731
FOUS30 KWBC 200052
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
852 PM EDT WED AUG 19 2026
DAY 1
VALID 01Z THU AUG 20 2026 - 12Z THU AUG 20 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF INDIANA AND OHIO...
A VERY SLOW-MOVING FRONT ACROSS INDIANA AND OHIO IS PROVIDING
PLENTIFUL FORCING FOR SLOW, AND IN SOME CASES STATIONARY, MOVING-
THUNDERSTORMS ACROSS CENTRAL INDIANA AND OHIO THIS EVENING. WHILE
THE LINE OF STORMS IS GENERALLY THIN, ONLY ABOUT 30-50 MILES ACROSS
FROM NORTH TO SOUTH, THE VERY SLOW MOVEMENT OF THE STORMS IS STILL
RESULTING IN MULTIPLE INCHES OF RAIN PER HOUR RATES THAT ARE
OCCURRING ACROSS THESE STATES. MOST OF THE STORMS ARE AT LEAST
TRYING TO INCH SOUTHWARD, BUT AS THEY APPROACH I-70, SEVERAL URBAN
AREAS SUCH AS INDIANAPOLIS, DAYTON, AND COLUMBUS, OH ARE IN THE
PATH OF SOME OF THEM, ESPECIALLY INDIANAPOLIS. LIKE ALL URBAN
CENTERS, THESE AREAS ARE ESPECIALLY PRONE TO FLASH FLOODING.
FURTHER, THIS PORTION OF INDIANA AND OHIO HAVE BEEN HIT REPEATEDLY
WITH ROUND AFTER ROUND OF HEAVY RAIN OVER THE PAST SEVERAL DAYS TO
A WEEK, SO IN ADDITION TO ONGOING LINGERING FLOODING, THE SOILS IN
THIS AREA ARE FULLY SATURATED, SO ALL NEW RAINFALL FROM THE ONGOING
STORMS WILL CONTRIBUTE TO RENEWED RUNOFF, AND SUBSEQUENTLY RIVER,
STREAM, AND CREEK RISES. THE MODERATE RISK WAS EXPANDED WEST A
COUNTY OR SO INTO VERMILION COUNTY IN FAR EASTERN ILLINOIS, AS THIS
SEEMS TO BE ABOUT WHERE THE BACK EDGE OF THE SLOW-MOVING LINE OF
STORMS IS STOPPING. THE CLUSTER OVER WESTERN ILLINOIS IS QUITE
FAST-MOVING, AND IS LIKELY TO START ABSORBING AND ENDING THE
PERSISTENT RAINFALL OVER ILLINOIS OVER THE NEXT FEW HOURS.
THE SLIGHT RISK AREA WAS EXPANDED EAST TO INCLUDE THE PITTSBURGH
METRO AREA. THE ONGOING STORMS OVER OHIO SHOULD BEGIN TO MOVE MORE
QUICKLY TO THE EAST, BUT GIVEN THE RESERVOIR OF MOISTURE FOR THOSE
STORMS TO WORK WITH, AND DESPITE A WORSENING ENVIRONMENT, SOME
PERIOD OF MODERATE RAINFALL IS LIKELY TO IMPACT WESTERN
PENNSYLVANIA IN THE PREDAWN HOURS. BETWEEN URBAN EFFECTS AND
TERRAIN, HERE TOO FLASH FLOODING COULD BE MORE WIDELY SCATTERED
WHEN THE HEAVIER RAINS MOVE THROUGH LATER TONIGHT.
NO CHANGES WERE MADE OUT WEST WITH THE SOMEWHAT MOVING STORMS
TOWARDS THE SOUTHWEST HAVE GENERALLY KEPT FLASH FLOODING IMPACTS
ISOLATED, ONCE IMPACTS DUE TO BURN SCARS ARE REMOVED.
