767
FXUS21 KWNC 071955
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 07 2025
SYNOPSIS: ONGOING COLD IN THE EAST MAY CONTINUE INTO EARLY WEEK-2 AS A
MID-LEVEL LOW PRESSURE REMAINS FORECAST IN THE EASTERN CONTIGUOUS U.S. (CONUS)
LEADING TO INCREASED CHANCES FOR MUCH BELOW NORMAL TEMPERATURES AND LINGERING
LAKE EFFECT SNOW. ANOTHER MID-LEVEL LOW IS FORECAST TO DEVELOP AND INTRUDE INTO
THE NORTHWEST AND GREAT PLAINS BY THE END OF THE WEEK-2 TRIGGERING THE NEXT
ROUND OF POTENTIAL HAZARDOUS WEATHER. THE ASSOCIATED FRONTAL SYSTEM ENHANCES
THE LIKELIHOOD FOR MULTIPLE HAZARDS INCLUDING HEAVY PRECIPITATION IN THE SOUTH,
SNOW FROM THE CENTRAL ROCKIES INTO THE GREAT LAKES, AND HIGH WINDS ACROSS THE
WESTERN AND CENTRAL CONUS. BEHIND THIS SYSTEM, INCREASED RISK FOR MUCH BELOW
NORMAL TEMPERATURES ARE ANTICIPATED TO RETURN ACROSS PARTS OF THE ROCKIES AND
GREAT PLAINS. IN ADDITION HIGH WINDS ARE POSSIBLE THROUGHOUT THE INTERIOR
MOUNTAIN WEST THROUGH MUCH OF WEEK-2. SANTA ANA WINDS REMAIN POSSIBLE INTO
EARLY WEEK-2 ACROSS PARTS OF SOUTHERN CALIFORNIA. IN ALASKA, HIGH WINDS ARE
POSSIBLE ACROSS THE WESTERN MAINLAND EARLY IN THE PERIOD FOLLOWED BY INCREASED
CHANCES FOR GAP WINDS ACROSS THE SOUTHERN MAINLAND BY THE MIDDLE OF WEEK-2.
HAZARDS
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE
MID-ATLANTIC, CENTRAL AND SOUTHERN APPALACHIANS, THE UPPER OHIO AND UPPER
TENNESSEE VALLEYS, AND SOUTHEAST, WED-THU, JAN 15-16.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE OHIO,
TENNESSEE, MIDDLE AND LOWER MISSISSIPPI VALLEYS, SOUTHEAST, AND MID-ATLANTIC,
WED-SAT, JAN 15-18.
SLIGHT RISK OF HEAVY SNOW FOR DOWNWIND PORTIONS OF LAKES ERIE AND ONTARIO,
WED-FRI, JAN 15-17.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR PORTIONS OF SOUTHERN CALIFORNIA,
WED-FRI, JAN 15-17.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR MUCH OF THE INTERIOR MOUNTAIN WEST,
WED-TUE, JAN 15-21.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE LOWER MISSISSIPPI
VALLEY, SOUTHERN PLAINS, TENNESSEE VALLEY, SAT-MON, JAN 18-20.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE CENTRAL ROCKIES, CENTRAL AND
NORTHERN PLAINS, MIDDLE AND UPPER MISSISSIPPI VALLEY AND WESTERN GREAT LAKES,
SAT-MON, JAN 18-20.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS,
MIDDLE MISSISSIPPI VALLEY, AND GREAT LAKES, SAT-MON, JAN 18-20.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE NORTHWEST,
ROCKIES, AND CENTRAL AND NORTHERN PLAINS, SUN-TUE, JAN 19-21.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR NORTHWESTERN MAINLAND ALASKA,
WED-THU, JAN 15-16.
SLIGHT RISK FOR PERIODS OF GAP WINDS ACROSS PARTS OF SOUTHERN MAINLAND ALASKA,
FRI-MON, JAN 17-20.
