091633=20
32511581 32361649 33041699 33451730 34271799=20
34491839 34811881 34981884 35391887 36041883=20
36871906 37631967 38742031 39392040=20

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AWUS01 KWNH 252037
FFGMPD
AZZ000-UTZ000-NVZ000-260235-

Mesoscale Precipitation Discussion 1002
NWS Weather Prediction Center College Park MD
436 PM EDT Mon Aug 25 2025

Areas affected...Southern NV...Southern UT...Central and Northern
AZ

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

Valid 252035Z - 260235Z

SUMMARY...Monsoonal showers and thunderstorms will continue to
develop and locally expand in coverage over the next several
hours. Mainly isolated areas of flash flooding will be possible.

DISCUSSION...The early afternoon GOES-W visible satellite imagery
shows monsoonal shower and thunderstorm activity initiating and
expanding in coverage across northern AZ into southern NV and
southern UT. MLCAPE values have increased to as much as 1000+ J/kg
and the PW environment remains quite moist with values running 1
to 2 standard deviations above normal.

An additional uptick in instability is expected over the next few
hours which should work in tandem with orographics to drive an
increase in the coverage of showers and thunderstorms. The
convection will be capable of producing high rainfall rates of up
to 1.5 inches/hour.

The latest RAP guidance shows an increasing amount of mid-level
southeast flow over central to northwest AZ and by later today
around the western flank of the mid-level subtropical ridge/high
centered along the AZ/NM border. Some effective bulk shear values
may reach as high as 30 to 40+ kts which may support some
organized convective structures in time that will further support
high rainfall rates with enhanced updrafts, but also localized
areas of convective sustenance/persistence near areas of higher
terrain and including the Mogollon Rim.

Some localized 2 to 3+ inch rainfall amounts will be possible, and
this will favor a threat for at least isolated areas of flash
flooding going through the afternoon and early evening hours. Slot
canyon and burn scar flash flooding impacts will be associated
with this threat.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_6UrYYzzMV4wXzh-OCvNO05LJPNUBUksnlOX0bw1zxCRsg4AfJSKHNEnulSQNpjlDCM5= EiiYIjgxBLjGSM_dBiDMrOw$ for graphic product...

ATTN...WFO...FGZ...LKN...SLC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 39131105 38541061 36681097 35611074 34901014=20
34351027 34131095 34411197 35601347 36101538=20
36681620 38001616 38711532 38911365 38781251=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 252146
FFGMPD
AZZ000-CAZ000-260145-

Mesoscale Precipitation Discussion 1003
NWS Weather Prediction Center College Park MD
545 PM EDT Mon Aug 25 2025

Areas affected...Southern CA...Southwest to South-Central AZ

Concerning...Heavy rainfall...Flash flooding likely

Valid 252145Z - 260145Z

SUMMARY...Locally very heavy monsoon-driven showers and
thunderstorms are expected going through the remainder of the
afternoon across southern CA into southwest and south-central AZ.
Scattered areas of flash flooding are likely, some of which may be
locally significant.

DISCUSSION...The mid-afternoon GOES-W VIS/IR satellite imagery
shows deepening and cooling convective tops across southeast CA
and into adjacent areas of southern AZ where radar is confirming
multiple concentrated bands of very heavy shower and thunderstorm
activity.

Mesoscale boundary forcings/interactions along with terrain
influence and proximity of a very moist and unstable airmass is
expected to drive corridors of additional convection with high
rainfall rates going into the evening hours. MLCAPE values of 1500
to 2500 J/kg are noted with recent CIN erosion helping to yield
the recent uptick and organization of convection across southern
CA and southern AZ. This includes the Peninsular Range and the
adjacent deserts off to the east and south.

Given the level of focused instability over the region with PWs
reaching nearly 2.5 standard deviations above normal (with support
from the very warm nearby Gulf of California), some rainfall rates
may reach 2 to 2.5 inches/hour, with some spotty storm totals over
the next few hours of 3 to 4+ inches. Recent WoFS guidance output
suggests this potential, which will be aided by some localized
cell-merger activity.

Additional areas of flash flooding will be likely, some of which
may be locally significant near areas of higher terrain and also
for the dry wash/arroyo locations near and away from active areas
of heavy shower and thunderstorm activity.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7vkAaj75rcrt-PIafMfdv1fVW3ZEAJXG763nWXhF9O2-b5Z22oJsCgvTPWRZV_AGO3EW= JGgmSXtpxO1OjwL-sJcN_vA$ for graphic product...

ATTN...WFO...PSR...SGX...TWC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 34681677 34481604 33611488 33431359 33201277=20
33111094 32761015 31791014 31241072 31481240=20
32001378 32321480 32411608 32861673 33841716=20
34521716=20

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AWUS01 KWNH 260111
FFGMPD
AZZ000-NVZ000-CAZ000-260600-

Mesoscale Precipitation Discussion 1004
NWS Weather Prediction Center College Park MD
910 PM EDT Mon Aug 25 2025

Areas affected...Southern and Eastern CA...Western and Southern AZ

Concerning...Heavy rainfall...Flash flooding likely

Valid 260110Z - 260600Z

SUMMARY...Additional areas of flash flooding will be likely going
through the evening hours across portions of southern and eastern
CA through western and central AZ.

