Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
851 PM EDT Thu Jul 16 2026
Day 1
Valid 01Z Fri Jul 17 2026 - 12Z Fri Jul 17 2026
...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
SOUTH-CENTRAL TEXAS...
01Z Update...
Previous update captured the evolution of convection well so only
some minor nudging of the risk area boundaries were needed. Texas
remained the prime candidate for catastrophic and life-threatening
flash flooding in the overnight hours given additional rainfall
on top of what has already overwhelmed some places. The channel of
moisture/instability fueling convection from Arizona/southwestern
New Mexico northward into parts of Wyoming and Montanan pretty well
established...changes were pretty small and largely made to fit
the latest radar trends.
Bann
16Z Update...
...Texas...
Catastrophic and life-threatening flash flooding continues in
the Texas Hill Country as the pain-stakingly slow MCV responsible
for the copious amounts of rainfall in recent days continues to
cause widespread excessive rainfall rates. Through the early
afternoon, the low-level jet will continue to supply low-level
moisture and shear into the Hill Country, helping to sustain the
current thunderstorm activity and their prolific rainfall rates
between 2-4"/hr in many cases. Meanwhile, 700mb flow is convergent
west of the Rio Grande and is aiding in providing some mid-level
ascent on the southern and eastern flanks of the MCV. WPC's
Metwatch issued an MPD (#740) that goes into more detail on the
evolving setup through early afternoon.
CAMs generally show the same pattern as recent days with thunderstorms
decreasing in areal coverage later this afternoon, only to re-
develop overnight as the low-level jet strengthens and diffluent
500-700mb flow supports upscale ascent. PWs tonight will continue
to be highly anomalous (>2.0") over the Hill Country on north and
west through north-central TX and the Edwards Plateau. The ongoing
stream of Gulf moisture will also accompany additional instability
as well, priming the atmosphere for another round of widespread
storms in areas hit this morning and even a little farther north
and west that include areas north and east of Del Rio towards the
Concho Valley. CAMs continue to disagree on exact placement, but
recent days of thunderstorm activity would suggest the more
southern and eastern envelope of solutions should be favored. New
12Z HREF and REFS shows moderate-to-high chances (50-70%) for >5"
of rainfall north and east of Del Rio, TX with a highly concerning
30-50% area for >8" through 12Z Friday when utilizing both ensemble
suites.
The High Risk was expanded a little farther N&W into areas north
and east of Del Rio where the remnant MCV will be tracking across
tonight, and the Moderate Risk encompasses more of the Concho
Valley. The region is facing tremendous ongoing impacts from
urban, stream, and river flooding and any additional rainfall is
going to exacerbate this ongoing catastrophic event. TX Hill
Country residents should continue to follow guidance from local
officials and maintain multiple ways to receive weather alerts
during this ongoing flood disaster.
...Elsewhere...
The Slight Risk in Arizona and southern Utah remains in good shape,
although there are locally some moderate chance probabilities
(40-60%) between the 12Z HREF and REFS for >3" of rainfall along
the southern periphery of the Mogollon Rim. The setup has more of a
look of a high-end Slight here, as areal extent of flash flooding
may not be high enough to warrant a Moderate Risk, but locally
significant flash flooding cannot be ruled out given the
sensitivities of the region and the potential 2"/hr rainfall rates.
The Marginal Risk was maintained from the Middle MS Valley on east
to the TN Valley. Signals in probabilistic guidance are not in
great agreement on exactly where to favor a Slight Risk at the
moment. That said, the Lower OH Valley and TN Valleys have 1-hr
FFGs that are <2" today and could be more favored for areas of localized
flash flooding this afternoon.
Mullinax
---Previous Discussion---
...Southwest into the Great Basin...
No significant changes were made to the risk areas out West for
this update. A prime monsoonal setup remains in place for southern
Arizona, where a Moderate Risk remains in place. PWs are expected
to climb above 2 inches, or exceeding 2 std dev normal, across
portions of southern Arizona. This moisture along with sufficient
instability and upper level support, will likely support terrain-
initiated thunderstorms. Subsequent rain-cooled outflows will drive
additional intense cells into the evening hours, pushing rainfall
rates up 2 inches/hr in some locations. A broader Slight Risk
encompasses much of Arizona, extending north into the slot canyons
of southern Utah and eastward into far western New Mexico.
