753
FXUS01 KWBC 210734
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
333 AM EDT MON AUG 21 2023
VALID 12Z MON AUG 21 2023 - 12Z WED AUG 23 2023
...HEAVY RAIN, SCATTERED FLASH FLOODING, AND GUSTY WINDS
ASSOCIATED WITH HILARY CONTINUE THROUGHOUT THE INTERMOUNTAIN WEST
TODAY...
...EXCESSIVE RAINFALL THREAT EXISTS ACROSS SOUTH TEXAS ON
TUESDAY...
...ABOUT 80 MILLION PEOPLE UNDER HEAT ALERTS AS RECORD-BREAKING
HEAT CONTINUES FROM THE MIDWEST TO GULF COAST...
AFTER MOVING INLAND ACROSS SOUTHERN CALIFORNIA LATE SUNDAY,
MOISTURE ASSOCIATED WITH HILARY IS FORECAST TO CONTINUE STREAMING
NORTHWARD THROUGH THE INTERMOUNTAIN WEST TODAY. THE ANOMALOUS
MOISTURE FETCH IS BEING AIDED BY UPPER-LEVEL TROUGHING ACROSS THE
WEST COAST AND A STRONG RIDGE IN THE MIDDLE OF THE COUNTRY. AREAS
OF LINGERING SHOWERS AND THUNDERSTORMS MAY LEAD TO ADDITIONAL
AREAS OF FLASH FLOODING ACROSS THE HIGH TERRAIN OF THE SIERRA AND
THROUGHOUT MUCH OF NEVADA. FARTHER NORTH, WIDESPREAD MODERATE TO
LOCALLY HEAVY RAIN MAY ALSO CREATE FLOODING CONCERNS THROUGHOUT
THE NORTHERN GREAT BASIN AS A NEARBY FRONTAL BOUNDARY PROVIDES A
FOCUS FOR PRECIPITATION. A SLIGHT RISK (LEVEL 2/4) OF EXCESSIVE
RAINFALL REMAINS IN EFFECT ACROSS A BROAD REGION EXTENDING FROM
NORTHWEST MONTANA TO SOUTHERN NEVADA AND NORTH-CENTRAL ARIZONA.
ADDITIONALLY, GUSTY WINDS ASSOCIATED WITH A SURFACE LOW
PROGRESSING NORTHWARD COULD LEAD TO WIND GUSTS UP TO 70 MPH ACROSS
THE HIGHER TERRAIN, PASSES, AND SUMMITS OF THE INTERMOUNTAIN WEST.
HIGH WIND WARNINGS EXTEND FROM THE DESERT SOUTHWEST TO SOUTHERN
IDAHO. ADDITIONAL MOISTURE FUNNELING NORTHWARD THROUGH MIDWEEK
COULD LEAD TO RENEWED SCATTERED FLASH FLOODING CONCERNS ACROSS THE
NORTHERN GREAT BASIN AND UTAH.
HEAVY RAIN CHANCES ALSO EXIST ACROSS SOUTH TEXAS ON TUESDAY AS A
FAST MOVING TROPICAL DISTURBANCE ENTERS THE REGION FROM THE GULF
OF MEXICO, WHICH THE NATIONAL HURRICANE CENTER HAPPENS TO BE
MONITORING FOR POTENTIAL DEVELOPMENT. REGARDLESS OF ORGANIZATION,
A FEW INCHES OF RAIN WITHIN A SHORT PERIOD OF TIME COULD LEAD TO
SCATTERED FLASH FLOODING THROUGHOUT THE REGION. THIS HAS PROMPTED
A SLIGHT RISK OF EXCESSIVE RAINFALL TO BE ISSUED FROM CORPUS
CHRISTI TO THE U.S.-MEXICO BORDER.
MEANWHILE, THE MORE WIDESPREAD WEATHER HAZARD EXTENDING THROUGH
MIDWEEK INVOLVES SEARING TEMPERATURES IMPACTING A MAJORITY OF THE
CENTRAL U.S. AND GULF COAST. DANGEROUS HEAT UNDERNEATH AN
EXTREMELY POTENT UPPER-LEVEL RIDGE CENTERED OVER THE MIDDLE
MISSISSIPPI VALLEY IS FORECAST TO STRETCH FROM PARTS OF THE UPPER
MIDWEST TO THE GULF COAST. HIGHS INTO THE UPPER-90S AND TRIPLE
DIGITS WILL BE EASY TO COME BY OVER THE NEXT SEVERAL DAYS, WITH
HEAT INDICES INTO THE 110S WHEN TAKING INTO ACCOUNT THE HUMIDITY.
ALTHOUGH THE MIDDLE TO END OF AUGUST CAN BE NOTORIOUSLY HOT, THE
FORECAST TEMPERATURE READINGS FOR THESE AREAS ARE EXPECTED TO
BREAK NUMEROUS DAILY AND POTENTIALLY MONTHLY RECORDS. HIGHS OVER
IOWA AND NEIGHBORING STATES COULD REACH AS HIGH AS 20 DEGREES
ABOVE AVERAGE WHEN COMPARED TO CLIMATOLOGY. THE PROLONGED NATURE
OF THE HEAT WAVE COMBINED WITH VERY WARM OVERNIGHT TEMPERATURES
WILL LIMIT RELIEF FROM THE OPPRESSIVE DAYTIME HEAT AND COMPOUND
OVERALL HEAT IMPACTS. RESIDENTS AND VISITORS ARE ADVISED TO FOLLOW
PROPER HEAT SAFETY, WHICH INCLUDES STAYING HYDRATED AND AVOID
EXTENDED PERIODS OF TIME OUTDOORS. EXCESSIVE HEAT WARNINGS/WATCHES
AND HEAT ADVISORIES CURRENTLY INCLUDE 18 STATES FROM LOUISIANA TO
MINNESOTA, WHICH INCLUDES APPROXIMATELY 80 MILLION PEOPLE. STEAMY
TEMPERATURES INTO THE SOUTHEAST AND MID-ATLANTIC ARE ALSO
FORECAST, WITH TEMPERATURES IN THE MID-ATLANTIC QUICKLY COOLING
BEHIND A COLD FRONT ON TUESDAY.
ELSEWHERE, ON THE PERIPHERY OF THE STRONG UPPER-LEVEL RIDGE,
ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS THE UPPER
MIDWEST AND GREAT LAKES THROUGH TUESDAY. FOR THE PACIFIC
NORTHWEST, DENSE WILDFIRE SMOKE OVER THE REGION IS EXPECTED TO
LINGER FOR AT LEAST AN ADDITIONAL DAY, PROMPTING WIDESPREAD AIR
QUALITY ALERTS.
SNELL
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