551
FXUS01 KWBC 122003
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
402 PM EDT SAT AUG 12 2023
VALID 00Z SUN AUG 13 2023 - 00Z TUE AUG 15 2023
...DANGEROUS HEAT PERSISTS ACROSS MUCH OF THE SOUTH WHILE ANOTHER
HEAT WAVE IS EXPECTED TO DEVELOP ACROSS THE PACIFIC NORTHWEST
SUNDAY...
...SEVERE THUNDERSTORMS AND FLASH FLOODING POSSIBLE SATURDAY FOR
PARTS OF THE OHIO VALLEY AND NORTHEAST, SHIFTING TO THE PLAINS AND
MISSISSIPPI VALLEY SUNDAY...
...HEAVY RAINFALL EXPECTED FOR THE HIGH PLAINS LATE SATURDAY WITH
MONSOONAL SHOWERS EXPECTED ACROSS THE FOUR CORNERS REGION...
A BROAD UPPER-LEVEL RIDGE ANCHORED OVER THE SOUTH WILL KEEP
DANGEROUS HEAT IN PLACE THIS WEEKEND AND INTO EARLY NEXT WEEK.
WIDESPREAD HEAT-RELATED ADVISORIES AND WARNINGS ARE IN EFFECT FROM
FLORIDA NORTH TO THE CAROLINAS AND WEST TO TEXAS/OKLAHOMA. THE
MOST EXCESSIVE HEAT IS EXPECTED TO FOCUS ACROSS A LARGE PORTION OF
TEXAS INTO THE LOWER MISSISSIPPI VALLEY. DAILY HIGH TEMPERATURES
ARE FORECAST TO RANGE FROM THE MID-90S IN FLORIDA, THE UPPER 90S
INTO PORTIONS OF THE SOUTHEAST, THE LOW 100S IN OKLAHOMA AND THE
LOWER MISSISSIPPI VALLEY, AND THE MID 100S TO 110 INTO PORTIONS OF
TEXAS. THESE TEMPERATURES WHEN COMBINED WITH HIGH HUMIDITY ILL
ALLOW HEAT INDICES TO RISE AS MUCH AS 110 TO 120F FOR MANY
LOCATIONS. NUMEROUS RECORD-TYING/BREAKING HIGHS ARE FORECAST BOTH
DAYS, WITH SIMILARLY RECORD-LEVEL WARM LOW TEMPERATURES IN THE
UPPER 70S TO LOW 80S PROVIDING LITTLE RELIEF FROM THE HEAT
OVERNIGHT. THIS HEAT STREAK WILL PERSIST INTO THE COMING WEEK WITH
LITTLE TO NO REPRIEVE. ADDITIONALLY, A NEW HEATWAVE WILL BEGIN TO
DEVELOP SUNDAY ACROSS THE PACIFIC NORTHWEST THANKS TO A STRONG
RIDGE OF HIGH PRESSURE THAT WILL SETTLE IN OVERHEAD. THE MORE
EXCESSIVE TEMPERATURES WILL INITIALLY BE FOCUSED ALONG THE
INTERIOR VALLEYS WEST OF THE CASCADES, WITH HIGHS SOARING INTO THE
UPPER 90S TO MID-100S. THIS HEAT WAVE WILL ALSO CONTINUE TO
INTENSIFY AND EXPAND ACROSS THE REGION NEXT WEEK.