FINALLY, ALONG THE GULF COAST, THE MARGINAL IN NORTHEAST FLORIDA
WAS MOVED INTO THE PANHANDLE AND SOUTHERN ALABAMA DUE TO ONGOING
STEADY MODERATE TO HEAVY RAIN, AS WELL AS A FEW SLOW-MOVING STORMS.
HERE THE FFGS ARE VERY HIGH, AS IS THE BASE LEVEL FOR THIS AREA, SO
DESPITE THE HEAVY RAINFALL RATES WITH THE STRONGEST STORMS, ONLY
ISOLATED FLASH FLOODING IS POSSIBLE HERE.
WEGMAN
DAY 2
VALID 12Z THU AUG 20 2026 - 12Z FRI AUG 21 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MID ATLANTIC...
..2030Z UPDATE
THE MAIN UPDATE FOR THIS FORECAST CYCLE WAS TO MODESTLY EXPAND AND
THEN EXTEND THE INHERITED SLIGHT RISK OVER THE MID-ATLANTIC
NORTHWARD TO INCLUDE MORE OF THE I-95 CORRIDOR FROM PHILADELPHIA TO
THE NEW YORK CITY METRO. AS OUTLINED BELOW, A LINE OF
THUNDERSTORMS IS EXPECTED TO DEVELOP ALONG THE EASTWARD MOVING COLD
FRONT AS IT REACHES THE I-95 CORRIDOR. THE NOW AVAILABLE CAMS SHOW
CONSIDERABLE RAINFALL POTENTIAL (LOCAL AMOUNTS OF 3-6") FROM THE
VIRGINIA TIDEWATER NORTH-NORTHEASTWARD THROUGH DELMARVA AND INTO
FAR SOUTHEASTERN PA, MOST OF NJ, AND THE NYC METRO. THIS IS BACKED
UP BY MODERATE (40-70%) HREF/RRFS PROBABILITIES OF RAIN TOTALS
GREATER THAN 3", AND LOW END (20-30%) PROBABILITIES OF GREATER THAN
5". THERE REMAINS SOME UNCERTAINTY WITH THE TIMING/PROGRESSION OF
THE COLD FRONT AND WHEN STORMS FORM ALONG/AHEAD OF IT RELATIVE TO
THE I-95 CORRIDOR BEFORE MOVING EASTWARD, BUT AGAIN THE LATEST CAM
GUIDANCE DID SHOW NOTABLE AGREEMENT AT LEAST FOR THE NORTHERN
EXTENT OF THE RISK. THE RISK REMAINS JUST TO THE EAST FURTHER SOUTH
FROM BALTIMORE TO DC EXCEPT FOR SOME OF THE MORE EASTERN
SUBURBS/EXURBS AND TOWARDS ANNAPOLIS/CHESAPEAKE BAY. IN THE
SOUTHWEST, THE FORECAST REMAINS UNCHANGED FOR THE INHERITED
MARGINAL RISK COVERING ADDITIONAL MONSOON ACTIVITY.
