322
FXUS21 KWNC 251925
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 25 2023
SYNOPSIS: UNSETTLED WEATHER LOOKS LIKELY TO IMPACT THE SOUTHERN TIER OF THE
CONTIGUOUS U.S. (CONUS) AS WE ENTER THE FIRST WEEK OF 2024. IN CALIFORNIA, MEAN
MID-LEVEL LOW PRESSURE IS LIKELY TO CONTINUE TO BRING CHANCES FOR HEAVY
PRECIPITATION TO MUCH OF THE STATE WITH LINGERING PRECIPITATION EARLY IN THE
PERIOD ACROSS SOUTHERN CALIFORNIA BEFORE A POTENTIAL RESURGENCE FURTHER NORTH
AS THE PERIOD PROGRESSES. MEANWHILE, IN THE LOWER-MISSISSIPPI VALLEY AND
SOUTHERN PLAINS HEAVY PRECIPITATION MAY DEVELOP ASSOCIATED WITH AN AREA OF LOW
PRESSURE MOVING ACROSS THE SOUTHERN TIER.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF CALIFORNIA, TUE-MON, JAN 2-8.
SLIGHT RISK OF HEAVY SNOW FOR THE SIERRA NEVADA, SOUTHERN CASCADES, AND COASTAL
RANGES OF NORTHERN CALIFORNIA, THU-MON, JAN 4-8.
SLIGHT RISK OF HIGH WINDS FOR COASTAL CENTRAL AND NORTHERN CALIFORNIA AND
SOUTHWESTERN OREGON, THU-MON, JAN 4-8.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE EASTERN SOUTHERN PLAINS AND
LOWER-MISSISSIPPI VALLEY, TUE-THU, JAN 2-4.
DETAILED SUMMARY
FOR THURSDAY DECEMBER 28 - MONDAY JANUARY 01:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY JANUARY 02 - MONDAY JANUARY 08: DURING THE WEEK-2 PERIOD, WEAK
HEIGHT ANOMALIES ARE FORECAST ACROSS THE COUNTRY WITH A TRANSIENT PATTERN
SETTING UP. IN GENERAL, SLIGHTLY NEGATIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST
ACROSS THE WESTERN CONUS AND SOUTHEAST. WITH NEAR-NORMAL 500-HPA HEIGHTS
FAVORED IN THE NORTHEAST AND MIDWEST AND POSITIVE 500-HPA HEIGHTS FAVORED IN
ALASKA.
CALIFORNIA REMAINS THE FOCUS FOR POTENTIAL HAZARDS DURING THE FIRST WEEK OF
JANUARY BUT WITH INCREASED UNCERTAINTY RELATIVE TO PREVIOUS FORECASTS. THE
PROBABILISTIC EXTREMES TOOLS (PETS) FROM THE GEFS AND ECMWF CONTINUE TO
INDICATE AT LEAST A 20% CHANCE FOR THREE DAY PRECIPITATION TOTALS TO EXCEED THE
85TH CLIMATOLOGICAL PERCENTILE AND 1 INCH ACROSS PARTS OF CENTRAL AND SOUTHERN
CALIFORNIA EARLY IN THE PERIOD WHILE RAW TOOLS HAVE HAD LESS RUN TO RUN
CONSISTENCY FOR PRECIPITATION ACROSS CALIFORNIA EARLY IN THE PERIOD. AS THE
PERIOD PROGRESSES, A MID-LEVEL TROUGH RELOADS OFF THE WEST COAST BRINGING
INCREASED CHANCES FOR HEAVY PRECIPITATION BACK INTO CENTRAL AND NORTHERN
CALIFORNIA BY THE MIDDLE AND END OF WEEK-2. THIS SECOND WAVE OF PRECIPITATION
HAS MORE SUPPORT AND CONSISTENCY FROM RAW MODEL TOOLS. THEREFORE, A SLIGHT RISK
OF HEAVY PRECIPITATION IS POSTED FOR MUCH OF CALIFORNIA FOR THE ENTIRE WEEK-2
PERIOD. A SLIGHT RISK OF HEAVY SNOW IS POSTED FOR HIGHER ELEVATIONS OF THE
SIERRA NEVADA, SOUTHERN CASCADES, AND COASTAL RANGES OF NORTHERN CALIFORNIA FOR
JAN 4-8 AS THE TROUGH RELOADS AND BRINGS HIGHER CHANCES OF PRECIPITATION TO
AREAS FURTHER NORTH IN CALIFORNIA. ASSOCIATED WITH THIS TROUGH AN INCREASE IN
CHANCES FOR HIGH WINDS IS FORECAST ALONG THE CENTRAL AND NORTHERN CALIFORNIA
COAST INTO SOUTHWESTERN OREGON. AN ASSOCIATED SLIGHT RISK OF HIGH WINDS IS
POSTED FOR JAN 4-8.
