827
FXUS01 KWBC 130733
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
333 AM EDT THU JUL 13 2023
VALID 12Z THU JUL 13 2023 - 12Z SAT JUL 15 2023
...HEAVY RAIN AND FLASH FLOOD POTENTIAL RETURNS TO THE NORTHEAST
THURSDAY AND FRIDAY...
...ADDITIONAL ROUNDS OF SEVERE WEATHER AND FLASH FLOODING PERSIST
ACROSS THE MISSISSIPPI VALLEY AND PLAINS OVER THE NEXT COUPLE
DAYS...
...SIGNIFICANT HEAT WAVE CONTINUES TO EXPAND ACROSS MUCH OF THE
WESTERN AND SOUTHERN TIER OF THE U.S....
SHORTWAVE ENERGY ROTATING AROUND A BROAD UPPER-LEVEL LOW OVER THE
HUDSON BAY WILL LEAD TO INCREASED LIFT AHEAD OF A COLD FRONT
PUSHING INTO THE OHIO VALLEY AND NORTHEAST FROM THE WEST,
TRIGGERING RENEWED DEVELOPMENT OF SHOWERS AND THUNDERSTORMS
THURSDAY. SOUTHERLY FLOW AHEAD OF THE FRONT WILL DRAW DEEP
MOISTURE BACK NORTHWARD AFTER CONDITIONS DRIED OUT THE LAST COUPLE
OF DAYS, AS WELL AS PROMPT STORM MOTIONS PARALLEL TO THE BOUNDARY
AND MORE LIKELY TO LEAD TO REPEATED ROUNDS OF RAINFALL. A MODERATE
RISK OF EXCESSIVE RAINFALL (LEVEL 3/4) HAS BEEN ISSUED FOR
SOUTHERN VERMONT AND ADJACENT UPSTATE NEW YORK WHERE ADDITIONAL
HEAVY RAINFALL WILL POSE A RAPID INCREASE IN THE RISK FOR FLASH
FLOODING FOLLOWING THE INTENSE RAINFALL AND FLOODING EARLIER THIS
WEEK. A SEPARATE SLIGHT RISK (LEVEL 2/4) IS IN EFFECT FOR THE
UPPER OHIO VALLEY WHERE ANOTHER FOCUSED AREA OF HEAVY RAINFALL IS
EXPECTED. STRONG FLOW ALOFT AS WELL AS MODERATE INSTABILITY WILL
ALSO LEAD TO A FEW ROBUST, ORGANIZED THUNDERSTORMS CAPABLE OF
LARGE HAIL, DAMAGING WINDS, AND A COUPLE OF TORNADOES FOR THE
INTERIOR NORTHEAST/UPPER OHIO VALLEY. A SLIGHT RISK OF SEVERE
WEATHER (LEVEL 2/5) HAS BEEN ISSUED BY THE STORM PREDICTION CENTER
FOR THE REGION. THE HEAVY RAIN THREAT WILL SHIFT SLIGHTLY
SOUTHEASTWARD FRIDAY AHEAD OF THE THE SLOW-MOVING COLD FRONT WITH
A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHERN NEW ENGLAND AND
THE COASTAL MID-ATLANTIC.
A COMPLEX SUMMER-TIME PATTERN CONTINUES TO UNFOLD ACROSS PORTIONS
OF THE MISSISSIPPI VALLEY/PLAINS, WITH MULTIPLE FOCUS AREAS OF
HEAVY RAIN AND SEVERE WEATHER EXPECTED. MODERATELY STRONG
NORTHWESTERLY FLOW CONTAINING EMBEDDED SHORTWAVES ATOP A
QUASI-STATIONARY FRONTAL BOUNDARY AS WELL AS LINGERING CONVECTIVE
OUTFLOWS WILL CONTINUE TO TRIGGER MULTIPLE FOCUSED CORRIDORS OF
SHOWERS AND THUNDERSTORMS. HIGH MOISTURE TO THE SOUTH AND POOLING
ALONG THE BOUNDARY WILL HELP PROMOTE VERY HEAVY DOWNPOURS WITH
INTENSE RAINFALL RATES AND THE RISK OF FLASH FLOODING. THE
TENDENCY FOR STORMS TO GROW UPSCALE INTO ORGANIZED CONVECTIVE
SYSTEMS WILL INCREASE THE AREAL COVERAGE OF RAINFALL AND HEAVY
RAIN TOTALS. ON THURSDAY, AN ONGOING CONVECTIVE SYSTEM AS WELL AS
ADDITIONAL DEVELOPMENT DURING THE DAY HAS PROMPTED A MODERATE RISK
OF EXCESSIVE RAINFALL OVER CENTRAL MISSISSIPPI WHERE SIGNIFICANT