PUTNAM
..PREVIOUS DISCUSSION
..MID ATLANTIC
SHORTWAVE OVER THE OHIO VALLEY WILL CONTINUE ITS PROGRESSION TO
EAST, THEN NORTHEAST AS IT MIGRATES INTO THE CENTRAL AND NORTHERN
MID ATLANTIC BY THURSDAY AFTERNOON. AT THE SURFACE, A COLD FRONT
WILL REMAIN STEADFAST ON ITS ADVANCEMENT THROUGH THE PIEDMONT AND
THE EASTERN SECTIONS OF PA BY LATE-THURSDAY MORNING LEADING TO A
FAVORABLE SCENARIO FOR A LINE OF THUNDERSTORMS TO DEVELOP ALONG AND
EAST OF THE FRONT ITSELF. INCREASED DYNAMICAL FORCING AND
FAVORABLE DIFFLUENT FLOW WITHIN THE RER OF A 130KT JET OVER THE
NORTHEAST U.S. WILL LEAD TO A BLOSSOMING OF AFTERNOON CONVECTION
WITHIN PROXIMITY OF THE FRONT ITSELF. LATEST CAMS ARE QUITE
AGGRESSIVE ON THEIR INTERPRETATION OF BOTH THE MAGNITUDE AND
COVERAGE OF THE HEAVY CONVECTIVE SIGNALS, ESPECIALLY FOR AREAS
EXTENDING FROM NORTHERN NJ DOWN THROUGH EASTERN PA, THE DELMARVA,
AND THE VA TIDEWATER. THUNDERSTORM INITIATION WILL BE VERY CLOSE TO
THE METRO AREAS OF DC-BALT-PHILADELPHIA WITH THE MAJORITY OF CAMS
DEVELOPING CELLS ALMOST OVERHEAD BEFORE ADVANCING STEADILY
EASTWARD, AWAY FROM THE I-95 CORRIDOR. THE THREAT WILL BE CLOSE FOR
THE URBAN CENTERS WITH THE PHILADELPHIA METROPOLITAN AREA THE
CLOSEST FOR MORE SUBSTANTIAL IMPACTS FROM CONVECTION WHEN YOU
CORRELATE WITH THE MEAN QPF OUTPUT IN THE REGION.
PWATS BETWEEN 2-2.3" COUPLED WITH A STRONG THETA_E RIDGE IN PLACE
AHEAD OF THE FRONT PROMOTES A FORMIDABLE ENVIRONMENT CAPABLE FOR
PRODUCING SIGNIFICANT RAINFALL RATES IN ANY CONVECTIVE CORE THAT
MATERIALIZES. ANALYSIS OF MULTIPLE SOUNDINGS FROM BOTH THE GLOBAL
AND HI-RES SUITE AT 00Z INDICATED A TEXTBOOK SIGNAL FOR HEAVY
RAINFALL WITH A TALL, SKINNY CAPE SIGNATURE WITH MOISTURE LAYERS
PRESENT FROM SURFACE TO THE TROPOPAUSE. TYPICALLY THESE TYPES OF
ENVIRONMENTS FAVOR, AT LEAST SCATTERED FLASH FLOOD PROSPECTS IN
AREAS WHERE THUNDERSTORMS REACH THEIR MATURE PHASES, WHICH SEEMS TO
ALIGN WITH AREAS ALONG AND EAST OF I-95. THE MOST NOTABLE HEAVY
RAIN DEPICTIONS FAVOR NJ/DE/VA TIDEWATER FOR THE TIME BEING AS THE
FRONTAL PROGRESSION TIMES WELL WITH THE LATE-AFTERNOON PERIOD, A
TIME FRAME WHEN DIURNAL INSTABILITY HAS REACHED ITS MAXIMUM. THE
SIGNAL IS PRETTY CLOSE TO THE NYC METRO, BUT THE HEAVIEST MAY LIE
JUST SOUTH OF THE METRO AREA, SO IT WILL BEAR WATCHING THE TRENDS
OVER THE NEXT 24 HRS TO SEE IF A HIGHER RISK IS NECESSARY FOR NEW
YORK TO WESTERN LI. FOR NOW, A MRGL RISK ENCOMPASSES THIS
PARTICULAR ZONE WITH AREAS JUST SOUTH WITHIN THE ADDED SLGT RISK.
THE DC/BALT METRO AREA IS CURRENTLY IN A MRGL WITH THE NEW SLGT
JUST TO THE EAST OVER PRINCE GEORGES AND ANNE ARUNDEL COUNTIES.
AREAS EAST OF THE CHESAPEAKE ARE FIRMLY INTO THE SLGT RISK, AS IT
STANDS AS THE SIGNAL IS THE MOST ROBUST IN THAT PARTICULAR
CORRIDOR.
