637
FXUS21 KWNC 061945
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 06 2025
SYNOPSIS: ONGOING COLD IN THE EAST MAY CONTINUE INTO EARLY WEEK-2 AS A
REINFORCING MID-LEVEL TROUGH MAY MOVE INTO THE EASTERN CONTIGUOUS U.S. (CONUS)
LEADING TO SLIGHT CHANCES FOR MUCH BELOW NORMAL TEMPERATURES AND LINGERING LAKE
EFFECT SNOW. HIGH WINDS ACROSS PORTIONS OF THE PLAINS AND INTERIOR MOUNTAIN
WEST ARE POSSIBLE THROUGH MUCH OF WEEK-2. SANTA ANA WINDS WILL REMAIN POSSIBLE
INTO EARLY WEEK-2 ACROSS PARTS OF SOUTHERN CALIFORNIA. IN ALASKA, THERE
CONTINUE TO BE CHANCES FOR HEAVY PRECIPITATION, HIGH ELEVATION SNOW, AND
PERIODS OF HIGH WINDS EARLY IN THE PERIOD.
HAZARDS
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE OHIO,
TENNESSEE, MIDDLE AND LOWER MISSISSIPPI VALLEYS, SOUTHEAST, AND MID-ATLANTIC,
TUE-THU, JAN 14-16.
SLIGHT RISK OF HEAVY SNOW FOR DOWNWIND PORTIONS OF LAKES ERIE AND ONTARIO,
TUE-THU, JAN 14-16.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR PORTIONS OF SOUTHERN CALIFORNIA,
TUE-THU, JAN 14-16.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR PORTIONS OF THE NORTHERN AND CENTRAL
PLAINS, TUE-SAT, JAN 14-18.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR MUCH OF THE INTERIOR MOUNTAIN WEST,
THU-MON, JAN 16-20.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR WESTERN MAINLAND ALASKA, TUE-THU, JAN
14-16.
DETAILED SUMMARY
FOR THURSDAY JANUARY 09 - MONDAY JANUARY 13:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY JANUARY 14 - MONDAY JANUARY 20: THERE IS INCREASED UNCERTAINTY IN
THE MID-LEVEL HEIGHT PATTERN AS WE MOVE THROUGH THE MIDDLE OF JANUARY ACROSS
THE CONTIGUOUS U.S. (CONUS). THE ARCTIC OSCILLATION FORECAST FOR THE WEEK-2
PERIOD IS NEAR-NORMAL BUT WITH A LARGE SPREAD, BOTH POSITIVE AND NEGATIVE
ANOMALIES. THERE ARE ALSO DIFFERENCES IN THE EXPLICIT HEIGHT PATTERN ACROSS THE
CONUS BY THE MIDDLE OF THE PERIOD BETWEEN THE GEFS AND ECENS. HOWEVER, IN THE
EAST, GENERALLY NEGATIVE 500-HPA HEIGHT ANOMALIES AND ASSOCIATED TROUGHING ARE
FORECAST ACROSS THE EAST COAST INTO THE WESTERN ATLANTIC, THE ECENS MAINTAINS A
DEEPER TROUGH ACROSS THE EASTERN CONUS RELATIVE TO THE GEFS. IN THE WEST,
MID-LEVEL RIDGING GIVES WAY TO MID-LEVEL TROUGHING BY THE MIDDLE TO END OF THE
PERIOD. AND OVER ALASKA, A MID-LEVEL TROUGH AT THE END OF WEEK-1 INTO EARLY
WEEK-2 EVOLVES INTO A MID-LEVEL RIDGE BY THE MIDDLE OF WEEK-2.
A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES REMAINS FORECAST FOR THE FIRST
THREE DAYS OF WEEK-2, JAN 14-16, ACROSS THE SOUTHEASTERN CONUS. THIS PERIOD IS
WHEN THE GEFS AND ECENS ARE IN THE BEST AGREEMENT RELATIVE TO THE POSITION OF
THE MID-LEVEL TROUGH THAT IS LIKELY TO FORCE THESE MINIMUM TEMPERATURES. THE
PROBABILISTIC EXTREMES TOOLS (PETS) FORECAST 20-40 PERCENT CHANCES FOR
TEMPERATURES TO FALL BELOW THE 15TH CLIMATOLOGICAL PERCENTILE ACROSS THESE
REGIONS. WHILE ABSOLUTE TEMPERATURES ARE UNLIKELY TO REACH HAZARDOUS THRESHOLDS
THE POTENTIAL FOR SOME ENHANCED WIND MAY BRING WINDCHILLS INTO STRIKING
DISTANCE OF THRESHOLDS.
