288
FXUS21 KWNC 101905
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 10 2024
SYNOPSIS: A MAJOR ARCTIC AIR OUTBREAK IS FORECAST TO BE ONGOING ACROSS MUCH OF
THE EASTERN HALF OF THE CONTIGUOUS U.S. (CONUS) EARLY IN WEEK-2, BEFORE
MODERATING TOWARD THE END OF THE PERIOD. WHILE THE COLDEST TEMPERATURES ARE
FORECAST ACROSS THE NORTHERN TIER OF THE CONUS WITH LOW WIND CHILL VALUES
LIKELY RESULTING IN HAZARDOUS CONDITIONS, LARGE NEGATIVE TEMPERATURE ANOMALIES
AND SUBFREEZING TEMPERATURES ARE FORECAST TO EXTEND INTO PARTS OF THE DEEP
SOUTH. UPSTREAM, MID-LEVEL HIGH PRESSURE FORECAST ACROSS THE WEST COAST FAVORS
A RELATIVELY DRIER PATTERN, ALTHOUGH SHORTWAVE ENERGY MAY UNDERCUT THE
MID-LEVEL HIGH, POSSIBLY BRINGING UNSETTLED WEATHER TO CALIFORNIA AROUND THE
MIDDLE OF THE PERIOD.
HAZARDS
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE MIDWEST,
GREAT LAKES, TENNESSEE AND OHIO VALLEYS, APPALACHIANS, MID-ATLANTIC, AND
NORTHEAST, THU-SAT, JAN 18-20.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF THE CENTRAL AND
EASTERN CONUS EXCLUDING THE NORTHERN PLAINS AND SOUTHERN FLORIDA PENINSULA,
THU-MON, JAN 18-22
SLIGHT RISK OF HIGH WINDS OVER PORTIONS OF THE GREAT LAKES, OHIO VALLEY,
NORTHEAST, AND NORTHERN MID-ATLANTIC, THU-MON, JAN 18-22.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS MUCH OF CALIFORNIA, FRI-MON, JAN
19-22.
SLIGHT RISK OF HEAVY LAKE EFFECT SNOW DOWNWIND OF THE GREAT LAKES, THU-SAT, JAN
18-20.
DETAILED SUMMARY
FOR SATURDAY JANUARY 13 - WEDNESDAY JANUARY 17:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JANUARY 18 - WEDNESDAY JANUARY 24: FOLLOWING AN ACTIVE STORM TRACK
PATTERN IN THE EAST DURING WEEK-1, THE WEEK-2 PATTERN IS FORECAST TO BE
RELATIVELY DRIER WITH ARCTIC COLD ENTRENCHED ACROSS MUCH OF THE EASTERN CONUS
AS SURFACE HIGH PRESSURE SHIFTS TOWARD THE REGION. THE ECMWF AND GEFS
PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT PROBABILITIES GREATER THAN 40
PERCENT FOR MINIMUM TEMPERATURES FALLING BELOW THE 15TH CLIMATOLOGICAL
PERCENTILE ACROSS PARTS OF THE EAST ON 1/18. WHILE THE GEFS PET SLOWLY DECAYS
THESE HIGHER PROBABILITIES AS WEEK-2 PROGRESSES, THE ECMWF PET DEPICTS A
RENEWED SHOT OF COLD AIR BEGINNING AROUND 1/19 WITH PROBABILITIES FOR MINIMUM
TEMPERATURES FALLING BELOW THE 15TH PERCENTILE INCREASING ABOVE 60 PERCENT
ACROSS PARTS OF THE MIDWEST AND SOUTHEASTERN CONUS BY THE MIDDLE OF THE PERIOD.
THE ECMWF SOLUTION WOULD FAVOR INCREASED CHANCES FOR SUBFREEZING TEMPERATURES
ALONG THE GULF OF MEXICO COAST AND OVER NORTHERN FLORIDA DURING THIS TIMEFRAME.
THE GEFS, HOWEVER, IS MORE TONED DOWN, RESULTING IN DECREASED CONFIDENCE
REGARDING THE EXTENT OF THE COLD. FARTHER TO THE NORTH, PROBABILITIES FOR
MINIMUM TEMPERATURES REACHING HAZARDOUS THRESHOLDS IN PERCENTILE SPACE
DECREASE. HOWEVER, INCREASED WIND SPEEDS COMBINED WITH RELATIVELY COLDER
TEMPERATURES ARE LIKELY TO LEAD TO HAZARDOUS WIND CHILLS WARRANTING A MORE
NORTHWARD EXPANSION OF THE TEMPERATURE HAZARDS THAN WHAT THE PETS WOULD
SUPPORT. THIS INCLUDES ACROSS PARTS OF THE OHIO VALLEY, MID-ATLANTIC, AND
NORTHEAST WHERE SUBZERO WIND CHILLS ARE POSSIBLE (BELOW -20 DEG F ACROSS PARTS
OF INTERIOR NEW ENGLAND, THE GREAT LAKES, AND UPPER MISSISSIPPI VALLEY).
GIVEN THE DECREASED PROBABILITIES IN THE PETS EARLY IN THE PERIOD COMPARED TO
YESTERDAY, THE HIGH RISK FOR MUCH BELOW NORMAL TEMPERATURES IS DISCONTINUED.