..SOUTHWEST U.S. INTO THE SOUTHERN ROCKIES
RELATIVELY TEXTBOOK MONSOONAL PATTERN ACROSS THE WEST WILL LEAD TO
SCATTERED THUNDERSTORM DEVELOPMENT ACROSS MUCH OF THE DESERT
SOUTHWEST EXTENDING NORTH INTO PARTS OF THE GREAT BASIN AND THROUGH
THE SOUTHERN ROCKIES. AS OF NOW, THE SIGNAL IS MAINLY SEASONAL WITH
REGARDS TO THE PWAT ANOMALIES AND GENERAL EXPECTATION AS THE MOST
NOTABLE AREAS WILL LIKELY BE IN THOSE TERRAIN FOCUSED ZONES ACROSS
AZ (MOGOLLON RIM), NM (SANGRE DE CRISTOS AND SACRAMENTO MTNS.), AND
UT (ZION NATIONAL PARK). LOW PROBS FOR >1" ON THE LATEST
ECENS/GEFS SUITES AND 01Z NBM ALLOW FOR A STANDARD MRGL RISK
ISSUANCE FOR THE AREA AS THE SETUP IS GENUINELY FAVORED FOR PULSE
CONVECTION AND SLOW CELL MOTIONS TIED TO THE TERRAIN AS A BROAD
597DM RIDGE CENTERS OVER THE FOUR CORNERS AND MAKES LITTLE
PROGRESSION IN THE D2 WINDOW. NO CHANGES WERE NECESSARY TO THE
PREVIOUS FORECAST GIVEN THE CONSISTENCY WITHIN GUIDANCE OVER THE
LAST SERIES OF MODEL RUNS. MOST FAVORABLE AREAS OF IMPACT WILL
INCLUDE THE MORE FLASHY STREAMS AND ARROYOS ACROSS THE SOUTHWEST,
AS WELL AS THE SLOT CANYON AREAS OF SOUTHWEST UT AND THE BURN SCARS
ACROSS EACH OF NM AND AZ.
KLEEBAUER
DAY 3
VALID 12Z FRI AUG 21 2026 - 12Z SAT AUG 22 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
VIRGINIA AND THE CAROLINAS...
..2030Z UPDATE
ONLY ONE MAIN AREAL ADJUSTMENT WAS MADE TO THE INHERITED SLIGHT
RISK BASED ON THE LATEST GUIDANCE, WITH THE RISK AREA EXTENDED A
BIT FURTHER TO THE NORTHEAST OVER THE VIRGINIA TIDEWATER REGION AND
TO THE MARYLAND EASTERN SHORE. QPF AMOUNTS HAVE TRENDED UP THROUGH
THIS REGION AND THIS AREA WILL ALSO LIKELY HAVE SEEN AN INITIAL
ROUND OF HEAVY RAIN DURING THE DAY 2 PERIOD. STORM COVERAGE OVERALL
WILL SHIFT SOUTHWARD COMPARED TO THURSDAY WITH DEVELOPMENT FOCUSED
ALONG CONSOLIDATING FRONTAL BOUNDARIES THROUGH THE SOUTHERN MID-
ATLANTIC AND INTO THE CAROLINAS. THE LATEST 12Z DETERMINISTIC
GUIDANCE CONTINUES TO DEPICT LOCALLY HEAVY RAINFALL TOTALS IN THE
3-5" RANGE. THE AI GUIDANCE (NOTABLY THE ECMWF AIFS) IS LESS
BULLISH ON THE NORTHWARD EXTENT OF THE HEAVY RAINFALL, LEADING TO A
BIT MORE UNCERTAINTY INTO VIRGINIA AND THE MARYLAND EASTERN SHORE.
HOWEVER, AS NOTED, THE OTHER DETERMINISTIC GUIDANCE HAS ACTUALLY
COME UP IN AMOUNTS THROUGH THIS REGION.
