367
FXUS01 KWBC 200801
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 AM EDT MON MAY 20 2024
VALID 12Z MON MAY 20 2024 - 12Z WED MAY 22 2024
...CONTINUED SEVERE WEATHER AND EXCESSIVE RAINFALL THREATS OVER
THE CENTRAL U.S. INTO MID-WEEK...
...COOL CONDITIONS WITH PERIODS OF SHOWER AND STORM CHANCES FROM
THE ROCKIES TO THE PACIFIC NORTHWEST...
...WELL ABOVE AVERAGE, SUMMER-LIKE TEMPERATURES TO START THE WEEK
ACROSS MUCH OF THE CENTRAL/EASTERN U.S....
AN ENERGETIC UPPER-LEVEL PATTERN FEATURING MULTIPLE SHORTWAVES
EMITTING FROM A BROADER LONG-WAVE TROUGH OVER THE WESTERN U.S.
WILL CONTINUE A PERIOD OF ACTIVE WEATHER OVER THE CENTRAL U.S.
THIS WEEK. AN INITIAL SHORTWAVE/ACCOMPANYING SURFACE FRONTAL
SYSTEM WILL BRING SHOWERS AND THUNDERSTORMS TO PORTIONS OF THE
UPPER MIDWEST/GREAT LAKES REGION BY EARLY MONDAY. A FEW MORE
ROBUST THUNDERSTORMS WILL BE POSSIBLE IMMEDIATELY AHEAD OF THE
WAVE OVER NORTHEASTERN ILLINOIS AND ADJACENT WISCONSIN/INDIANA,
WHERE THE STORM PREDICTION CENTER HAS ISSUED A SLIGHT RISK OF
SEVERE WEATHER (LEVEL 2/5) FOR THE THREAT OF SOME DAMAGING WINDS
AND LARGE HAIL. SOME LOCALLY HEAVY DOWNPOURS AND ISOLATED FLASH
FLOODING WILL ALSO BE POSSIBLE. FURTHER WEST, LEE CYCLOGENESIS IS
EXPECTED OVER THE CENTRAL HIGH PLAINS AS THE LONG-WAVE TROUGH
FURTHER AMPLIFIES, HELPING TO REINFORCE A FRONTAL BOUNDARY DRAPED
ACROSS THE REGION. MOIST UPSLOPE FLOW NORTH OF THIS BOUNDARY IS
EXPECTED TO LEAD TO THUNDERSTORMS BY MONDAY AFTERNOON, WITH AN
ENHANCED RISK OF SEVERE WEATHER (LEVEL 3/5) OVER NORTHEASTERN
COLORADO AND SOUTHWESTERN NEBRASKA AS SOME OF THE MORE ROBUST
STORMS MAY PRODUCE VERY LARGE HAIL, SIGNIFICANT DAMAGING WINDS,
AND A FEW TORNADOES. A BROADER SLIGHT RISK EXTENDS NORTHEASTWARD
ALONG THE FRONT THROUGH THE CENTRAL PLAINS INTO THE UPPER MIDWEST.
INCREASING STORM COVERAGE MONDAY EVENING WITH THE POTENTIAL FOR
SOME LOCALLY HEAVY DOWNPOURS WILL ALSO BRING THE THREAT FOR SOME
ISOLATED FLASH FLOODING FROM NORTHEASTERN COLORADO NORTHEAST INTO
NORTHWESTERN IOWA. MOISTURE SPREADING NORTHWESTWARD INTO PORTIONS
OF THE NORTHERN HIGH PLAINS/ROCKIES WILL BRING MODERATE
PRECIPITATION CHANCES HERE AS WELL, WITH SOME LOCALLY HEAVY
SNOWFALL TOTALS POSSIBLE FOR HIGHER MOUNTAIN ELEVATIONS.
