389
FOUS30 KWBC 192013
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
413 PM EDT FRI JUN 19 2026
DAY 1
VALID 16Z FRI JUN 19 2026 - 12Z SAT JUN 20 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN EFFECT FOR
PORTIONS OF THE CENTRAL GULF COAST REGION...
..16Z UPDATE
NO MAJOR CHANGES WERE NEEDED FOR THE RISK AREAS WITH THIS UPDATE.
MUCH OF THE EXPECTED RAINFALL IS ONGOING IN THE DEFINED RISK AREAS
ACROSS TEXAS, AND FOR THE MDT RISK REGION, MORE WIDESPREAD
SCATTERED CONVECTION IS EXPECTED TO DEVELOP OVER THE NEXT FEW HOURS
WITH DAYTIME HEATING. THE CONVECTION APPEARS UNLIKELY TO BECOME
VERY ORGANIZED, INSTEAD FAVORING PULSE THUNDERSTORMS OR SMALL
CLUSTERS. CELL MERGERS APPEAR TO BE THE BIGGEST THREAT WHEN IT
COMES TO LOCALIZED RENEWED FLASH FLOODING THIS AFTERNOON IN THE
MODERATE RISK AREA ACROSS SOUTHERN ALABAMA AND MISSISSIPPI.
ELSEWHERE, A HIGHER-END SLIGHT HAS BEEN ISSUED FOR NORTHERN
LOUISIANA INTO NORTHEAST TEXAS FOR THE ONGOING VERY SLOW-MOVING
STORMS THAT ARE APPROACHING TEXARKANA. THESE STORMS ARE EXPECTED TO
CONTINUE BUILDING EASTWARD INTO THE AFTERNOON, FOLLOWED BY A BREAK
IN THE AREA FOR MUCH OF THE OVERNIGHT. ADDITIONAL CONVECTION COULD
DEVELOP IN THE EARLY MORNING HOURS.
THE SLIGHT OVER GEORGIA WAS EXPANDED TO NEAR THE COAST FOR THE
ONGOING TRAINING STORMS IN THAT AREA, WHICH COULD PERSIST INTO THE
AFTERNOON.
FINALLY, THE MARGINAL RISK ACROSS THE EASTERN CAROLINAS WAS DROPPED
WITH THIS UPDATE AS THE RAIN ONGOING THERE PUSHES OFFSHORE AND MUCH
DRIER AIR REPLACES THEM, ENDING EVEN A MARGINAL FLOODING THREAT
THERE.
WEGMAN
..PREVIOUS DISCUSSION
..CENTRAL GULF COAST STATES
LINGERING FLOOD IMPACTS FOLLOWING THE DELUGE OVER THE LAST 24
HOURS WILL BE EXACERBATED BY ADDITIONAL ROUNDS OF SLOW-MOVING
CONVECTION TODAY FROM CENTRAL MS AND EASTERN LA TO THE FL PANHANDLE
AND FAR SOUTHWEST GA. LOW-TO-MID LEVEL CONVERGENCE WILL EXTEND IN
A WEST-EAST ORIENTATION JUST TO THE NORTH OF THE GULF COAST AND
REMAIN A FOCUS FOR BROKEN AREAS OF SHOWERS AND THUNDERSTORMS
THROUGHOUT THE DAY. THESE STORMS WILL TAP INTO PWS ABOVE 2" AND
REMAIN RELATIVELY SLOW-MOVING WITH WESTERLY CONVERGENT 850MB FLOW
LESS THAN 15 KTS, LEADING TO HOURLY RATES OF 2-3"/HR. ACTIVITY WILL
LIKELY BE ONGOING ACROSS THE REGION AT 12Z AND PULSE THROUGHOUT
THE DAY AND INTO THE OVERNIGHT PERIOD. 00Z HREF PROBABILITIES FOR
AT LEAST 3" PER 6-HRS START THE DAY 1 PERIOD AS HIGH AS 60% ACROSS
SOUTHERN AL AND THE FL PANHANDLE BEFORE BECOMING MORE SCATTERED IN
NATURE AND LOWERING TO AROUND 30% FOR THE OVERNIGHT PERIOD. THE
PRIMARY FACTOR FOR MAINTAINING THE MDT RISK IS THE FACT THAT THESE
STORMS ARE LIKELY TO OVERLAP WITH AN AREA THAT RECENTLY RECEIVED
WIDESPREAD 4-8" RAINFALL TOTALS (LOCALLY OVER 12") AND SOILS ARE
EASILY OVERCOME WHEN RAINFALL RATES EXCEED 2"/HR. THIS WILL LEAD TO
ADDITIONAL SCATTERED FLASH FLOOD CONCERNS ON TOP OF ONGOING FLOOD
IMPACTS AND RECOVERY EFFORTS.
