800
FXUS01 KWBC 210722
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
222 AM EST THU DEC 21 2023
VALID 12Z THU DEC 21 2023 - 12Z SAT DEC 23 2023
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PARTS OF
SOUTHERN CALIFORNIA ON THURSDAY...
... THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF
SOUTHERN CALIFORNIA AND THE SOUTHWEST ON FRIDAY...
...LIGHT TO MODERATE SNOW OVER THE CASCADES/NORTHERN INTERMOUNTAIN
REGION/CENTRAL ROCKIES AND SNOW AT THE HIGHER ELEVATIONS OVER
PARTS OF THE SOUTHWEST, GREAT BASIN, AND SOUTHERN ROCKIES ON
FRIDAY...
AN UPPER-LEVEL OFF THE SOUTHERN CALIFORNIA COAST WILL SLOWLY MOVE
SOUTHWARD OVER THE PACIFIC BEFORE MOVING INLAND OVER THE SOUTHWEST
AND NORTHWESTERN MEXICO BY SATURDAY. THE LOW WILL STREAM MOISTURE
INTO SOUTHERN CALIFORNIA, CREATING HEAVY RAIN. THEREFORE, THE WPC
HAS ISSUED A MODERATE RISK OF EXCESSIVE RAINFALL OVER PARTS OF
SOUTHERN CALIFORNIA THROUGH FRIDAY MORNING. THE ASSOCIATED HEAVY
RAIN WILL CREATE NUMEROUS AREAS OF FLASH FLOODING WITH NARROW
CANYONS/GULLIES AND BURN SCARS THE MOST VULNERABLE. FURTHERMORE,
MANY STREAMS MAY FLOOD, POTENTIALLY AFFECTING LARGER RIVERS. IN
ADDITION, THUNDERSTORMS WILL DEVELOP CLOSER TO THE SOUTHERN BORDER.
ON FRIDAY, AS THE UPPER-LEVEL LOW BEGINS TO MOVE ONSHORE, HEAVY
RAIN WILL START TO MOVE INTO THE SOUTHWEST WHILE CONTINUING OVER
PARTS OF SOUTHERN CALIFORNIA. THEREFORE, THE WPC HAS ISSUED A
SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF SOUTHERN
CALIFORNIA AND THE SOUTHWEST FROM FRIDAY INTO SATURDAY MORNING.
THE ASSOCIATED HEAVY RAIN WILL CREATE MAINLY LOCALIZED AREAS OF
FLASH FLOODING, WITH URBAN AREAS, ROADS, SMALL STREAMS, NARROW
CANYONS/GULLIES, AND BURN SCARS THE MOST VULNERABLE.
MEANWHILE, A FRONT OVER THE EASTERN PACIFIC MOVES ONSHORE OVER THE
PACIFIC NORTHWEST ON FRIDAY AND THEN TO THE NORTHERN HIGH PLAINS
BY SATURDAY. THE SYSTEM WILL PRODUCE RAIN AND HIGHER-ELEVATION
SNOW OVER PARTS OF THE NORTHWEST. OVERNIGHT FRIDAY INTO SATURDAY,
SNOW WILL DEVELOP OVER PARTS OF THE NORTHERN INTERMOUNTAIN REGION.
MOREOVER, OVERNIGHT FRIDAY, SNOW WILL DEVELOP OVER PARTS OF THE
HIGHER ELEVATIONS OF THE SOUTHWEST AND CENTRAL/SOUTHERN ROCKIES.
FURTHERMORE, THE CIRCULATION AROUND THE AREA OF HIGH PRESSURE OVER
THE SOUTHEAST/MID-ATLANTIC WILL PRODUCE RETURN FLOW OFF THE GULF
OF MEXICO THAT WILL SLOWLY MOISTEN THE AIR OVER THE
CENTRAL/SOUTHERN PLAINS NORTHWARD TO THE GREAT LAKES. LIGHT RAIN
WILL DEVELOP OVER PARTS OF THE WESTERN GULF COAST AND GRADUALLY
EXPAND NORTHWARD OVER THE CENTRAL/SOUTHERN PLAINS BY THURSDAY
EVENING. OVERNIGHT THURSDAY INTO FRIDAY, THE RAIN WILL MOVE/EXPAND
INTO PARTS OF THE MIDDLE/LOWER MISSISSIPPI VALLEY AND PARTS OF THE
GREAT LAKES. RAIN WILL EXTEND FROM THE GREAT LAKES TO THE CENTRAL
GULF COAST BY SATURDAY.
ZIEGENFELDER
GRAPHICS AVAILABLE AT
HTTPS://WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP
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