...Mid Mississippi Valley into the Lower Ohio/Tennessee Valleys
and Southern Appalachians...
The Marginal Risk has been adjusted and expanded father east,
stretching from the Mid Mississippi Valley into portions of the
lower Ohio and Tennessee valleys, as well as the southern
Appalachians. A remnant mid-level shortwave moving into the region
will provide weak ascent. Southwesterly inflow into a downstream
boundary will support deepening moisture (PWs increasing to 1.75-2
inches). Both the HREF and REFS guidance are showing notable
probabilities for localized rainfall totals exceeding 2 inches.
Hourly rainfall rates along the boundary may support isolated flash
flood occurrences, particularly in complex terrain and urban
areas.
Pereira
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
851 PM EDT Thu Jul 16 2026
Day 2
Valid 12Z Fri Jul 17 2026 - 12Z Sat Jul 18 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF WEST
TEXAS, SOUTHERN NEW MEXICO, ARIZONA, AND THE SOUTHERN GREAT
BASIN...
20Z Update...
...Texas...
The MCV responsible for the catastrophic flooding in the Hill
Country will finally begin to make its way N&W on Friday. There
remains concern that the eastern and southern flanks will be close
enough to affected areas of central TX to further exacerbate flash
flooding, as well as along streams, creeks, and rivers. Moisture
content will remain quite anomalous for the time of year (1.8-2.0",
above the 90th climatological percentile) for much of central TX. A
revitalized low-level jet will also play a prominent role in
supplying both low-level moisture/theta-e advection, additional
MUCAPE, and an increase in low-level shear, giving storms
additional longevity into the late morning hours. CAMs show less
areal coverage compared to recent days, but given the strength of
the low-level jet (surpassing 30 kts) it will provide sufficient
inflow and some upslope enhancement into western portions of the
Hill Country and the Edwards Plateau through midday. The gradual
westward shift will mean more scattered to widespread showers and
storms throughout West Texas, and hourly rainfall rates around
2"/hr are possible even towards the Davis Mountains.
Most probabilistic guidance is at least in better agreement on an
axis of thunderstorms from the Rio Grande on north through the
Edwards Plateau and the Conch Valley Friday morning. Rainfall rates
between 2-3"/hr with peak maximum approaching 4"/hr remain
possible. In total, another 2-6" of rainfall is possible late
tonight and through Friday morning within that band of thunderstorm
activity, with locally higher amounts possible within the Slight
Risk from Del Rio on north to the Concho Valley. Additional
flash flooding is expected with significant flooding possible.
Should any storms ensue over areas hit in recent days over the Hill
Country, it could rejuvenate areas with lingering flood waters and
may result in renewed areas of dangerous flooding.
...Western Florida...
A cut-off 500mb low just west of Tampa Bay will reside within an
area where PWs between 2.0-2.2", which is hovering around the 90th
climatological percentile. MLCAPE over 1,000 J/kg and warm cloud
layers approaching 14,000' deep will provide developing
thunderstorms with a favorable environment to generate highly
efficient rainfall rates that could surpass 3"/hr in the most
intense cells. Given the greater Tampa/St. Petersburg area may also
have slightly more sensitive soils following today's storms, it is
possible localized flash flooding occurs within the more urbanized
areas of west-central FL. For these reasons, a Marginal Risk was
introduced this forecast update.
...Northern Arizona...
Newest 12Z HREF/12Z REFS guidance has shown an increased signal for
>3" and locally >5" rainfall totals in portions of the Mogollon Rim
for Friday. On the heels of an active Thursday, it is possible the
atmosphere is more over-worked and struggle to produce the too
excessive of rates. On the flip side, soils will be more sensitive
to additional thunderstorms. The setup supports a more "high-end"
Slight in the Mogollon Rim, suggesting more scattered instances of
flash flooding with the potential for localized significant flash
flooding, particularly near burn scars and dry washes.
Mullinax
---Previous Discussion---
...Southern New Mexico...