RAIN TOTALS OVER SEVERAL INCHES ARE POSSIBLE. A SLIGHT RISK IS IN
PLACE MORE BROADLY ACROSS THE LOWER MISSISSIPPI VALLEY TO THE
CENTRAL GULF COAST. ADDITIONAL STORMS, POTENTIALLY AN ORGANIZED
CONVECTIVE SYSTEM, ARE EXPECTED FRIDAY ALONG AND AHEAD OF THE
BOUNDARY FROM THE CENTRAL PLAINS SOUTHEAST INTO THE LOWER
MISSISSIPPI VALLEY WITH A SLIGHT RISK IN EFFECT. FURTHER WEST,
MORE ISOLATED, SCATTERED STORMS ARE EXPECTED, BUT POOLING MOISTURE
AND UPSLOPE FLOW ALONG THE FOOTHILLS OF THE ROCKIES WILL PROVIDE
INSTABILITY FOR ROBUST THUNDERSTORM DEVELOPMENT. A SLIGHT RISK OF
SEVERE WEATHER HAS BEEN ISSUED FOR PORTIONS OF THE
CENTRAL/SOUTHERN HIGH PLAINS THURSDAY FOR THE RISK OF LARGE HAIL
AND SOME DAMAGING WINDS. A FOCUSED CORRIDOR OF THUNDERSTORMS, AND
PERHAPS A CONVECTIVE SYSTEM, IS FORECAST AHEAD OF THE FRONT ON
FRIDAY THROUGH SOUTHERN KANSAS AND NORTHERN OKLAHOMA, WITH YET
ANOTHER SLIGHT RISK OF SEVERE WEATHER.
MEANWHILE, A STAGNANT UPPER-LEVEL HIGH IN PLACE OVER THE
SOUTHWEST/NORTHERN MEXICO THAT HAS LED TO HOT TEMPERATURES OVER
PORTIONS OF THE SOUTHWEST AND SOUTH-CENTRAL U.S. THIS WEEK WILL
CONTINUE TO BUILD IN COVERAGE, PARTICULARLY TO THE NORTHWEST OVER
THE GREAT BASIN/CALIFORNIA/PACIFIC NORTHWEST. WIDESPREAD
HEAT-RELATED ADVISORIES AND WARNINGS ARE IN PLACE ACROSS THE
CENTRAL/SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY AS WELL AS
PORTIONS OF THE DESERT SOUTHWEST AS A SIGNIFICANT HEATWAVE
INTENSIFIES ACROSS THE SOUTHERN TIER OF THE COUNTRY. FORECAST
HIGHS WILL BE IN THE UPPER 90S AND LOW 100S FOR LOCATIONS IN THE
EASTERN HALF OF THE PLAINS AND THE LOWER MISSISSIPPI VALLEY WHICH,
WHEN COMBINED WITH VERY HIGH HUMIDITY, WILL LEAD TO OPPRESSIVE
HEAT INDICES IN THE 110-115 DEGREE RANGE. A FRONTAL BOUNDARY AND
CONVECTIVE OUTFLOWS SLIDING INTO NORTHERN PORTIONS OF THE SOUTHERN
PLAINS/LOWER MISSISSIPPI VALLEY WILL LIKELY BRING A BIT OF RELIEF
FRIDAY. TO THE WEST, WHILE THERE WILL BE LESS HUMIDITY, AIR
TEMPERATURES WILL SOAR MUCH HIGHER INTO THE MID 100S FOR WEST
TEXAS AND NEW MEXICO AND INTO THE 110S FOR THE DESERT SOUTHWEST. A
FEW RECORD-TYING/BREAKING TEMPERATURES ARE POSSIBLE. THE HEAT WILL
BEGIN TO BUILD NORTHWARD INTO CALIFORNIA, THE GREAT BASIN, AND THE
PACIFIC NORTHWEST ON FRIDAY, WITH HIGHS INTO THE 90S AND LOW 100S.
HEAT ADVISORIES ALSO REMAIN IN EFFECT FOR SOUTH FLORIDA WHERE
RELATIVELY WARM TEMPERATURES IN THE MID-90S AND HEAT INDICES UP TO
110 CONTINUE. IN ADDITION TO THE OPPRESSIVE HEAT DURING THE DAY,
OVERNIGHT LOWS WILL REMAIN ABNORMALLY WARM, BRINGING LITTLE RELIEF
FROM THE HEAT OVERNIGHT. NUMEROUS NEAR RECORD-TYING/BREAKING WARM
LOWS ARE EXPECTED. UNFORTUNATELY, THE LONG TERM OUTLOOK THROUGH
THE WEEKEND AND INTO NEXT WEEK IS FOR AN INCREASINGLY SIGNIFICANT
AND OPPRESSIVE HEAT WAVE.
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