ASSOCIATED WITH THE MID-LEVEL TROUGH AND COLD AIR ADVECTION IS A SLIGHT RISK OF
HEAVY SNOW FOR DOWNWIND PORTIONS OF LAKES ERIE AND ONTARIO DUE TO ENHANCED
CHANCES FOR LAKE EFFECT SNOW, JAN 14-16. THE EASTERN GREAT LAKES SURFACE
TEMPERATURES ARE LIKELY TO CONTINUE TO DECLINE IN THE NEXT COUPLE WEEKS WITH
BELOW-NORMAL TEMPERATURES FORECAST AND THIS MAY LEAD TO REDUCED STRENGTH IN THE
POTENTIAL FOR LAKE EFFECT. NEVERTHELESS, THE RISK PERSISTS INTO EARLY WEEK-2.
ALONG OR JUST OFFSHORE OF SOUTHERN CALIFORNIA, AN INVERTED TROUGH MAY DEVELOP
AND SURFACE HIGH PRESSURE IS FORECAST ACROSS THE GREAT BASIN. THIS PATTERN
WOULD BRING INCREASED CHANCES FOR SANTA ANA WINDS TO THE REGION. AS SUCH, A
SLIGHT RISK OF HIGH WINDS IS POSTED JAN 14-16 ACROSS COASTAL AREAS OF SOUTHERN
CALIFORNIA.
IN THE WEST, THE MID-LEVEL RIDGE MAY PROMOTE DOWNSLOPE FLOW ACROSS THE NORTHERN
AND CENTRAL PLAINS EARLY IN THE WEEK-2 PERIOD. AS THE RIDGE SUBSIDES AND
MID-LEVEL TROUGHING DEVELOPS A SECOND FORCING FOR PERIODS OF EPISODIC HIGH
WINDS DEVELOPS ACROSS A BROADER AREA OF THE INTERIOR MOUNTAIN WEST AND INTO THE
PLAINS. THIS IS SUPPORTED BY THE EVOLUTION OF THE WIND PETS FROM THE GEFS AND
ECENS. THERE IS LOCALIZED SUPPORT ACROSS THE PLAINS IN THE ECENS PET FOR WINDS
TO EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE. BY THE MIDDLE OF THE PERIOD,
SUPPORT FROM THE ECENS AND GEFS PETS GROWS ACROSS MUCH OF THE WEST AND INTO THE
PLAINS. BY THE END OF THE PERIOD, THERE IS REDUCED SUPPORT ACROSS PORTIONS OF
THE PLAINS. THEREFORE, TWO AREAS OF HIGH WIND HAZARDS ARE POSTED. THE FIRST IS
ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS FOR JAN 14-18. THE SECOND IS
ACROSS MUCH OF THE INTERIOR MOUNTAIN WEST FOR JAN 16-20.
IN ALASKA, AT THE END OF WEEK-1 AND PERHAPS INTO EARLY WEEK-2, ONSHORE
MID-LEVEL FLOW AND A SURFACE LOW-PRESSURE ARE FORECAST ACROSS SOUTHERN ALASKA.
HOWEVER, MODELS INDICATE THE STRONGEST CHANCES FOR HAZARDOUS HEAVY
PRECIPITATION AND HIGH WINDS TO BE REDUCED BY WEEK-2. AS SUCH, NO WEEK-2
HAZARDS ARE POSTED AT THIS TIME FOR THIS REGION. IN THE WESTERN MAINLAND, MODEL
GUIDANCE IS INDICATING ENHANCED CHANCES FOR HIGH WINDS TO IMPACT THE REGION.
THIS MAY BE ASSOCIATED WITH AN AREA OF LOW-PRESSURE MOVING THROUGH THE BERING
PRIOR TO WEEK-2 AND SETTING UP A STRONG PRESSURE GRADIENT OVER WESTERN ALASKA.
THEREFORE, A SLIGHT RISK OF HIGH WINDS IS POSTED FOR JAN 14-16 FOR THIS REGION.
BY THE END OF WEEK-2, MUCH BELOW NORMAL TEMPERATURE CHANCES ARE BEGINNING TO
INCREASE ACROSS PARTS OF THE NORTHWEST AND NORTHERN PLAINS. WHILE THE SIGNAL
REMAINS RELATIVELY WEAK, THIS AREA WILL CONTINUE TO BE MONITORED FOR THE
POTENTIAL OF ANOTHER ROUND OF ANOMALOUSLY COLD AIR TO INTRUDE INTO THE CONUS BY
THE END OF WEEK-2.
FORECASTER: RYAN BOLT
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