DISCUSSION...The late-day GOES-W IR satellite imagery shows an
extensive convective cloud canopy over areas of southern and
eastern CA into western and central AZ. Very heavy showers and
thunderstorms continue to locally percolate across the region in
response to localized outflow boundary collisions and some
orographically focused ascent.

Diurnally driven instability continues to be gradually consumed
via the process of convective overturning, but MLCAPE values
remain locally over 1000 J/kg across some of the open desert areas
of eastern CA and also through central AZ with much of this area
so far escaping much of the convective activity.

Recent runs of the experimental WoFS suggest some additional focus
for mesoscale-driven shower and thunderstorm activity across
central AZ in particular which may be aided by close proximity of
some mid-level vort energy lifting northwestward out of the far
northern Gulf of California.

There is also a belt of relatively stronger effective bulk shear
lifting up across southern and central AZ around the western side
of the subtropical ridge off to the east. This shear and the
lingering instability with generally moist deep layer southeast
monsoonal flow will likely support convection lingering well into
the evening.

Rainfall rates will continue to be capable of reaching up to 1.5
inches/hour with the stronger convective cores, with some
additional spotty totals of 2 to 3 inches possible. The 90th
percentile 6-hour QPF from 00Z WoFS supports this over parts of
central and southwest AZ.

This will continue to promote isolated to scattered areas of flash
flooding through this evening before the convection gradually
weakens. Any burn scar locations and the normally dry washes will
continue to be most susceptible to impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9--6CKs_-_lYZCLU7KMZAHifHRWpc2GOFL6JGPBpgoiQTrScsha74K5421HW9LeKLvGB= wTnDG-GyDAvrDDq_Ybxelho$ for graphic product...

ATTN...WFO...FGZ...HNX...LOX...PSR...SGX...TWC...VEF...

ATTN...RFC...RSA...STR...NWC...

LAT...LON 36671703 35421529 35601313 35541191 35241105=20
34731033 33951015 33091063 32361180 32151283=20
32281408 32571515 33061606 33641703 34921774=20
36511781=20

=3D =3D =3D
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AWUS01 KWNH 260159
FFGMPD
TXZ000-OKZ000-COZ000-NMZ000-260757-

Mesoscale Precipitation Discussion 1005
NWS Weather Prediction Center College Park MD
957 PM EDT Mon Aug 25 2025

Areas affected...Central and Southern CO...Central and Northern
NM...TX Panhandle

Concerning...Heavy rainfall...Flash flooding likely

Valid 260157Z - 260757Z

SUMMARY...Showers and thunderstorms will continue to develop and
concentrate across portions of central and southern CO into
northern and central NM. This will especially include the higher
terrain of the Sangre De Cristo Range and adjacent areas of the
High Plains. Scattered to numerous areas of flash flooding are
expected tonight.

DISCUSSION...The early evening GOES-E IR satellite imagery shows
an expansive area of very cold-topped convection impacting areas
of southern CO and especially central to northeast NM as heavy
showers and thunderstorms interact with the higher terrain of the
Sangre De Cristo Range along with favorable upslope flow.

A corridor of MLCAPE values reaching 500 to 1000+ J/kg continue to
be focused over north-central and northeast NM, with a separate
axis of instability also still seen over parts of southeast CO.
The environment remains very moist with PWs near 2 standard
deviations above normal. This coupled with highly favorable
orographic forcing/ascent and subtle mid-level vort energy
dropping southeast across the central Rockies should favor
additional concentrated areas of heavy showers and thunderstorms
over the next several hours.

The recent satellite and radar trends along with the last several
runs of the experimental WoFS guidance would suggest northeast NM
will be the primary focus for the heaviest rainfall amounts. This
is where more favorable easterly low-level upslope flow into the
terrain along with interaction with a stationary front will be
noted. Greater instability in this area too should tend favor this
area seeing the heaviest rainfall rates which is further supported
by some of the very cold convective cloud tops currently over the
region.

Rainfall rates with the stronger storms may be capable of reaching
2 inches/hour, and with the persistent upslope flow and frontal
convergence, some additional rainfall totals of 3 to 5 inches will
be possible. By later in the night, some of these heavier rains
over northeast NM should begin to edge out into the TX Panhandle
area which is strongly supported by the latest WoFS guidance.

Scattered to numerous areas of flash flooding are generally
expected, and especially over northeast NM where the heaviest
totals should focus. Some locally significant impacts cannot be
ruled out which may locally include sensitive burn scar locations.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!57uYAAIHBw_igN2z_cY9bvwL-kp0N83T1IorXzGeoUX7BSi49Mlolm9b_jQcNijREk9W= nSyuLqmd9TPFr_wfGMwHztk$ for graphic product...

ATTN...WFO...ABQ...AMA...BOU...GJT...LUB...PUB...

ATTN...RFC...FWR...KRF...STR...TUA...NWC...

LAT...LON 39300478 38880387 38250352 36830313 36120235=20
35730073 35120039 34490124 34360351 34060485=20
34120636 34430722 35260750 36450676 37490671=20
38540640 39150583=20

=3D =3D =3D
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