In southern New Mexico, storms are expected to develop along and
near the Sacramento Mountains by the afternoon and continue into
the evening before diminishing with the loss of diurnal heating.
Active wildfire burn scars in this region make it particularly
susceptible to rapid runoffs, supporting the continuation of the
Slight Risk.
...Western U.S./Great Basin...
Overall, only minor changes were made to the risk areas in the
West, as a persistent monsoonal pattern remains locked in place.
A robust moisture profile will sustain widespread convective
coverage from southern Arizona north-northeastward into the Great
Basin. Moisture anomalies will remain high, with standardized
anomalies of 2-3 extending all the way from the Southwest to the
northern Rockies.
This moisture, along with with sufficient instability will support
highly efficient rainfall rates. A broad Slight Risk was maintained
from southern Arizona to southern Utah, with complex terrain,
urbanized areas, and other vulnerable areas likely to a be a focus
for the greater runoff concerns across the region.
...Ohio/Tennessee Valleys into the Central and Southern
Appalachians....
A Marginal Risk covering much of the Ohio and Tennessee Valleys
into the central and southern Appalachians was maintained. Storms
developing across this region will be fueled by the same high-PW
airmass noted in the Day 1 period as it spread farther north and
east. These diurnally-driven storms are once again expected to
raise isolated runoff concerns.
...Northern Great Lakes...
A progressive upper trough digging southeast across central Canada,
will shift a notable jet max south into northern Minnesota. Strong
low level convergence along with favorable upper jet forcing will
support nocturnal storms from the Minnesota Arrowhead eastward into
Upper Michigan. Although fast storm motions will the heavy
accumulation and flash flooding threat, anomalous moisture
supporting heavy rates, along with some potential for brief
training, may raise isolated concerns.
Pereira
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
851 PM EDT Thu Jul 16 2026
Day 3
Valid 12Z Sat Jul 18 2026 - 12Z Sun Jul 19 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM WEST TEXAS AND
SOUTHERN NEW MEXICO TO SOUTHERN UTAH, AND OVER PORTIONS OF THE
NORTHERN MID-ATLANTIC...
20Z Update...
...Northern Mid-Atlantic...
A deepening area of low pressure in southern Ontario will work in
tandem with high pressure south of Bermuda to cause an acceleration
in southerly low-level winds over the Northern Mid-Atlantic
Saturday morning and into the afternoon hours. PWs will jump to
above 2.0" Saturday morning for areas such as northern MD,
southeast PA, all of NJ, and northward through NYC/Long Island and
along the southern New England coast. In the northern DelMarVa and
Delaware Valley, some guidance shows >2.2" PWs which tops the 97.5
climatological percentile. Strong low-level flow and rising dew
points will support pre-frontal thunderstorm activity Saturday
afternoon; some cases firing off the higher terrain to the west,
and in other cases through strong daytime heating and mid-70s dew
points simply breaking the capping inversion. Sufficient wind shear
will also be present to support potential mesocyclones, which
would further enhance excessive rainfall rates.
Surface winds out of the south to start the day would help direct
high theta-e air over the Chesapeake into these areas initially and
provide a more buoyant air-mass to support hourly rainfall rates
approaching 3"/hr. Additionally, various model guidance shows a
corridor of >2,000 J/kg MLCAPE moving from northeast MD into the
Delaware Valley Saturday afternoon. Given the region in the Slight
also sports a larger urbanized population, rainfall rates to this
caliber would be a recipe for flash flooding with such a high
concentration of hydrophobic surfaces. Parts of the Lehigh and
Susquehanna Valleys may be a little more resilient initially, but
additional thunderstorms look to come through Saturday evening as
the cold front approaches. In collaboration with PHI/CTP/LWX, a
Slight Risk was issued for portions of northeast MD, northern DE,
eastern PA, and much of NJ, while also including the greater
Philadelphia metro area. Should more guidance come into better
consensus on the positioning of heaviest rainfall over the I-95
corridor, the Slight Risk could see additional expansion in future
forecast cycles.
Mullinax
---Previous Discussion---
...Western U.S....
