921
FXUS01 KWBC 171958
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
358 PM EDT TUE SEP 17 2024
VALID 00Z WED SEP 18 2024 - 00Z FRI SEP 20 2024
...A COASTAL LOW BRINGS A THREAT OF FLASH FLOODING TO THE
MID-ATLANTIC TODAY WITH PRECIPIATION CHANCES LINGERING THROUGH
WEDNESDAY...
...A STRONG LOW PRESSURE SYSTEM WILL BRING UNSETTLED WEATHER TO
THE NORTHERN/CENTRAL ROCKIES AND PLAINS WITH SEVERE THUNDERSTORMS
EXPECTED THIS EVENING IN THE NORTHERN/CENTRAL HIGH PLAINS...
...VERY HEAVY RAINFALL EXPECTED IN MONTANA ON WEDNESDAY WITH SOME
FLASH FLOODING POSSIBLE...
AN AREA OF LOW PRESSURE, PREVIOUSLY LABELED AS POTENTIAL TROPICAL
CYCLONE EIGHT, WILL CONTINUE TO SLOWLY MOVE NORTH ACROSS THE
CAROLINAS TOWARDS THE MID-ATLANTIC OVER THE NEXT DAY OR SO. MOIST,
ONSHORE FLOW WILL SUPPORT PERSISTENT SHOWERS AND THUNDERSTORMS
ACROSS PORTIONS OF NORTH CAROLINA AND THE SOUTHERN MID-ATLANTIC
THROUGH EARLY WEDNESDAY, AND LOCALLY HEAVY RAINFALL COULD RESULT
IN ISOLATED TO SCATTERED INSTANCES OF FLASH FLOODING. FLOOD
WATCHES ARE IN EFFECT FOR PORTIONS OF SOUTHEASTERN VIRGINIA AND
NORTH CAROLINA. PRECIPITATION CHANCES WILL EXPAND NORTHEASTWARD
INTO SOUTHERN NEW ENGLAND THROUGH THE DAY WEDNESDAY, THOUGH
INTENSITY SHOULD BEGIN TO DECREASE OVERALL, RESULTING IN A LOWER
THREAT FOR FLASH FLOODING. COASTAL FLOODING WILL ALSO BE A CONCERN
WITH A PROLONGED PERIOD OF ONSHORE WINDS ALONG THE MID-ATLANTIC
COAST. BY THURSDAY, THIS SYSTEM WILL BEGIN TO SHIFT OFFSHORE INTO
THE ATLANTIC AND HIGH PRESSURE WILL BUILD BEHIND IT.
MEANWHILE, A STRONG LOW PRESSURE SYSTEM MOVING ACROSS THE
INTERMOUNTAIN WEST THIS AFTERNOON WILL BEGIN TO EMERGE INTO THE
NORTHERN/CENTRAL PLAINS THIS EVENING, STRENGTHENING IN THE LEE OF
THE ROCKIES. WIDESPREAD SHOWERS AND THUNDERSTORMS ARE FORECAST
WITH THIS SYSTEM IN THE VICINITY OF THE LOW PRESSURE CENTER AND
ALONG AND AHEAD OF THE TRAILING COLD FRONT. SOME THUNDERSTORMS MAY
BECOME SEVERE THIS EVENING IN THE NORTHERN AND CENTRAL HIGH
PLAINS, AND THE STORM PREDICTION CENTER HAS HIGHLIGHTED THIS AREA
WITH A SLIGHT RISK OF SEVERE THUNDERSTORMS (LEVEL 2/5) WITH AN
EMBEDDED ENHANCED RISK (LEVEL 3/5) OVER THE CENTRAL HIGH PLAINS.
SEVERE STORM HAZARDS INCLUDE SIGNIFICANT DAMAGING WINDS AND
ISOLATED LARGE HAIL.
FURTHER NORTH, ANOMALOUSLY MOIST, STRONG EASTERLY UPSLOPE FLOW
ALONG THE NORTHERN ROCKIES WILL LEAD TO THUNDERSTORMS AND VERY
HEAVY RAINFALL TONIGHT AND ESPECIALLY ON WEDNESDAY. A SLIGHT RISK
OF EXCESSIVE RAINFALL (LEVEL 2/4) COVERS PORTIONS OF NORTH-CENTRAL
MONTANA WHERE SEVERAL INCHES OF RAIN (2-4"+) ARE POSSIBLE, LEADING
TO A HEIGHTENED RISK OF FLOODING. WINDS ARE ALSO EXPECTED TO BE
RATHER GUSTY AS THE LOW STRENGTHENS, PROMPTING SOME HIGH
WIND-RELATED WARNINGS AND ADVISORIES FOR PORTIONS OF THE NORTHERN
HIGH PLAINS. GUSTS AS HIGH AS 60 MPH WILL BE POSSIBLE,
PARTICULARLY ALONG THE FRONT RANGE OF THE ROCKIES. ADDITIONAL
ISOLATED THUNDERSTORMS ARE EXPECTED AHEAD OF THE EASTWARD MOVING
COLD FRONT THROUGH THE PLAINS ON WEDNESDAY AND INTO THE UPPER
MIDWEST BY LATE WEDNESDAY AND INTO THURSDAY. MORE FAVORABLE
OVERLAP OF STRONG UPPER-LEVEL WINDS WITH AN ACCOMPANYING TROUGH
AND INCREASED MOISTURE/INSTABILITY WILL LEAD TO THE THREAT OF SOME
ADDITIONAL SEVERE WEATHER THURSDAY. THERE IS A SLIGHT RISK OVER
PORTIONS OF EASTERN MINNESOTA, NORTHWESTERN WISCONSIN, AND
NORTHERN IOWA FOR ISOLATED LARGE HAIL AND DAMAGING WINDS.
ANOTHER SYSTEM APPROACHING THE PACIFIC COAST WILL BRING SOME
SCATTERED SHOWERS AND STORMS TO THE COASTAL PACIFIC NORTHWEST THIS
EVENING, SPREADING SOUTHWARD INTO NORTHERN CALIFORNIA AND THE
CENTRAL GREAT BASIN ON WEDNESDAY. THE RAIN WILL BE RELATIVELY
MODEST FOR MOST AREAS, WITH THE HIGHEST EXPECTED IN THE SIERRAS,
WHERE A BIT OF SNOW MAY MIX IN AT THE HIGHER ELEVATIONS.
TEMPERATURE-WISE, MUCH OF THE NORTHERN-TIER OF THE CENTRAL/EASTERN
U.S. AS WELL AS THE PLAINS WILL REMAIN MUCH ABOVE AVERAGE
WEDNESDAY AND THURSDAY. HIGHS WILL BE INTO THE MID- TO UPPER 80S
FOR PORTIONS OF NORTHERN NEW ENGLAND AND THE UPPER MIDWEST
WEDNESDAY, AND A HANDFUL OF NEAR RECORD-TYING/BREAKING HIGHS
APPROACHING 100 WILL BE POSSIBLE FOR PORTIONS OF THE SOUTHERN
PLAINS ON THURSDAY. MEANWHILE, TEMPERATURES WILL BE WELL BELOW
AVERAGE ACROSS THE WEST BEHIND THE STRONG PLAINS SYSTEM, WITH MANY
HIGHS IN THE 60S ACROSS THE GREAT BASIN AND ONLY IN THE 80S FOR
PORTIONS OF THE DESERT SOUTHWEST. HIGHS WILL GENERALLY BE NEAR
AVERAGE IN THE SOUTHEAST (80S-90S) AND MID-ATLANTIC (70S-80S) THE
NEXT COUPLE OF DAYS.
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