AS DURING THE DAY 2 PERIOD, MONSOONAL ACTIVITY IS EXPECTED TO
CONTINUE THROUGHOUT MUCH OF THE SOUTHWEST WITH AT LEAST AN ISOLATED
RISK FOR FLASH FLOODING. THE INHERITED MARGINAL RISK WAS MOSTLY
LEFT UNCHANGED EXCEPT FOR A SMALL EXPANSION OVER PORTIONS OF
EASTERN NEW MEXICO TO COVER MORE BURN SCAR REGIONS WHERE THE LATEST
GUIDANCE DOES DEPICT SOME STORM POTENTIAL.
PUTNAM
..PREVIOUS DISCUSSION
..VIRGINIA TO CAROLINAS
COLD FRONT WILL SLOWLY ADVANCE SOUTH INTO THE CAROLINAS DURING THE
END OF THE D2 INTO D3 TIME FRAME WITH AN EVENTUAL TRANSITION TO A
QUASI-STATIONARY FRONT AS IT REACHES THE LATITUDE OF NORTH GA INTO
THE PIEDMONT OF SC. MOISTURE POOLING ALONG THE FRONT WITH CONTINUED
FORCING DRIVEN BY ANOTHER SHORTWAVE ADVANCING THROUGH THE
TENNESSEE VALLEY WILL LEAD TO ANOTHER ROUND OF HEAVY CONVECTION IN-
OF THE SOUTHERN MID ATLANTIC WITH THE PRIMARY AXIS LIKELY TO OCCUR
FROM THE SOUTHERN DELMARVA THROUGH THE VA TIDEWATER INTO THE
CAROLINA'S. ENVIRONMENT ACROSS THE REGION OUTLINED WILL REMAIN VERY
BUOYANT WITH PWATS BETWEEN 2-2.3" FOR THE ENTIRE AREA ALONG AND
SOUTH OF THE FRONT. MODELS ARE CONSISTENT WITH THEIR SIGNATURE OF
1-2" OF RAINFALL ON AN AREAL AVERAGE BASIS WITH SOME OF THE
DETERMINISTIC OUTPUTS APPROACHING UPWARDS OF 3-5" WHERE STORM
MATERIALIZE AND SETTLE AS THE STEERING PATTERN WEAKENS
SIGNIFICANTLY AS WE STEP INTO THE D3. RAINFALL RATES BETWEEN
2-3"/HR WITH INTRA-HOUR RATES UPWARDS OF 4"/HR ARE FORECAST ACROSS
THE AFOREMENTIONED AREA, PLENTY AGGRESSIVE ENOUGH TO CAUSE AT LEAST
SCATTERED FLASH FLOOD PROSPECTS, ESPECIALLY IN MORE URBANIZED
ZONES ALONG I-95 AND POINTS EAST. THE MOST NOTABLE LOCATIONS IN THE
GUIDANCE ARE OVER THE COLUMBIA, SC AREA UP THROUGH FLORENCE INTO
SOUTHEASTERN NC. WITH THE SIGNAL MAINTAINING CONSISTENT IN THE
HEAVY QPF PLACEMENT AND WITH A FAVORABLE ENVIRONMENT FOR LOCALLY
ENHANCED RAINFALL, THE SLGT RISK WAS GENERALLY MAINTAINED FROM THE
PREVIOUS FORECAST.
..SOUTHWEST
MONSOONAL ACTIVITY WILL CONTINUE FOR ANOTHER DAY AS THE SOUTHWEST
CONUS LIES UNDERNEATH A BROAD RIDGE CENTERED OVER THE FOUR CORNERS
WITH MULTIPLE MID-LEVEL VORTICITY MAXIMA PIVOTING UNDER THE RIDGE
AXIS. SEASONAL TO SLIGHTLY ELEVATED PWATS WILL EXTEND THROUGHOUT
THE SOUTHWEST, EVEN REACHING A BIT FURTHER NORTH INTO THE GREAT
BASIN BY FRIDAY LEADING TO SOME LOCALLY HEAVY RAINFALL EVEN MAKING
ITS PRESENCE INTO PORTIONS OF NV AND CENTRAL UT WHILE ALSO
IMPACTING THOSE SAME AREAS THAT SAW ACTIVITY THE PRIOR PERIOD.