..SOUTHERN PLAINS TO THE UPPER TEXAS COAST
SCATTERED FLASH FLOODING IS ALSO A CONCERN FROM SOUTHERN OK INTO
MUCH OF CENTRAL AND EASTERN TX TODAY AS THUNDERSTORM ACTIVITY
BEGINS EARLY THIS MORNING AND GRADUALLY MEANDERS EAST WITH TIME
THROUGH TONIGHT. VAST AMOUNTS OF UNCERTAINTY EXIST WITH THE
MESOSCALE DETAILS SURROUNDING THE EXCESSIVE RAINFALL FORECAST IN
THIS AREA, PARTICULARLY FOR BEING A DAY 1 FORECAST, BUT PWS
NEAR/SLIGHTLY ABOVE 2" AND WIDESPREAD DEW POINTS INTO THE UPPER 70S
AND LOW 80S POINT TO AN ENVIRONMENT RIPE FOR INTENSE RAINFALL
RATES. AS CONVECTION DEVELOPS EARLY THIS MORNING THE EXPECTATION IS
FOR AN MCV OR MULTIPLE MCVS TO SPAWN AHEAD OF AN APPROACHING WEAK
SHORTWAVE AND WITHIN A BUILDING RIDGE OVER THE SOUTH-CENTRAL U.S..
THIS WEAK STEERING PATTERN WILL LEAD TO CONDITIONS WHERE MCV
LOCATION AND OUTFLOW BOUNDARIES COULD DRIVE THE CONVECTIVE MODE.
EVEN IF THUNDERSTORMS REMAIN MOSTLY PROGRESSIVE AFTER COLD POOLS
DEVELOP, INTENSE RAINFALL RATES OF 2-3" ARE POSSIBLE THROUGHOUT THE
SOUTHERN PLAINS INTO EASTERN TX AND THE ARKLATEX. ONE AREA OF
FOCUS TO MONITOR INTO THE OVERNIGHT PERIOD INTO SATURDAY MORNING
WILL BE ACROSS EASTERN TX INTO CENTRAL LA WHERE A FRONTAL BOUNDARY
IS FORECAST TO DRAPE AND POTENTIAL INTERACT WITH A WEAK SURFACE
LOW OR REMNANT MCV. SEVERAL CAMS INDICATE MORE WIDESPREAD
THUNDERSTORM ACTIVITY AROUND 12Z SAT. HERE OR JUST TO THE SOUTH
ACROSS SOUTHEAST TX AS THE NOCTURNAL LOW-LEVEL FLOW INCREASES
TOWARDS THE FRONTAL BOUNDARY. 00Z HREF NEIGHBORHOOD PROBS FOR AT
LEAST 3" PER 6-HRS ARE GENERALLY AROUND 30% HERE, BUT REFS PROBS
ARE MUCH HIGHER (60%) AND FARTHER SOUTH ALONG THE UPPER TX
COASTLINE. THUS, A LARGE SLGT RISK IS IN EFFECT FOR THIS REGION TO
HIGHLIGHT THE WIDELY SCATTERED/UNCERTAIN NATURE OF THUNDERSTORMS,
BUT WHILE ALSO LIKELY CONTAINING INTENSE RAINFALL RATES CAPABLE OF
FLASH FLOOD IMPACTS.
SNELL
DAY 2
VALID 12Z SAT JUN 20 2026 - 12Z SUN JUN 21 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL PLAINS AND MISSOURI VALLEY...