ANOTHER SHORTWAVE EJECTING FROM THE LONGWAVE WESTERN TROUGH WILL
BRING A BROADER, GREATER CHANCE FOR SEVERE WEATHER AND FLASH
FLOODING TO PORTIONS OF THE MIDWEST TUESDAY. THE ACCOMPANYING
SURFACE LOW PRESSURE/FRONTAL SYSTEM WILL DEEPEN AND LIFT
NORTHEASTWARD FROM THE PLAINS INTO THE UPPER MIDWEST, WITH AN
EXPANSIVE WARM SECTOR FROM THE SOUTHERN PLAINS NORTHEASTWARD
THROUGH THE LOWER MISSOURI AND UPPER MISSISSIPPI VALLEYS. BOTH
SUPERCELLS AND MORE ORGANIZED CONVECTIVE SYSTEMS ARE EXPECTED
AMIDST STRENGTHENING LOW AND UPPER-LEVEL WIND FIELDS AND STRONG
INSTABILITY. AN ENHANCED RISK OF SEVERE WEATHER IS IN PLACE FOR
THE THREAT OF TORNADOES, SOME STRONG, SIGNIFICANT DAMAGING WINDS,
AND LARGE HAIL. IN ADDITION, A DEEP INFLUX OF MOISTURE AS WELL AS
THE STRONG FORCING ASSOCIATED WITH THE DEEP SURFACE LOW WILL HELP
TO PROMOTE HEAVY DOWNPOURS. WITH MORE NUMEROUS STORMS EXPECTED IN
VICINITY OF THE SURFACE LOW, A SLIGHT RISK OF EXCESSIVE RAINFALL
(LEVEL 2/4) HAS BEEN ISSUED FOR PORTIONS OF CENTRAL/SOUTHERN
MINNESOTA AND NORTHWESTERN WISCONSIN FOR THE RISK OF SOME
SCATTERED INSTANCES OF FLASH FLOODING. LINGERING SHOWER AND
THUNDERSTORM CHANCES WILL ALSO EXTEND BACK WEST THROUGH THE
CENTRAL PLAINS INTO THE CENTRAL/NORTHERN ROCKIES.
ELSEWHERE, A FEW THUNDERSTORMS WILL REMAIN POSSIBLE OVER THE
FLORIDA PENINSULA THROUGH AT LEAST TUESDAY. AN UPPER-LOW/FRONTAL
SYSTEM DROPPING SOUTHWARD FROM NORTHWESTERN CANADA WILL SPREAD
SHOWERS AND STORMS INTO THE PACIFIC NORTHWEST/NORTHERN GREAT BASIN
TUESDAY, WITH SOME LOCALLY HEAVY RAINFALL POSSIBLE ALONG THE
COASTAL RANGES AND CASCADES. A BROAD AREA OF WELL ABOVE AVERAGE
TEMPERATURES IS EXPECTED OVER MUCH OF THE CENTRAL/EASTERN U.S.
WITH RIDGING IN PLACE AHEAD OF THE TROUGH OVER THE WEST. HIGHS IN
THE 80S AND EVEN LOW 90S WILL BE COMMON, EVEN IN MORE NORTHERLY
LOCATIONS FROM THE GREAT LAKES INTO THE NORTHEAST. SWELTERING HEAT
CONTINUES OVER PORTIONS OF SOUTHERN TEXAS INTO THE SOUTHERN HIGH
PLAINS AS HIGHS SOAR INTO THE 90S AND 100S. IN CONTRAST, MUCH
COOLER, BELOW AVERAGE TEMPERATURES ARE EXPECTED TO THE NORTH AND
WEST OF THE SYSTEM OVER THE PLAINS UNDER THE INFLUENCE OF THE
WESTERN TROUGH. HIGHS FROM THE PACIFIC NORTHWEST INTO THE GREAT
BASIN, NORTHERN/CENTRAL ROCKIES, AND NORTHERN/CENTRAL PLAINS WILL
BE IN THE 50S AND 60S. HIGHS WILL BE CLOSER TO AVERAGE IN THE
SOUTHWEST WITH 80S AND 90S FORECAST.
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