DETAILED SUMMARY
FOR FRIDAY JANUARY 10 - TUESDAY JANUARY 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JANUARY 15 - TUESDAY JANUARY 21: THERE IS BETTER AGREEMENT AMONG
THE DYNAMICAL MODELS MID-LEVEL HEIGHT FORECASTS DURING THE WEEK-2 PERIOD
COMPARED TO YESTERDAY. THE PATTERN IS MORE AMPLIFIED TODAY RELATIVE TO
YESTERDAY, PARTICULARLY EARLY IN THE WEEK-2 PERIOD. A STRONG POSITIVE MID-LEVEL
ANOMALY IS FORECAST ACROSS THE WEST WITH ASSOCIATED AMPLIFIED RIDGING. IN THE
EAST, NEGATIVE MID-LEVEL ANOMALIES ARE FORECAST WITH ASSOCIATED DEEP TROUGHING.
THE FORECAST LOCATION OF THE TROUGH AND RIDGE AXIS BETWEEN THE GEFS, ECENS, AND
CANADIAN ENSEMBLES ARE ALL IN RELATIVELY GOOD AGREEMENT. THROUGH THE PERIOD,
THE RIDGING ACROSS THE WEST GIVES WAY TO DEVELOPING MID-LEVEL TROUGHING.
MEANWHILE, AMPLIFIED MID-LEVEL RIDGING DEVELOPS UPSTREAM ACROSS THE NORTHEAST
PACIFIC AND INTO ALASKA. IN THE EAST, THE TROUGH IS PREDICTED TO PROGRESS EAST
INTO THE WESTERN ATLANTIC.
WITH BETTER AGREEMENT AMONG THE MODEL HEIGHT FORECASTS AND THE PROBABILISTIC
EXTREMES TOOLS (PETS), A MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES IS
FORECAST FOR PORTIONS OF THE MID-ATLANTIC, CENTRAL AND SOUTHERN APPALACHIANS,
THE UPPER OHIO AND TENNESSEE VALLEYS, AND SOUTHEAST FOR JAN 15-16. PETS FROM
THE GEFS AND ECENS INDICATE 40-60% CHANCES OF TEMPERATURES FALLING BELOW THE
15TH CLIMATOLOGICAL PERCENTILE DURING THE COLDEST TIME OF THE YEAR,
CLIMATOLOGICALLY, ACROSS THE EASTERN CONTIGUOUS U.S. (CONUS). A BROADER AREA IS
HIGHLIGHTED WITH A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE FIRST
FOUR DAYS OF WEEK-2, JAN 15-18, ACROSS THE SOUTHEASTERN CONUS EXTENDING NORTH
INTO THE OHIO VALLEY AND MID-ATLANTIC. THE PETS IN THE BROADER AREA FORECAST
20-40 PERCENT CHANCES OF MINIMUM TEMPERATURES FALLING BELOW THE 15TH
CLIMATOLOGICAL PERCENTILE ACROSS THESE REGIONS. WHILE ABSOLUTE TEMPERATURES MAY
NOT REACH HAZARDOUS THRESHOLDS, CONSIDERING APPARENT TEMPERATURES, THESE AREAS
MAY FALL BELOW THE NECESSARY THRESHOLDS.
A SLIGHT RISK OF HEAVY SNOW IS POSTED FOR DOWNWIND PORTIONS OF LAKES ERIE AND
ONTARIO DUE TO ENHANCED CHANCES FOR LAKE EFFECT SNOW, JAN 15-17, ASSOCIATED
WITH THE MID-LEVEL TROUGH AND COLD AIR ADVECTION THE EASTERN GREAT LAKES
SURFACE TEMPERATURES ARE LIKELY TO CONTINUE TO DECLINE IN THE NEXT COUPLE WEEKS
WITH BELOW-NORMAL TEMPERATURES FORECAST WHICH MAY LEAD TO DECREASING POTENTIAL
FOR LAKE EFFECT SNOW. DESPITE SOME UNCERTAINTY, THE HEAVY SNOW 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 15-17 ACROSS COASTAL AREAS OF SOUTHERN
CALIFORNIA.