..2030Z UPDATE
FEW CHANGES WERE NEEDED FOR THE SATURDAY/DAY 2 PERIOD. EXPECTED
RAINFALL OVER THE CENTRAL PLAINS MODERATE RISK AREA REMAINS VERY
SIMILAR TO THE PREVIOUS FORECAST. DESPITE HEAVY RAINS IN THE AREA
IN RECENT WEEKS, SOILS IN THE AREA HAVE HAVE SOME TIME TO DRY OUT,
WHICH SHOULD WORK TO MITIGATE SOME OF THE FLOODING IMPACTS IN THE
AREA. REGARDLESS, IN MUCH OF THE MODERATE RISK AREA, ENOUGH RAIN IS
EXPECTED FROM THE OVERNIGHT MCS TO RESULT IN SCATTERED TO NUMEROUS
INSTANCES OF FLASH FLOODING WHERE THE HEAVIEST RAINS PERSIST THE
LONGEST. THIS WILL ROUGHLY FOLLOW THE EASTERN 2/3 OF THE NE/KS
BORDER. EXPECTED RAINFALL AMOUNTS HAVE COME DOWN A BIT TOWARDS FAR
EASTERN KANSAS INTO MISSOURI, LIKELY DUE TO A BIT FASTER FORWARD
SPEED OF THE MCS'S ASSOCIATED STORMS BY THE TIME THE MCS REACHES
THAT AREA AFTER MIDNIGHT SUNDAY MORNING, SO THE MODERATE RISK WAS
TRIMMED AND THE SLIGHT IN WESTERN MISSOURI WAS TRIMMED AS WELL.
ALONG THE GULF COAST, FEW CHANGES WERE NEEDED. AS WITH TODAY,
SLOW-MOVING TRAINING CONVECTION IN THE SLIGHT RISK AREA IS LIKELY
TO IMPACT MANY AREAS OF YESTERDAY'S HIGH RISK AND TODAY'S MODERATE
RISK AREAS. SUFFICIENT DRY TIME IN BETWEEN SHOULD PREVENT THE
WIDESPREAD IMPACTS THAT WOULD NECESSITATE A MODERATE RISK UPGRADE
IN THIS AREA FOR NOW...BUT THE AREA WILL CERTAINLY NEED TO CONTINUE
TO BE MONITORED TO ENSURE THAT EXPECTED BEHAVIOR PERSISTS.
WEGMAN
..CENTRAL PLAINS AND MISSOURI VALLEY
A LARGE AREA OF HEAVY RAIN ASSOCIATED WITH A DEVELOPING MCS
STARTING SATURDAY AFTERNOON AND CONTINUING INTO SATURDAY NIGHT IS
EXPECTED TO BRING WIDESPREAD HEAVY RAINFALL ACROSS PORTIONS OF THE
CENTRAL PLAINS INTO THE MISSOURI VALLEY WITH THE GREATEST THREAT
CURRENTLY EXPECTED ACROSS SOUTHEASTERN NEBRASKA, NORTHEASTERN
KANSAS, AND FAR NORTHWESTERN MISSOURI/SOUTHWESTERN IOWA. STORMS
ARE EXPECTED TO INITIATE SATURDAY AFTERNOON WITH PEAK HEATING OVER
THE CENTRAL HIGH PLAINS AND AHEAD OF A RACING SHORTWAVE CROSSING
THE ROCKIES. MEANWHILE, A LLJ OF SOUTHEASTERLY FLOW WILL PUMP DEEP
GULF MOISTURE UP THE PLAINS THROUGH THE DAY. THIS WILL FORCE THE
DRYLINE TO RACE EASTWARD IN RESPONSE. THE WARM FRONT ASSOCIATED
WITH THE LOW AND THE DRY LINE WILL UPLIFT THE DEEP MOISTURE,
RESULTING IN WIDESPREAD SHOWER AND THUNDERSTORM DEVELOPMENT. THESE
STORMS ARE EXPECTED TO GROW UPSCALE INTO AN EXPANSIVE, ORGANIZED
CONVECTIVE SYSTEM INTO THE EVENING AND OVERNIGHT HOURS THAT WILL
THEN TRACK SOUTHEASTERLY ACROSS THE RISK AREA.
