814
FXUS01 KWBC 270809
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 AM EDT TUE AUG 27 2024
VALID 12Z TUE AUG 27 2024 - 12Z THU AUG 29 2024
...A BRIEF SPELL OF RECORD HEAT EXPECTED TO SPREAD FROM THE
MIDWEST TO THE EAST COAST...
...ACTIVE SHOWERS AND SEVERE THUNDERSTORMS THIS MORNING ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST/GREAT LAKES WILL SHIFT EASTWARD
INTO THE NORTHERN MID-ATLANTIC/SOUTHERN NEW ENGLAND BY LATE
WEDNESDAY INTO EARLY THURSDAY...
...FIRST SNOWFLAKES OF THE SEASON COULD REACH THE HIGHER
ELEVATIONS OF NORTHWESTERN MONTANA ON WEDNESDAY FOLLOWED BY A
CHANCE OF SEVERE THUNDERSTORMS ACROSS NORTH DAKOTA WEDNESDAY
NIGHT/EARLY THURSDAY...
THE CLOSED UPPER HIGH CURRENTLY CENTERED OVER THE MID-MISSISSIPPI
VALLEY WILL BE EXPANDING EASTWARD OVER THE NEXT TWO DAYS,
SPREADING INTO LARGE PORTIONS OF THE EAST COAST FROM THE
MID-ATLANTIC SOUTHWARD. THIS WILL SEND A QUICK SPELL OF
POTENTIALLY RECORD HIGH TEMPERATURES FROM THE MIDWEST INTO THE
OHIO VALLEY, TENNESSEE VALLEY, SOUTHERN TO CENTRAL APPALACHIANS
AND INTO THE MID-ATLANTIC. THE COMBINATION OF HOT TEMPERATURES IN
THE MID TO UPPER 90S TO NEAR 100 DEGREES TOGETHER WITH HIGH
HUMIDITY LEVELS WILL PRODUCE MAXIMUM DAILY HEAT INDICES OF BETWEEN
105 AND 115 DEGREES ACROSS THESE REGIONS, WITH HEAT RISKS REACHING
MAJOR TO EXTREME LEVELS TODAY ACROSS THE MIDWEST INTO LOWER GREAT
LAKES. EXCESSIVE HEAT WARNINGS AND HEAT ADVISORIES ARE CURRENTLY
IN EFFECT ACROSS THE MID TO UPPER MISSISSIPPI VALLEY, THE MIDWEST
AND SOUTHERN NEW ENGLAND, AFFECTING NEARLY 61 MILLION PEOPLE, WITH
FURTHER EXPANSION OF THESE WARNINGS AND ADVISORIES POSSIBLE INTO
PORTIONS OF THE MID-ATLANTIC FOR WEDNESDAY. THIS SPELL OF RECORD
HEAT WILL BE RELATIVELY SHORT-LIVED AS A COOL HIGH PRESSURE SYSTEM
SETTLING INTO SOUTHERN CANADA IS FORECAST TO SEND A COOL AND DAMP
AIR MASS INTO THE GREAT LAKES ON WEDNESDAY AND WILL QUICKLY
OVERSPREAD NEW ENGLAND WEDNESDAY NIGHT, REACHING INTO THE
MID-ATLANTIC BY THURSDAY MORNING BEHIND A SHARP COLD FRONT.
AROUND THE PERIPHERIES OF THE ABOVE MENTIONED UPPER HIGH,
PRECIPITATION IS LIKELY TO BE ACTIVE ALONG THE GULF COAST AND FROM
PORTIONS OF THE SOUTHWEST, NORTHEASTWARD INTO THE CENTRAL PLAINS,
UPPER MISSISSIPPI VALLEY, UPPER GREAT LAKES INTO NORTHERN NEW
ENGLAND IN THIS "RING OF FIRE". IN THESE REGIONS, MOISTURE VALUES
ARE FORECAST TO REMAIN ABOVE AVERAGE, SUPPORTING THE POTENTIAL FOR
AREAS OF ACTIVE THUNDERSTORMS, HEAVY RAINS AND FLASH FLOODING.
ACTIVE SHOWERS AND SEVERE THUNDERSTORMS THIS MORNING ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST/GREAT LAKES COULD RESULT IN
AREAS OF HEAVY RAINS AND FLASH FLOODING. SOME OF THESE
THUNDERSTORMS ARE EXPECTED TO SHIFT EASTWARD INTO THE NORTHERN NEW
ENGLAND BY EARLY WEDNESDAY, BEFORE SOME ADDITIONAL STRONG TO
SEVERE THUNDERSTORMS AND HEAVY RAIN POSSIBLE ACROSS PORTIONS OF
THE UPPER OHIO VALLEY, CENTRAL APPALACHIANS AND INTO THE
MID-ATLANTIC LATER ON WEDNESDAY INTO EARLY THURSDAY AHEAD OF THE
SHARP COLD FRONT.
WHILE MUCH ABOVE TO RECORD HIGH TEMPERATURES DOMINATE PORTIONS OF
THE CENTRAL TO EASTERN U.S. INTO MID WEEK, ANOTHER STRONG FRONT
WILL BE PUSHING INLAND INTO THE PACIFIC NORTHWEST FOLLOWED BY THE
NORTHERN ROCKIES AND INTO THE NORTHERN HIGH PLAINS BY THIS
EVENING. MUCH BELOW AVERAGE TEMPERATURES IN THE WAKE OF THIS
FRONT WILL LIKELY SPREAD ACROSS THE PACIFIC NORTHWEST FOR TODAY
AND INTO THE NORTHERN ROCKIES/NORTHERN HIGH PLAINS ON WEDNESDAY
WITH HIGH TEMPERATURES 10 TO 20 DEGREES BELOW AVERAGE. THERE IS
NOT EXPECTED TO BE A LOT OF PRECIPITATION WITH THIS FRONT OVER THE
NORTHWEST, BUT THE FALLING TEMPERATURES COULD BRING THE FIRST
SNOWFLAKES OF THE SEASON FOR THE HIGHER ELEVATIONS OF NORTHWESTERN
MONTANA ON WEDNESDAY. BY WEDNESDAY NIGHT INTO EARLY THURSDAY, A
CHANCE OF SEVERE THUNDERSTORMS WILL BE MOVING EASTWARD ACROSS
NORTH DAKOTA AHEAD OF THE STRONG COLD FRONT.
KONG/ORAVEC
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