IN THE WEST, THE MID-LEVEL RIDGING MAY PROMOTE DOWNSLOPE FLOW ACROSS THE
NORTHERN AND CENTRAL PLAINS EARLY IN THE WEEK-2 PERIOD. AS THE RIDGE
DE-AMPLIFIES AND MID-LEVEL TROUGHING DEVELOPS, A SECOND FORCING FOR PERIODS OF
EPISODIC HIGH WINDS IS FORECAST TO DEVELOP ACROSS A BROADER AREA OF THE
INTERIOR MOUNTAIN WEST AND INTO THE GREAT PLAINS. THIS IS SUPPORTED BY THE
EVOLUTION OF THE WIND PETS FROM THE GEFS AND ECENS. THE ECENS PET INDICATES
INCREASED CHANCES OF WINDS EXCEEDING THE 85TH PERCENTILE ACROSS THE WEST INTO
GREAT PLAINS FROM THE ONSET OF THE WEEK-2 PERIOD. BY THE MIDDLE OF THE PERIOD,
THERE ARE INCREASED SIGNALS IN BOTH THE ECENS AND GEFS PETSR ACROSS MUCH OF THE
WEST AND GREAT PLAINS. THEREFORE, A BROAD SLIGHT RISK OF HIGH WINDS FORECAST
FOR MUCH OF THE INTERIOR WEST AND INTO THE HIGH PLAINS FOR THE ENTIRE WEEK-2
PERIOD.
AHEAD OF THE DEVELOPING TROUGH ACROSS THE WEST THERE A SURFACE LOW PRESSURE IS
FORECAST TO DEVELOP IN THE LEE OF THE ROCKIES. THIS SYSTEM WOULD BRING ELEVATED
CHANCES OF HEAVY RAIN AND SNOW, AND HIGH WINDS TO PARTS OF THE CENTRAL CONUS.
IN THE LOWER MISSISSIPPI VALLEY AND SURROUNDING AREAS THE PRECIPITATION HAZARD
WOULD LIKELY COME IN THE FORM OF HEAVY RAIN. THIS IS CONSISTENT WITH THE GEFS
AND ECENS PETS SHOWING INCREASED CHANCES FOR 3 DAY PRECIPITATION AMOUNTS
EXCEEDING THE 85TH PERCENTILE AND 1 INCH. FURTHER NORTH, FROM THE CENTRAL
ROCKIES STRETCHING THROUGH THE PLAINS AND MISSISSIPPI VALLEY INTO THE GREAT
LAKES, THERE IS ARE INCREASED CHANCES FOR HEAVY SNOW IN THESE AREAS. THIS IS
CONSISTENT WITH THE GEFS SNOW WATER EQUIVALENT (SWE) PET AND RAW GUIDANCE FROM
THE ECENS SHOWING THE POTENTIAL FOR A SWATH OF SNOW IN THIS REGION. FINALLY,
COLD AIR ADVECTION FOLLOWING THE FRONTAL PASSAGE AND STRONG PRESSURE GRADIENT
NEAR THE SURFACE LOW PRESSURE INCREASES THE RISK FOR HIGH WINDS ACROSS PARTS OF
THE CENTRAL AND SOUTHERN PLAINS, MIDDLE AND UPPER MISSISSIPPI VALLEY AND
WESTERN GREAT LAKES. THEREFORE, SLIGHT RISKS OF HEAVY RAIN, HEAVY SNOW, AND
HIGH WINDS ARE POSTED FOR THE PREVIOUSLY DESCRIBED REGIONS FOR JAN 18-20.
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 GREATEST CHANCES FOR HAZARDOUS HEAVY PRECIPITATION
AND HIGH WINDS TO BE REDUCED BY WEEK-2. AS SUCH, NO ASSOCIATED 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 15-16 FOR THIS REGION.
FINALLY, BY THE MIDDLE THROUGH THE END OF THE WEEK-2 PERIOD, THERE ARE
INCREASED SIGNALS FOR GAP WINDS TO DEVELOP IN SOUTHERN MAINLAND ALASKA WITH
STRONG SURFACE HIGH PRESSURE DEVELOPING IN THE MAINLAND OR OVER THE YUKON.
THEREFORE, A SLIGHT RISK OF HIGH WINDS IS POSTED FOR THE SOUTHERN MAINLAND
COAST FROM JAN 17-20.
FORECASTER: RYAN BOLT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page