THE LATEST DETERMINISTIC GUIDANCE SHOWS AREAL AVERAGE RAINFALL
TOTALS ALONG THE EXPECTED PATH OF THE MCS IN THE 2-3" RANGE WITH
LOCALLY HIGHER AMOUNTS OF 4-6", MORE THAN SUFFICIENT TO LEAD TO
SCATTERED AND POTENTIALLY WIDESPREAD FLASH FLOODING, WHICH HAS
PROMPTED THE LEVEL 3/4 MODERATE RISK. AS IS USUALLY THE CASE WITH
CONVECTIVE SYSTEMS THE EXACT PATH AND DURATION WILL BE DETERMINED
BY MORE MESOSCALE DETAILS THAN THE GUIDANCE CAN TYPICALLY PIN DOWN
AT THIS TIME FRAME, SO SOME AREAL MODIFICATION AND POSSIBLE
EXPANSION OF THE MODERATE RISK WILL BE LIKELY OVER THE NEXT COUPLE
OF DAYS. THE MOST LIKELY AREA FOR EXPANSION WOULD BE FURTHER TO
SOUTHEAST INTO MORE OF WESTERN MISSOURI AND EAST-
CENTRAL/SOUTHEASTERN KANSAS. HOWEVER, GIVEN THE NOTED UNCERTAINTY
WITH THE EVOLUTION OF THESE TYPES OF SYSTEMS AT THIS TIMEFRAME,
HAVE LIMITED THE EXTENT OF THE RISK AREA TO ALSO OVERLAP WHERE THE
GREATEST SUPPORT/CONFIDENCE IS SHOWN BY THE ENSEMBLE
MEAN/PROBABILISTIC GUIDANCE.
..EASTERN TEXAS THROUGH THE CENTRAL GULF COAST
ONE MORE DAY OF SCATTERED SLOW-MOVING STORMS IS EXPECTED ON
SATURDAY ACROSS THE DEEP SOUTH BETWEEN EASTERN TX AND SOUTHERN
AL/FL PANHANDLE. THE LINGERING FRONTAL BOUNDARY DRAPED NORTH OF THE
GULF COAST WILL BEGIN TO LIFT NORTH DURING THE DAY AND LEAVE
CONVECTION WIDELY SCATTERED, BUT MORE FOCUSED ACTIVITY IS LIKELY
DURING THE MORNING HOURS AS HIGH PRESSURE OVER THE TENNESSEE VALLEY
KEEPS THE THERMAL/MOISTURE GRADIENT RATHER SHARP AND FOCUSES
ONGOING THUNDERSTORM ACTIVITY WITHIN PWS ABOVE 2". LINGERING MCV(S)
FROM THE DAY 1 PERIOD ACROSS EASTERN TX AND THE LOWER MISSISSIPPI
VALLEY COULD ALSO ADD LOCATIONS FOR MORE ORGANIZED THUNDERSTORM
ACTIVITY. THE SOILS IN THIS REGION ALSO REMAIN EXTREMELY SATURATED
AND SENSITIVE TO ADDITIONAL INTENSE RAINFALL RATES, LEADING TO THE
POTENTIAL FOR SCATTERED INSTANCES OF FLASH FLOODING ON SATURDAY AND
THE SLGT RISK OF EXCESSIVE RAINFALL.
SNELL
DAY 3
VALID 12Z SUN JUN 21 2026 - 12Z MON JUN 22 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN
OKLAHOMA AND THE OZARKS THROUGH MUCH OF THE MIDWEST AND OHIO
VALLEY AS WELL AS FOR PORTIONS OF SOUTH DAKOTA...
..2030Z UPDATE
ACROSS THE CENTER OF THE COUNTRY FROM THE OZARKS TO THE MIDWEST,
FEW CHANGES WERE NEEDED WITH THIS UPDATE. THE MCS FROM THE PLAINS
ON D2 CONTINUES EAST ACROSS THE MIDWEST ON D3/SUNDAY. AS IT MOVES
EAST, IT ENCOUNTERS INCREASINGLY PLENTIFUL GULF MOISTURE ALREADY IN
PLACE, WHILE THE LOW AND THE MCS ITSELF DRAW ADDITIONAL MOISTURE
ADVECTION FROM THE SOUTH INTO THE SYSTEM. THIS WILL ENSURE THE
STORMS CONTINUE RIGHT THROUGH THE PERIOD, AS THE MCS SLOWLY MOVES
EAST. AS USUAL, THE SOUTHERN END OF THE MCS APPEARS TO BE THE AREA
OF GREATEST CONCERN, AS THE STORMS ON THE SOUTH SIDE ARE THE FIRST
