616
FXUS01 KWBC 201959
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
358 PM EDT SUN AUG 20 2023
VALID 00Z MON AUG 21 2023 - 00Z WED AUG 23 2023
...THERE IS A SLIGHT TO HIGH RISK OF EXCESSIVE RAINFALL OVER PARTS
OF SOUTHERN CALIFORNIA, THE GREAT BASIN, AND THE NORTHERN
INTERMOUNTAIN REGION...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
SOUTHEASTERN CALIFORNIA...
...THERE ARE AIR QUALITY WARNINGS OVER THE PARTS OF THE PACIFIC
NORTHWEST AND NORTHERN/CENTRAL ROCKIES...
...EXCESSIVE HEAT WARNINGS AND ADVISORIES FROM PARTS OF THE
PLAINS, THE MISSISSIPPI VALLEY, AND CENTRAL/WESTERN GULF COAST...
T.S. HILARY IS FORECAST TO MOVE NORTHWARD OVER BAJA CALIFORNIA
PENINSULA ON SUNDAY AFTERNOON AND INTO SOUTHERN CALIFORNIA BY LATE
AFTERNOON SUNDAY. HILARY IS THEN FORECAST TO CONTINUE TO MOVE
NORTHWARD AND DISSIPATE OVER CENTRAL NEVADA ON MONDAY. HILARY WILL
ALSO PRODUCE POTENTIALLY HISTORIC RAINFALL AMOUNTS EXPECTED TO
CAUSE FLASH, URBAN, AND STEEP-SIDED GULLY FLOODING, INCLUDING
LANDSLIDES, MUDSLIDES, AND DEBRIS FLOWS. LOCALIZED FLOODING
IMPACTS, SOME SIGNIFICANT, ARE ALSO EXPECTED ACROSS NORTHERN
PORTIONS OF THE INTERMOUNTAIN WEST. THEREFORE, THE WPC HAS ISSUED
A HIGH RISK OF EXCESSIVE RAINFALL OVER PARTS OF SOUTHERN/CENTRAL
CALIFORNIA INTO MONDAY MORNING. SEVERE, WIDESPREAD FLASH FLOODING
IS EXPECTED. AREAS THAT NORMALLY DO NOT EXPERIENCE FLASH FLOODING
WILL FLOOD. LIVES AND PROPERTY ARE IN GREAT DANGER THROUGH MONDAY.
HILARY WILL ALSO PRODUCE SHOWERS AND SEVERE THUNDERSTORMS OVER
SOUTHEASTERN CALIFORNIA. THEREFORE, THE SPC HAS ISSUED A SLIGHT
RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTHEASTERN CALIFORNIA
THROUGH MONDAY MORNING.
THE HAZARDS ASSOCIATED WITH THESE THUNDERSTORMS ARE LIGHTNING,
SEVERE THUNDERSTORM WIND GUSTS, A FEW TORNADOES, AND A MINIMAL
THREAT OF HAIL. THE SHOWERS AND THUNDERSTORMS WILL EXTEND
NORTHWARD INTO THE NORTHERN INTERMOUNTAIN REGION, NORTHERN
ROCKIES, AND NORTHERN PLAINS THROUGH MONDAY AFTERNOON.
THE THREAT OF EXCESSIVE RAINFALL CONTINUES ON MONDAY. THEREFORE,
THE WPC HAS ISSUED A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS
OF CALIFORNIA, GREAT BASIN, SOUTHWEST, PACIFIC NORTHWEST, NORTHERN
INTERMOUNTAIN REGION, AND NORTHERN ROCKIES FROM MONDAY INTO
TUESDAY MORNING. THE ASSOCIATED HEAVY RAIN WILL CREATE MAINLY
LOCALIZED AREAS OF FLASH FLOODING, WITH URBAN AREAS, ROADS, SMALL
STREAMS, AND BURN SCARS THE MOST VULNERABLE.
IN ADDITION, THE THREAT OF SEVERE THUNDERSTORMS DECREASES SLIGHTLY
ON MONDAY. ON MONDAY, THE ASSOCIATED MOISTURE PLUME MOVES EASTWARD
INTO THE SOUTHWEST AND GREAT BASIN, PRODUCING STRONG TO SEVERE
THUNDERSTORMS. THEREFORE, THE SPC HAS ISSUED A MARGINAL RISK OF
SEVERE THUNDERSTORMS OVER PARTS OF THE SOUTHWEST, GREAT BASIN, AND
NORTHERN ROCKIES FROM MONDAY INTO TUESDAY MORNING. THE HAZARDS
ASSOCIATED WITH THESE THUNDERSTORMS ARE FREQUENT LIGHTNING, SEVERE
THUNDERSTORM WIND GUSTS, HAIL, AND A MINIMAL THREAT OF TORNADOES.