LOCAL TOTALS OF 1-2" ARE FORECAST, BUT AREAL QPF AVERAGE IS PRETTY
MUCH BETWEEN 0.25-0.5" WHICH IS TYPICAL FOR THESE TYPES OF SETUPS.
A BROAD MRGL REMAINS IN EFFECT FOR MUCH OF THE DESERT SOUTHWEST UP
INTO THE GREAT BASIN, EXTENDING EAST INTO THE SOUTHERN ROCKIES
LOCATED OVER SOUTHWESTERN CO INTO NM.
KLEEBAUER
DAY 4 AND DAY 5
VALID 12Z SAT AUG 22 2026 - 12Z MON AUG 24 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE EAST COAST, SOUTHWEST AND INTERMOUNTAIN WEST...
..2030Z UPDATE
ONLY SMALL CHANGES WERE NEEDED TO THE PREVIOUS FORECASTS FOR THIS
WEEKEND. THE MARGINAL ON SATURDAY WAS EXPANDED NORTH UP THE NEW
ENGLAND COAST. WHILE THERE IS UNCERTAINTY WITH BOTH THE TIMING OF
THE RAIN (WHETHER IT WILL BE FULLY OFF THE COAST BY SATURDAY) AND
HOW HEAVY IT WILL BE (INSTABILITY WILL BE A LIMITING FACTOR), URBAN
AREAS FURTHER EAST, INCLUDING PROVIDENCE, RI AND BOSTON, MA BOTH
HAVE A HIGHER CHANCE OF SEEING AT LEAST STEADIER RAINFALL, AS NOTED
BY THE HIGHER QPF. GIVEN THE SENSITIVE NATURE OF THOSE URBAN AREAS
REGARDING ONSET OF FLASH FLOODING, AND POTENTIAL FOR AT LEAST SOME
INSTABILITY TO SUPPORT PERIODS OF HEAVIER RAINFALL, THE MARGINAL
RISK WAS EXTENDED.
A SLIGHT RISK MAY NEED TO BE CONSIDERED FOR COASTAL AREAS OF NORTH
CAROLINA AS WELL WITH FUTURE UPDATES IF DELAYS THAT FAIL TO MOVE
THE FRONT ALONG IN THAT AREA PERSIST.
MONSOON RAINS CONTINUE IN THE AFTERNOONS OF BOTH WEEKEND DAYS
ACROSS MUCH OF THE WEST. A BIT OF TRIMMING WAS DONE ON THE WESTERN
SIDE, TO INCLUDE WESTERN ARIZONA AND SOUTHERN NEVADA DUE TO LACK OF
APPRECIABLE RAINFALL FORECAST IN THOSE AREAS ON SATURDAY.
TRANSIENT MCSS MAY IMPACT PORTIONS OF THE PLAINS AND LOWER TO MID
MISSISSIPPI VALLEY THIS WEEKEND, WHICH MAY REQUIRE AT LEAST A
MARGINAL RISK TO BE ISSUED WITH FUTURE UPDATES, BUT LARGE
UNCERTAINTY ABOUT WHERE THEY WILL BE PRECLUDED THAT ISSUANCE AT
THIS TIME.
WEGMAN
..PREVIOUS DISCUSSION
..EAST COAST
THE MID TO UPPER TROUGH DEEPENS FURTHER OVER THE EASTERN U.S. ON
SATURDAY, BUT THE NORTHERN STREAM ENERGY CURRENTLY APPEARS
SEPARATED FROM THE DEEPER MOISTURE PLUME FURTHER SOUTH AND EAST.