TO INGEST THE DEEP GULF MOISTURE OVER THE AREA. THIS WILL ENCOURAGE
THE STORMS TO LINGER AND BACKBUILD TO THE SOUTHWEST, EXTENDING THE
DURATION OF THE HEAVY RAINFALL IN THOSE AREAS. FURTHER, FFGS ACROSS
MUCH OF THE MIDWEST REMAIN DEPRESSED DUE TO RECENT HEAVY RAINFALL,
AND SOILS ARE WETTER THAN NORMAL. SOME DRYING IN BETWEEN NOW AND
SUNDAY SHOULD HELP TO MITIGATE FLOODING SOMEWHAT, BUT THE STRONGEST
STORMS SHOULD HAVE NO TROUBLE EXCEEDING THE FFGS AS 2-3 INCH/HOUR
RATES ARE EXPECTED. A MODERATE RISK REMAINS POSSIBLE. IF ONE WERE
TO BE ISSUED, IT APPEARS A BAND EXTENDING WEST TO EAST ALONG I-70
IN MISSOURI, THEN FOLLOWING I-64 ACROSS SOUTHERN ILLINOIS, INDIANA,
AND THEN EAST THROUGH CINCINNATI AND NORTHERN KENTUCKY APPEARS MOST
PROBABLE. HOWEVER, THE DETAILS OF THE STORMS AND THEIR PLACEMENT
REMAIN DIFFICULT TO PINPOINT, ESPECIALLY AS THIS REMAINS OUTSIDE OF
THE CAMS RANGE, SO ADDITIONAL CHANGES ARE LIKELY.
..SOUTH DAKOTA
AN MCS, SEPARATE FROM THE ONE GOING INTO THE MIDWEST, LIKELY GETS
STARTED ACROSS SOUTH DAKOTA SATURDAY NIGHT. WITH DRY SOILS IN THE
AREA, THE RAIN WITH THE INTIAL STORMS THEN ARE LIKELY TO BE
ABSORBED WITH ONLY ISOLATED FLOODING CONCERNS. HOWEVER, GOING INTO
SUNDAY MORNING, THE REDEVELOPMENT OF THE STORMS ACROSS THE AREA
WILL INCREASE THE FLOODING POTENTIAL IN THE AREA WITH TIME. A
SOUTHEASTERLY JET OF MOISTURE WRAPPING AROUND A LOW OVER NEBRASKA
SHOULD KEEP A CONTINUOUS SUPPLY OF MOISTURE HEADING INTO THE
STORMS, AND WITH THAT WINDFLOW WORKING COUNTER TO THE SOUTHEASTERLY
MOVEMENT OF THE STORMS, THAT SHOULD WORK TO SLOW THE STORMS'
FORWARD SPEED, WORSENING FLOODING CONCERNS. GIVEN ALL THIS AND IN
COORDINATION WITH ABR/ABERDEEN, SD AND UNR/RAPID CITY, SD FORECAST
OFFICES, A SLIGHT RISK AREA WAS INTRODUCED WITH THIS UPDATE.
WEGMAN
..PREVIOUS DISCUSSION
..MIDWEST
BY THE START OF THE DAY 3 FORECAST PERIOD A POTENT SHORTWAVE AND
RELATED SURFACE LOW ARE EXPECTED TO EJECT EASTWARD OUT OF THE
CENTRAL PLAINS INTO THE MIDWEST. THERE REMAINS SOME UNCERTAINTY
REGARDING THE SPEED AND LATITUDE OF THESE FEATURES, BUT PWS ABOVE
THE 90TH CLIMATOLOGICAL PERCENTILE (PER THE 00Z GEFS) OVERLAPPING
WITH SOILS LIKELY STILL RECOVERING FROM RECENT HEAVY RAIN IN THE
MIDWEST WILL LEAD TO AT LEAST SCATTERED FLASH FLOODING CONCERNS.
NBM PROBABILITIES FOR AT LEAST 2" ARE VERY HIGH (BETWEEN 60-80%)
AND COVER MUCH OF THE NORTHERN SLGT RISK AREA FROM MO/IA TO OH.
LOCALLY HIGHER TOTALS ARE LIKELY GIVEN THE CONVECTIVE ENVIRONMENT.
THE PROGRESSIVE NATURE OF THESE STORMS MAY END UP LIMITING THE
SEVERITY OF FLASH FLOOD IMPACTS, BUT A MDT RISK UPGRADE IS POSSIBLE
SHOULD TRAINING/BACK- BUILDING ELEMENTS BECOME MORE OBVIOUS IN THE
SHORT RANGE UPDATES, PARTICULARLY ALONG THE LEADING WARM FRONT
AHEAD OF THE PRIMARY SURFACE LOW.
