397
FXUS01 KWBC 120801
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 AM EDT SAT AUG 12 2023
VALID 12Z SAT AUG 12 2023 - 12Z MON AUG 14 2023
...DANGEROUS HEAT WILL PERSIST ACROSS MUCH OF THE SOUTH THROUGH
THIS WEEKEND, WITH ANOTHER HEAT WAVE 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...
DANGEROUS HEAT WILL CONTINUE FOR MUCH OF THE SOUTHERN U.S. THROUGH
THE WEEKEND AS A WEST TO EAST ORIENTED UPPER-LEVEL RIDGE OF HIGH
PRESSURE REMAINS IN PLACE. WIDESPREAD HEAT-RELATED ADVISORIES AND
WARNINGS ARE IN EFFECT FROM FLORIDA WEST THROUGH THE GULF COAST
AND INTO THE LOWER MISSISSIPPI VALLEY AND SOUTHERN PLAINS, WITH
THE MOST EXCESSIVE HEAT EXPECTED OVER PORTIONS OF TEXAS AND THE
LOWER MISSISSIPPI VALLEY. FORECAST HIGHS THIS WEEKEND WILL 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. WHEN
COMBINED WITH HIGH HUMIDITY VALUES, HEAT INDICES WILL REACH AS
HIGH 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. THE HEAT WAVE
LOOKS TO CONTINUE BEYOND THE CURRENT FORECAST PERIOD INTO NEXT
WEEK. UNFORTUNATELY, A NEW HEAT WAVE IS ALSO FORECAST TO BEGIN
BUILDING ACROSS THE PACIFIC NORTHWEST BY SUNDAY AS A STRONG RIDGE
OF HIGH PRESSURE SETTLES 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 BRING SHOWER
AND STORM CHANCES TO THE NORTHEAST/MIDWEST/PLAINS THIS WEEKEND. AN
INITIAL FRONTAL SYSTEM WILL PUSH EASTWARD ACROSS THE GREAT
LAKES/MIDWEST INTO THE NORTHEAST THROUGH SATURDAY EVENING,
FOCUSING STORM DEVELOPMENT OVER PORTIONS OF THE NORTHEAST INTO THE
OHIO VALLEY. 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. HIGHS WILL GENERALLY BE AT
OR JUST ABOVE AVERAGE FOR MUCH OF THE CENTRAL/NORTHERN PLAINS
SATURDAY, WITH UPPER 80S TO LOW 90S FORECAST. MUCH COOLER
TEMPERATURES WILL FOLLOW THE PASSAGE OF THE FRONTAL SYSTEMS SUNDAY
OVER THE NORTHERN PLAINS WITH HIGHS DROPPING INTO THE UPPER 60S TO
LOW 70S. OVER THE WEST, 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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