FURTHER EAST, ACROSS THE LOWER-MISSISSIPPI VALLEY AND SOUTHERN PLAINS, A
SHORTWAVE TROUGH IS EXPECTED TO EJECT OUT OF THE ROCKY MOUNTAINS EARLY IN THE
PERIOD. BOTH THE GEFS AND ECMWF PETS FORECAST AT LEAST A 20% CHANCE OF THREE
DAY PRECIPITATION EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND AN INCH OF
PRECIPITATION. WHILE THE ECMWF PET HAS A GREATER THAN 40% CHANCE INTO WESTERN
TEXAS OF EXCEEDING THE 85TH PERCENTILE, TOTAL PRECIPITATION AMOUNTS ARE
UNLIKELY TO REACH HAZARDOUS THRESHOLDS. TEMPERATURES ARE FORECAST TO REMAIN
ABOVE FREEZING LIMITING CHANCES FOR HEAVY SNOW. THEREFORE, A SLIGHT RISK OF
HEAVY PRECIPITATION IS POSTED FOR JAN 2-4 FOR PARTS OF THE EASTERN SOUTHERN
PLAINS AND LOWER-MISSISSIPPI VALLEY. THIS SYSTEM MAY CONTINUE TO PROPAGATE
EASTWARD THROUGH THE WEEK-2 PERIOD WITH RAW TOOLS SHOWING LESS PRECIPITATION
INTO EASTERN PORTIONS OF THE SOUTHEAST. ONCE THE STORM REACHES THE EAST COAST
IT MAY FOLLOW THE COAST NORTHEAST. THE GEFS AND ECMWF FORECAST THIS STORM TO
STAY OFFSHORE OF THE EAST COAST BUT LIKELY BEARS WATCHING IF THE SYSTEM WERE TO
REMAIN CLOSER TO SHORE.
IN FLORIDA AND SOUTHEAST, THE GEFS PET CONTINUES TO INDICATE CHANCES FOR
TEMPERATURES TO FALL BELOW THE 15TH CLIMATOLOGICAL PERCENTILE AND 40 DEG F.
HOWEVER, THE ECMWF PET HAS REDUCED CHANCES RELATIVE TO PRIOR FORECASTS AND THIS
AREA WOULD ALSO LIKELY HAVE FALLEN BELOW THESE TEMPERATURES PRIOR TO THE
FORECAST PERIOD BY THIS TIME. THEREFORE, NO CORRESPONDING TEMPERATURE HAZARD IS
POSTED TODAY.
IN ALASKA, PRECIPITATION IS FORECAST TO CONTINUE ACROSS MUCH OF SOUTHEAST AND
SOUTH-CENTRAL ALASKA DURING THE WEEK-2 PERIOD. HOWEVER, THERE ARE ONLY
SCATTERED AREAS WHERE 3-DAY PRECIPITATION TOTALS ARE FORECAST TO REACH 2 INCHES
IN THE PETS AND RAW TOOLS. THEREFORE, NO PRECIPITATION HAZARDS ARE POSTED. AN
AREA OF LOW-PRESSURE IS FORECAST TO BRING STRONG MARITIME WINDS TO AREAS AROUND
THE ALEUTIAN ISLANDS AND ALASKA PENINSULA BUT ONSHORE WINDS ARE UNLIKELY TO
REACH HAZARDOUS THRESHOLDS.
FORECASTER: RYAN BOLT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page