..SOUTHERN PLAINS, OZARKS, AND LOWER OHIO VALLEY
THE SETUP ON SUNDAY COULD LEAD TO A SOUTHERN SECONDARY AXIS OF
HEAVIEST QPF AND FLASH FLOODING IMPACTS. THE SOUTHERN END OF THE
SATURDAY NIGHT THUNDERSTORM COMPLEX/MCS IS LIKELY TO SINK
SOUTHEASTWARD NEAR A TRAILING COLD FRONT AND IMPACT AREAS NEAR THE
OZARKS EARLY SUNDAY. THEN, THE EXPECTATION IS FOR REFORMING
SCATTERED CONVECTION DURING PEAK DAYTIME HEATING AND REORGANIZATION
OF THUNDERSTORMS OVERNIGHT SUNDAY ASSOCIATED WITH THE LLJ TO SPAN
FROM OK TO THE LOWER OHIO VALLEY, INCLUDING NORTHERN AR, SOUTHERN
MO, AND WESTERN TN/KY. THIS COMBINES FOR GUIDANCE TO CURRENTLY
DEPICT CURRENT QPF AMOUNTS OF 2-4" AND AN AVERAGE LOCALIZED MAX OF
6". THERE REMAINS OBVIOUS MESOSCALE UNCERTAINTIES AT THIS STAGE,
BUT WITH PWS NEAR THE 90TH CLIMATOLOGICAL PERCENTILE AND A
FAVORABLY ORIENTED WEST- EAST FRONTAL BOUNDARY, IT'S POSSIBLE A MDT
RISK UPGRADE MAY BE NEEDED ONCE CAMS COME INTO FORECAST RANGE. FOR
THE LOWER OHIO VALLEY IN PARTICULAR, SOME GUIDANCE ALSO HIGHLIGHTS
THUNDERSTORMS ASSOCIATED WITH THE INITIAL WARM FRONT LIFTING
NORTHWARD, WHICH COULD ADD YET ANOTHER POTENTIAL FOR SLOW-MOVING
REPEATING THUNDERSTORMS.
SNELL
DAY 4 AND DAY 5
VALID 12Z MON JUN 22 2026 - 12Z WED JUN 24 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE SOUTHERN PLAINS, LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND
CENTRAL APPALACHIANS ON DAY 4...
2030Z UPDATE...
ENSEMBLE AND DETERMINISTIC RUNS FROM THE DAYSHIFT LARGELY SUPPORTED
THE PREVIOUSLY-ISSUED EXCESSIVE RAINFALL OUTLOOK AND DISCUSSION.
CHANGES WERE MINIMNAL AND CONTINUED TO FOCUS IN THE SAME AREA.
BANN
PREVIOUS DISCUSSION...
DAY 4 CONTINUES TO AN ACTIVE PATTERN THROUGH A GOOD PORTION OF THE
CONUS, EAST OF THE MISSISSIPPI WITH A PROGRESSIVE TROUGH AXIS
PUSHING THROUGH THE GREAT LAKES AND NORTHEAST LEADING TO PERIODS OF
MODERATE TO HEAVY RAINFALL FROM THE OHIO VALLEY INTO THE MID
ATLANTIC AND NORTHEAST. AREAS OF THE NORTHEAST ARE SUBJECT TO
THUNDERSTORM PROSPECTS WITH THE BEST CHANCE FOR FLASH FLOODING
LIKELY TO OCCUR IN THE URBAN FOOTPRINT FROM PHILADELPHIA UP TO
BOSTON WITH AN EXPANSION INLAND TO THE HUDSON VALLEY DOWN THROUGH
EASTERN PA. CURRENT PROBS OFF THE LATEST ENSEMBLES AND NATIONAL
BLEND INDICATE A LARGE ZONE OF 50-80% PROBS FOR >1" ACROSS THE
AFOREMENTIONED AREA ABOVE WITH DETERMINISTIC OUTPUTS CLOSER TO
2-2.5" INTO PARTS OF SOUTHERN NEW ENGLAND. MRGL RISK INHERITED
REMAINS IN EFFECT, BUT THERE'S POTENTIAL HERE FOR AN UPGRADE AS WE
MOVE CLOSER TO THE D4 WINDOW, BUT WANT TO SEE MORE OF THE CAMS TO
MAKE THAT DECISION.