THE THREAT OF EXCESSIVE RAINFALL CONTINUES ON TUESDAY AS THE
SHOWERS AND THUNDERSTORMS WITH HEAVY RAIN OVER PARTS OF THE GREAT
BASIN, SOUTHWEST, AND NORTHERN INTERMOUNTAIN REGION. THEREFORE,
THE WPC HAS ISSUED A SLIGHT RISK OF EXCESSIVE RAINFALL WITH THESE
THUNDERSTORMS OVER TWO REGIONS, THE FIRST AREA OVER PARTS OF THE
NORTHERN INTERMOUNTAIN REGION AND THE SECOND OVER PARTS OF THE
GREAT BASIN ON TUESDAY. THE ASSOCIATED HEAVY RAIN WILL CREATE
MAINLY LOCALIZED AREAS OF FLASH FLOODING, WITH URBAN AREAS, ROADS,
SMALL STREAMS, AND BURN SCARS THE MOST VULNERABLE. IN ADDITION, ON
TUESDAY, THE THREAT OF SEVERE THUNDERSTORMS ENDS OVER THE WEST.
FURTHERMORE, WILDFIRE SMOKE OVER PARTS OF THE PACIFIC NORTHWEST
AND NORTHERN/CENTRAL ROCKIES HAS PROMPTED AIR QUALITY ALERTS OVER
PARTS OF THE PACIFIC NORTHWEST AND NORTHERN/CENTRAL ROCKIES.
MEANWHILE, A FRONT OVER THE GREAT LAKES WILL MOVE INTO THE
NORTHEAST AND SETTLE OVER THE MID-ATLANTIC PARTS BY TUESDAY. THE
SYSTEM WILL PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS OVER PARTS
OF THE NORTHEAST ON MONDAY INTO MONDAY EVENING.
IN ADDITION, UPPER-LEVEL ENERGY AND TROPICAL MOISTURE WILL MOVE
ACROSS THE CENTRAL GULF COAST SUNDAY EVENING AND MONDAY. THE
ENERGY WILL PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS OVER PARTS
OF THE REGION. FURTHER, ONSHORE FLOW OFF THE ATLANTIC WILL
CONTINUE TO PRODUCE SHOWERS AND THUNDERSTORMS OVER THE SOUTHERN
TIP OF FLORIDA THROUGH TUESDAY.
AS THE ENERGY AND TROPICAL MOISTURE MOVES OVER THE WESTERN GULF
COAST, THE SYSTEM WILL PRODUCE SHOWERS AND THUNDERSTORMS WITH
HEAVY RAIN OVER PARTS OF SOUTH-CENTRAL TEXAS. THEREFORE, THE WPC
HAS ISSUED A SLIGHT RISK OF EXCESSIVE RAINFALL WITH THESE
THUNDERSTORMS OVER PARTS OF SOUTH-CENTRAL TEXAS ON TUESDAY. THE
ASSOCIATED HEAVY RAIN WILL CREATE MAINLY LOCALIZED AREAS OF FLASH
FLOODING, WITH URBAN AREAS, ROADS, AND SMALL STREAMS THE MOST
VULNERABLE.
FURTHERMORE, AN UPPER-LEVEL HIGH OVER THE CENTRAL PLAINS/MIDDLE
MISSISSIPPI VALLEY WILL CREATE OPPRESSIVE DAYTIME HEAT, LIMITED
OVERNIGHT COOLING, WHICH WILL ALSO CONTRIBUTE TO THE EFFECTS OF
HEAT, PROMPTING EXCESSIVE HEAT WARNINGS AND HEAT ADVISORIES OVER
PORTIONS OF THE CENTRAL/SOUTHERN PLAINS, THE UPPER/MIDDLE/LOWER
MISSISSIPPI VALLEY, CENTRAL/WESTERN GULF COAST.
IN ADDITION, DANGEROUS HEAT WILL CONTINUE TO INTENSIFY AND EXPAND
INTO THE PLAINS STATES, WITH NUMEROUS DAILY HIGH-TEMPERATURE
RECORDS EXPECTED, ESPECIALLY IN THE CENTRAL PLAINS AND TEXAS. THE
HEAT WAVE WILL THEN EXPAND EARLY NEXT WEEK TO INCLUDE MUCH OF THE
CENTRAL AND SOUTHEAST U.S. SOME LOCATIONS IN THE MIDWEST MAY SEE
THEIR HOTTEST DAY OF THE YEAR SO FAR THIS WEEKEND. PORTIONS OF THE
SOUTH CENTRAL U.S. AND GULF COAST MAY FURTHER EXTEND THEIR RECORD
NUMBER OF DAYS WITH A HEAT INDEX READING OF AT LEAST 110ĀF.
MOREOVER, THE PROLONGED NATURE OF THE HEAT WAVE, COMBINED WITH
VERY WARM OVERNIGHT TEMPERATURES, WILL LIMIT THE RELIEF FROM THE
OPPRESSIVE DAYTIME HEAT AND COMPOUND OVERALL HEAT IMPACTS.
FURTHER, EXCESSIVE HEAT IS ANTICIPATED TO FOCUS OVER THE
SOUTHEASTERN QUADRANT OF THE COUNTRY NEXT WEEK. THE GREATEST RISK
OF EXCESSIVE HEAT IS FOR EASTERN TEXAS AND PARTS OF THE GULF COAST
STATES.
ZIEGENFELDER
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