An expansive monsoonal convective pattern will continue, prompting
the inclusion of a Slight Risk stretching from West Texas and
southern New Mexico northwestward across Arizona and into southern
Utah. Overnight guidance indicated a notable uptick in low level
moisture transport into these region on Saturday. This surge will
act to revitalize the potential for additional rounds of high
rainfall rate convective cores capable of producing flash flooding.
Once again, the combination of anomalous moisture and instability
will support highly efficient rainfall rates within the stronger
storms. The threat of rapid runoff and flash flooding will be
elevated across the complex terrain, normally dry washes, and slot
canyons, as well as over highly sensitive soils and wildfire burn
scars.
...Ohio Valley/Central and Southern Appalachians to the Mid
Atlantic and Northeast...
The core of the high-PW airmass will continue to shift east, with
moisture pooling ahead of a strong cold front dropping south
across the Northeast. Strong synoptic forcing, driven by an
amplifying trough over the Northeast and favorable upper jet
dynamics, will support an axis of organized storms from the upper
Ohio Valley into the Northeast. Given the high PWs and strong
forcing, heavy rainfall rates producing at least localized runoff
concerns are expected. Given the uncertainty regarding where the
axis of heaviest rains will occur, maintained a Marginal Risk for
now. However, a targeted Slight Risk may be introduced in future
updates if confidence increases.
Pereira
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
851 PM EDT Thu Jul 16 2026
Day 4 and Day 5
Valid 12Z Sun Jul 19 2026 - 12Z Tue Jul 21 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE WEST ON DAYS 4 AND 5, THE VIRGINIA TIDEWATER ON DAY 4, AND
PORTIONS OF FLORIDA ON DAYS 4 AND 5...
2030Z Update...
Models still depict an active pattern between a risk of excessive
rainfall to portions of the western United States and parts of the
eastern/southeastern part of the country. Little run to run change
in the synoptic pattern meant little change in the QPF associated
with the monsoon in the western United States, Placement and timing
of QPF and any associated risk of excessive flooding in
Florida/adjacent part of the southeastern US states needed little
adjustment based on latest guidance.
Bann
Previous Discussion...
...Western U.S...
A traditional Monsoonal pattern will continue across the Western
CONUS with scattered to widespread bouts of heavy rainfall across
much of the Desert Southwest up through the Great Basin with an
northern inflection into portions of the Rockies. Ridging will
prevail across the west as we move through the weekend into early
next week with a solidified Monsoonal trough positioned over AZ
down through Mexico. Even at leads, there's a well- defined axis
of elevated instability coupling with PWAT anomalies between +2 and
+3 standard deviations positioned from the Great Basin to points
south with the strongest anomalies situated over NV and UT was
assessing both the ECENS and NAEFS anomaly forecast. QPF maxima
are currently situated within the Mogollon Rim and portions of
southern UT, both of which are the more susceptible areas given the
persistence of heavy rainfall leading in, plus the complex
topography and slot canyon allotment. This is really a seasonal
setup which could likely spur short term upgrades in spots as we
move closer to both the D4 and D5 time frame. Broad MRGL risks
exist for both days in similar locations outlining much of the
aforementioned area(s) above.
...Florida...
Models continue to depict heavy rainfall across the western coast
of FL on D4 (Sunday), spreading further east towards the northern
half of the state on D5 (Monday) thanks to developing mid-level
disturbance over the eastern Gulf. General model consensus is for a
development of heavier rains across the western FL coast with a
northern inflection into the Florida Big Bend thanks to increasing
low-level convergence on the eastern flank of a weak low center
progged off the coast. Ensemble QPF for both periods indicate
multiple inches of rain possible which could enhance further if
there is a greater likelihood of tropical cyclogenesis as noted via
the latest National Hurricane Center T.W.O for a disturbance of
interest (Disturbance 2) at 20% chance for development the next
7-days. This is a period to monitor for the prospects of this being
something more organized which models might not have a great grasp
of yet considering the lead time, and the slow maturation of any
organized low the next 5-7 days. For now, MRGL risks exist on both
D4 and D5 for the threat of heavy rainfall.
...Virginia Tidewater into Northeast North Carolina...