ACROSS THE SOUTHERN U.S., HEAVY PRECIPITATION WILL PRECLUDE ANOTHER
ROUND OF CONVECTION FORMING ALONG A QUASI-STATIONARY FRONT DRAPED
FROM THE SOUTHERN HIGH PLAINS TO THE SOUTHEASTERN CONUS. PROBS FOR
>1" ARE HIGHEST IN-OF THE AREAS OF EASTERN OK INTO THE LOWER
MISSISSIPPI AND SOUTHWESTERN TENNESSEE VALLEYS. ELEVATED THETA_E'S
AND PWAT ANOMALIES +2 DEV. OR GREATER INDICATE A FORMIDABLE
ENVIRONMENT CAPABLE OF CONTINUED HEAVY RAIN POTENTIAL THAT WILL
LIKELY PRODUCE RAINFALL OF 2-4", AT LEAST IN SOME OF THE
THUNDERSTORM ACTIVITY THAT DEVELOPS. THE FOCAL POINT ALONG THE
FRONT WILL LIKELY BE WHERE THE HEAVIEST RAIN WILL OCCUR, OR AT
LEAST BE A LOW-LEVEL CONVERGENCE MECHANISM THAT CAN ENHANCE
REGIONAL CONVECTION. THERE'S HIGH ENOUGH CONFIDENCE IN THE LOCATION
OF CONVECTION FOR THE D4 PERIOD TO OVERLAP WITH AREAS THAT WILL
HAVE SEEN SEVERAL INCHES THE PERIODS PRIOR WHICH LED TO AN UPGRADE
TO A SLGT RISK POSITIONED OVER PORTIONS OF THE SOUTHERN PLAINS
THROUGH PARTS OF THE LOWER MISSISSIPPI AND NEIGHBORING TENNESSEE
VALLEYS. THE RISK EXTENDS THROUGH THE SMOKEY MOUNTAINS UP INTO
PARTS OF THE CENTRAL APPALACHIANS IN EASTERN KY UP INTO WV AS THE
CONVERGENCE REGIME FOLLOWS THE FRONTAL POSITIONING OVER THESE
AREAS.
DAY 5 IS A TRANSITION PERIOD INTO A MORE TYPICAL SUMMER TIME REGIME
FOR THE CONUS WITH A LONGWAVE TROUGH OVER THE NORTHERN U.S. AND A
DOME OF MID AND UPPER RIDGING POSITIONING ITSELF ACROSS THE
SOUTHWEST. THIS WILL CAUSE A PERSISTENT NORTHWESTERLY FLOW PATTERN
ACROSS THE CENTRAL AND SOUTHERN HIGH PLAINS OVER INTO THE LOWER
MISSISSIPPI VALLEY AS PROGRESSIVE SHORTWAVE PULSES EJECT OUT OF THE
ROCKIES AND RIDE THE PREVAILING NORTHWESTERIES IN PLACE BETWEEN THE
RIDGE AND TROUGH. THIS HIGHLIGHTS POTENTIAL FOR MCS DEVELOPMENT AND
FLASH FLOODING SCENARIOS FROM THE FRONT RANGE AND POINTS SOUTHEAST
AS THE STEERING FLOW ORIENTS BETWEEN THE BASE OF THE TROUGH AND THE
NORTHEASTERN FLANK OF THE RIDGE. THIS IS HISTORICALLY PROJECTING A
CASE OF THUNDERSTORM MATURATION AND UPSCALE GROWTH OVER THE AREA
BETWEEN CO/KS DOWN THROUGH OK/TX WITH POTENTIALLY THE RED RIVER
BASIN AS A FOCUS FOR THUNDERSTORM ACTIVITY. EVENTUALLY THIS ENDS UP
MIGRATING INTO THE ARKLATEX AND/OR LOWER MISSISSIPPI AREA WHICH IS
SHOWING UP IN THE QPF FOOTPRINT ON ENSEMBLES. WITH THIS BECOMING A
MORE STABLE SIGNAL IN THE GLOBAL ENSEMBLES AND ALIGNING WITH THE
NBM QPF OUTPUT, A MRGL RISK WAS ADDED TO THE NEW D5 TO ACCOUNT FOR
THIS POTENTIAL EVOLUTION.
KLEEBAUER
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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