ENERGETIC FLOW WITH EMBEDDED SHORTWAVES NORTH OF THE RIDGE AND THE
PASSAGE OF MULTIPLE MEANDERING FRONTAL SYSTEMS WILL CONVECTION
POTENTIAL TO THE NORTHEAST/MIDWEST/PLAINS THIS WEEKEND. THE
LEADING FRONT TRACKING EASTWARD ACROSS THE GREAT LAKES/MIDWEST
INTO THE NORTHEAST THROUGH SATURDAY EVENING FOCUSING SHOWERS AND
THUNDERSTORMS FROM THE OHIO VALLEY TO THE NORTHEAST. THE STORM
PREDICTION CENTER HAS ISSUED AN ENHANCED RISK OF SEVERE WEATHER
(LEVEL 3/5) AS STRONG FLOW AT LOW LEVELS AND ALOFT WILL PROVIDE
ENOUGH SHEAR FOR STORMS TO PRODUCE DAMAGING WINDS, ALONG WITH SOME
HAIL AND THE THREAT OF A FEW TORNADOES. SOME LOCALLY HEAVY
DOWNPOURS ARE ALSO POSSIBLE, WITH A SLIGHT RISK OF EXCESSIVE
RAINFALL (LEVEL 2/4) OVER PORTIONS OF SOUTHERN NEW ENGLAND WHERE
THE GREATEST THREAT OF SOME SCATTERED INSTANCES OF FLASH FLOODING
WILL EXIST. A SHORTWAVE DROPPING SOUTH OVER THE NORTHERN PLAINS
FROM CANADA WILL HELP TO BETTER ORGANIZE A SOUTHWARD MOVING
FRONTAL SYSTEM LATE SATURDAY INTO EARLY SUNDAY WITH STORM CHANCES
SHIFTING SOUTHEASTWARD INTO THE CENTRAL/SOUTHERN PLAINS AND THE
MIDDLE MISSISSIPPI VALLEY THROUGH THE DAY SUNDAY. HIGH SURFACE
MOISTURE POOLING BETWEEN THIS FRONTAL SYSTEM AND ANOTHER FRONT TO
THE SOUTH WILL HELP STORMS TO PRODUCE SOME LOCALLY VERY HEAVY
DOWNPOURS. THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN EFFECT
FOR THE RISK OF FLASH FLOODING, PARTICULARLY IF STORMS GROW
UPSCALE INTO A MORE ORGANIZED CONVECTIVE SYSTEM SUNDAY NIGHT,
ENHANCING RAINFALL TOTALS AND COVERAGE. IN ADDITION, STRONG
BUOYANCY AND SUFFICIENT DEEP LAYER SHEAR WILL ALSO LEAD TO THE
THREAT OF SOME SEVERE WEATHER, WITH A SLIGHT RISK IN PLACE FOR THE
THREAT OF DAMAGING WINDS, LARGE HAIL, AND A FEW TORNADOES.
FORECAST HIGHS WILL RANGE FROM THE UPPER 70S TO LOW 80S IN NEW
ENGLAND TO THE MID-80S TO LOW 90S FOR THE MID-ATLANTIC AND OHIO
VALLEY WEST INTO PORTIONS OF THE MIDWEST/MISSISSIPPI VALLEY.
AREAS OF SHOWERS AND THUNDERSTORMS ARE ALSO EXPECTED ON SATURDAY
OVER PORTIONS OF THE CENTRAL AND SOUTHERN HIGH PLAINS AS A COLD
FRONT SAGS SOUTHWARD ACROSS THE REGION AND MOIST, UPSLOPE FLOW
SETTLES IN PLACE. AN ADDITIONAL SLIGHT RISK OF EXCESSIVE RAINFALL
IS IN EFFECT HERE AS WELL AS UPSCALE GROWTH OF STORMS LATER IN THE
EVENING MAY LEAD TO SOME MORE WIDESPREAD, HIGHER RAINFALL TOTALS
AND A FEW INSTANCES OF FLASH FLOODING. DAILY MAXIMUM TEMPERATURES
ARE FORECAST TO BE NEAR OR JUST ABOVE SEASONAL NORMAL FOR THE
CENTRAL AND NORTHERN PLAINS REGION WITH UPPER 80S TO LOWER 90S.
ONCE THE COLD FRONT PASSES MUCH COOLER AIR WILL FILTER IN
RESULTING IN MAXIMUM TEMPERATURES IN THE UPPER 60S TO LOW 70S.
MONSOONAL MOISTURE IN THE FOUR CORNERS REGION WILL LEAD TO DAILY
ROUNDS OF AFTERNOON THUNDERSTORMS WITH A FEW LOCALLY HEAVY
DOWNPOURS POSSIBLE, AND SOME ISOLATED CONCERNS FOR FLASH FLOODING.
THIS WILL ALSO HELP TO KEEP TEMPERATURES A BIT BELOW AVERAGE, WITH
HIGHS ONLY INTO THE UPPER 70S FOR SOME LOCATIONS. AREAS OF THE
CENTRAL/SOUTHERN ROCKIES AND GREAT BASIN WILL BE A BIT CLOSER TO
AVERAGE, SEEING HIGHS IN THE MID-80S TO LOW 90S, WITH UPPER-90S TO
MID-100S FOR THE DESERT SOUTHWEST. A LINGERING UPPER-LEVEL LOW
WILL KEEP TEMPERATURES UNSEASONABLY COOL OVER PORTIONS OF SOUTHERN
CALIFORNIA, AS HIGHS ARE EXPECTED TO BE IN THE UPPER 60S TO
MID-70S FOR THE COAST. HIGHS WILL WARM UP THROUGH THE WEEKEND
FURTHER NORTH, WITH 70S ALONG THE COAST AND 90S FOR THE INTERIOR
VALLEYS. SOME LOCALLY HEAVY SHOWERS WILL BE POSSIBLE OVER THE
SIERRA.
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