WHILE ADEQUATE INSTABILITY AND UPPER LEVEL FORCING WILL SUPPORT
SCATTERED THUNDERSTORM DEVELOPMENT ACROSS PORTIONS OF MI, OH AND
NY, PWS APPEAR INSUFFICIENT TO SUPPORT FLASH FLOODING, PARTICULARLY
GIVEN EXPECTED QUICK CELL MOTIONS. THUS THE MARGINAL RISK WAS
REMOVED ACROSS THIS REGION.
THE BETTER THREAT FOR HEAVY RAINFALL WILL REMAIN FOCUSED FROM THE
COASTAL CAROLINAS INTO THE MID-ATLANTIC, WHERE A LINGERING
STATIONARY FRONT INTERACTS WITH THE BEST OVERLAP OF INSTABILITY
AND HIGH PW VALUES. FORECAST CONFIDENCE IN A CONTINUED FLASH FLOOD
THREAT IS HIGHEST ALONG THE COASTAL CAROLINAS, WHERE STRONGER
INSTABILITY IS MORE LIKELY, AND ANTECEDENT RAINFALL IN PRIOR DAYS
MAY LOWER FFG. CONFIDENCE IS LOWER ACROSS THE COASTAL MID-
ATLANTIC, AS THE AXIS OF INSTABILITY AND MOISTURE COULD GET SHUNTED
OFFSHORE. HOWEVER, THE MARGINAL RISK WAS MAINTAINED HERE AS A FEW
MODELS STILL INDICATE LOCALLY HEAVY RAIN POTENTIAL AND THE CSU
MACHINE LEARNING ERO GUIDANCE HIGHLIGHTS A SMALL SLIGHT RISK AREA.
NO MARGINAL RISK IS DELINEATED ON DAY 5 (SUNDAY) GIVEN SPATIAL
UNCERTAINTY AND THE HIGHER PROBABILITY THAT THE DIGGING TROUGH
DOES NOT TAP INTO THE BETTER MOISTURE POOL. HOWEVER, IF THE UPPER
TROUGH DIGS MORE AND TAKES ON A NEGATIVE TILT, DEEPER MOISTURE
COULD GET DRAWN BACK INTO THE SYSTEM, RESULTING IN SOME FLASH FLOOD
RISK OVER NEW ENGLAND. THUS WE WILL CONTINUE TO MONITOR TRENDS.
..SOUTHWEST AND INTERMOUNTAIN WEST
BROAD MARGINAL RISKS REMAIN IN PLACE ACROSS PORTIONS OF THE WEST
THIS WEEKEND. PLENTIFUL MONSOONAL MOISTURE AND DAYTIME INSTABILITY
WILL PROMOTE LOCALIZED FLASH FLOODING BOTH DAYS. BECAUSE CONVECTIVE
DEVELOPMENT WILL REMAIN LARGELY TIED TO TERRAIN DRIVEN FORCING,
OVERALL COVERAGE IS EXPECTED TO STAY BELOW SLIGHT RISK THRESHOLDS.
ON SATURDAY THE HIGHEST PW ANOMALIES ARE FORECAST TO BE CENTERED
OVER UT, WY, ID AND SOUTHERN MT, WHERE VALUES ARE EXPECTED TO
EXCEED THE CLIMATOLOGICAL 90TH PERCENTILE. SUFFICIENT INSTABILITY
SHOULD BE IN PLACE, ALONG WITH SOME LARGE SCALE FORCING ON THE
PERIPHERY OF THE UPPER RIDGE...TO RESULT IN SCATTERED CONVECTION
AND LOCALIZED FLASH FLOOD POTENTIAL. THE MARGINAL RISK WAS
EXPANDED NORTHWARD TO INCLUDE THESE AREAS.
CHENARD
DAY 1 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/94EPOINTS.TXT
DAY 2 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/98EPOINTS.TXT
DAY 3 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/99EPOINTS.TXT
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