Slow-moving front will make headway through southeastern VA and
northeastern NC by Sunday with a deep moisture pooling anticipated
along and ahead of the front which will likely lead to areas of
heavy thunderstorms prior to fropa. Ensemble consensus lends
credence to a localized QPF maxima positioned somewhere around the
VA Tidewater through the northeastern corner of NC, coincident
with the progged frontal positioning around the time of Sunday
afternoon. PQPF for >1" is between 20-40% across the region which
at D4 is formidable enough to monitor closely. Considering some of
the more appreciable outputs via the global deterministic and bias
corrected ensemble, and in coordination with the local Wakefield,
VA WFO, opted to add a D4 MRGL risk for the threat, highlighting
that Tidewater area down into northeastern NC.
Kleebauer
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
851 PM EDT Thu Jul 16 2026
Day 4 and Day 5
Valid 12Z Sun Jul 19 2026 - 12Z Tue Jul 21 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE WEST ON DAYS 4 AND 5, THE VIRGINIA TIDEWATER ON DAY 4, AND
PORTIONS OF FLORIDA ON DAYS 4 AND 5...
2030Z Update...
Models still depict an active pattern between a risk of excessive
rainfall to portions of the western United States and parts of the
eastern/southeastern part of the country. Little run to run change
in the synoptic pattern meant little change in the QPF associated
with the monsoon in the western United States, Placement and timing
of QPF and any associated risk of excessive flooding in
Florida/adjacent part of the southeastern US states needed little
adjustment based on latest guidance.
Bann
Previous Discussion...
...Western U.S...
A traditional Monsoonal pattern will continue across the Western
CONUS with scattered to widespread bouts of heavy rainfall across
much of the Desert Southwest up through the Great Basin with an
northern inflection into portions of the Rockies. Ridging will
prevail across the west as we move through the weekend into early
next week with a solidified Monsoonal trough positioned over AZ
down through Mexico. Even at leads, there's a well- defined axis
of elevated instability coupling with PWAT anomalies between +2 and
+3 standard deviations positioned from the Great Basin to points
south with the strongest anomalies situated over NV and UT was
assessing both the ECENS and NAEFS anomaly forecast. QPF maxima
are currently situated within the Mogollon Rim and portions of
southern UT, both of which are the more susceptible areas given the
persistence of heavy rainfall leading in, plus the complex
topography and slot canyon allotment. This is really a seasonal
setup which could likely spur short term upgrades in spots as we
move closer to both the D4 and D5 time frame. Broad MRGL risks
exist for both days in similar locations outlining much of the
aforementioned area(s) above.
...Florida...
Models continue to depict heavy rainfall across the western coast
of FL on D4 (Sunday), spreading further east towards the northern
half of the state on D5 (Monday) thanks to developing mid-level
disturbance over the eastern Gulf. General model consensus is for a
development of heavier rains across the western FL coast with a
northern inflection into the Florida Big Bend thanks to increasing
low-level convergence on the eastern flank of a weak low center
progged off the coast. Ensemble QPF for both periods indicate
multiple inches of rain possible which could enhance further if
there is a greater likelihood of tropical cyclogenesis as noted via
the latest National Hurricane Center T.W.O for a disturbance of
interest (Disturbance 2) at 20% chance for development the next
7-days. This is a period to monitor for the prospects of this being
something more organized which models might not have a great grasp
of yet considering the lead time, and the slow maturation of any
organized low the next 5-7 days. For now, MRGL risks exist on both
D4 and D5 for the threat of heavy rainfall.
...Virginia Tidewater into Northeast North Carolina...
Slow-moving front will make headway through southeastern VA and
northeastern NC by Sunday with a deep moisture pooling anticipated
along and ahead of the front which will likely lead to areas of
heavy thunderstorms prior to fropa. Ensemble consensus lends
credence to a localized QPF maxima positioned somewhere around the
VA Tidewater through the northeastern corner of NC, coincident
with the progged frontal positioning around the time of Sunday
afternoon. PQPF for >1" is between 20-40% across the region which
at D4 is formidable enough to monitor closely. Considering some of
the more appreciable outputs via the global deterministic and bias
corrected ensemble, and in coordination with the local Wakefield,
VA WFO, opted to add a D4 MRGL risk for the threat, highlighting
that Tidewater area down into northeastern NC.
Kleebauer