THE MODERATE RISK CONTINUES ACROSS PORTIONS OF THE MIDWEST, GREAT LAKES,
TENNESSEE AND OHIO VALLEYS, APPALACHIANS, MID-ATLANTIC, AND NORTHEAST
1/18-1/20. IF AGREEMENT BETWEEN THE GEFS AND ECMWF IMPROVES REGARDING AN
ADDITIONAL BURST OF COLD AIR TOWARD THE MIDDLE OF WEEK-2, THE MODERATE RISK MAY
NEED TO BE FURTHER EXPANDED INTO PARTS OF THE DEEP SOUTH AND SOUTHEAST, BUT
HOLDING OFF AT THIS TIME GIVEN THE RELATIVELY WARMER TEMPERATURES FORECAST IN
THESE AREAS EARLY IN WEEK-2 COMPARED TO LATE WEEK-1. THE SLIGHT RISK INCLUDES
MUCH OF THE EASTERN CONUS (EXCLUDING PARTS OF THE NORTHERN PLAINS AND SOUTH
FLORIDA) AND IS DISCONTINUED AFTER 1/22 AS SIGNALS FOR HAZARDOUS COLD DECREASE
WITH HINTS OF MORE RIDGING AND A POSSIBLY WARMER PATTERN BUILDING INTO THE EAST
TOWARD THE END OF JANUARY TIED TO THE MJO PROGRESSION INTO THE MARITIME
CONTINENT AND WESTERN PACIFIC. THE POSSIBLE FLOODING HAZARD IS DISCONTINUED
ACROSS THE EAST DUE TO A DRIER PATTERN BEGINNING LATE IN WEEK-1, ALONG WITH
MANY AREAS HAVING TEMPERATURES BELOW FREEZING WHICH FAVORS REDUCED SNOW MELT.
STRONG WINDS ARE LIKELY TO ACCOMPANY THE INCOMING COLD, PARTICULARLY ACROSS THE
NORTHERN TIER OF THE CONUS WHERE PRESSURE GRADIENTS ARE FORECAST TO BE HIGHER
DUE TO LOWER PRESSURE OVER SOUTHEASTERN CANADA AND HIGHER PRESSURE ACROSS THE
SOUTHEAST. THESE WINDS MAY APPROACH HAZARDOUS THRESHOLDS (GREATER THAN A 20
PERCENT CHANCE OF EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 20-MPH BASED
ON THE ECMWF PET OVER SOME AREAS), WHICH WOULD ALSO CONTRIBUTE TO THE
AFOREMENTIONED VERY LOW WIND CHILL VALUES. THE SLIGHT RISK OF HIGH WINDS IS
POSTED ACROSS PORTIONS OF THE GREAT LAKES, OHIO VALLEY, NORTHEAST, AND
NORTHERN MID-ATLANTIC FOR JAN 18-22. THE ELEVATED WIND SPEEDS MAY ALSO TRIGGER
EPISODES OF HEAVY LAKE EFFECT SNOW DOWNWIND OF THE GREAT LAKES GIVEN LITTLE ICE
COVER, NEAR-RECORD WARM LAKE SURFACE TEMPERATURES, AND THE COLD AIR MASS MOVING
OVERHEAD. THEREFORE, A SLIGHT RISK OF HEAVY SNOW IS HIGHLIGHTED OVER AREAS TO
THE SOUTHEAST OF THE GREAT LAKES FOR JAN 18-20.
UPSTREAM, RIDGING IS FORECAST TO BUILD ACROSS THE WESTERN CONUS EARLY IN
WEEK-2, WHICH FAVORS DECREASING CHANCES FOR HEAVY PRECIPITATION. THIS IS
REFLECTED IN THE GEFS AND ECMWF PETS WHICH DEPICT REDUCED PROBABILITIES (LESS
THAN 20 PERCENT) FOR PRECIPITATION TOTALS REACHING THE 85TH CLIMATOLOGICAL
PERCENTILE ACROSS THE PACIFIC NORTHWEST. FURTHER SOUTH, THE SIGNAL IS MORE
ENHANCED, DUE IN PART TO THE DECREASED PRECIPITATION CLIMATOLOGY. HOWEVER,
SHORTWAVE TROUGHING UNDERCUTTING THE RIDGE MAY LEAD TO PERIODS OF HEAVIER
PRECIPITATION ACROSS CALIFORNIA AROUND THE MIDDLE OF THE PERIOD, WITH BOTH THE
GEFS AND ECMWF PETS INDICATING PROBABILITIES GREATER THAN 20 PERCENT FOR 3-DAY
PRECIPITATION TOTALS EXCEEDING ONE INCH OVER SOME AREAS. GIVEN THE MARGINAL
NATURE OF THE THREAT AND LIMITED SUPPORT FROM THE VARIOUS FORECAST TOOLS, NO
ADDITIONAL RELATED WIND OR SNOW HAZARDS ARE POSTED ACROSS THE WEST IN TODAY’S
OUTLOOK, ALTHOUGH COASTAL HIGH WINDS AND HIGH ELEVATION SNOW CANNOT BE RULED
OUT IF AN ENHANCED MOISTURE FEED REACHES CALIFORNIA.
A MORE TRANQUIL PATTERN IS PREDICTED ACROSS ALASKA COMPARED TO THE CONUS, WITH
AMPLIFIED MID-LEVEL RIDGING FORECAST OVER THE BERING SEA. THIS FAVORS INCREASED
CHANCES FOR BELOW-NORMAL PRECIPITATION ACROSS WESTERN ALASKA. WHILE
PRECIPITATION CHANCES ARE INCREASED ACROSS THE SOUTHEASTERN PART OF THE STATE
RELATED TO ENHANCED ONSHORE FLOW, PRECIPITATION TOTALS ARE UNLIKELY TO REACH
HAZARDOUS THRESHOLDS.
FORECASTER: THOMAS COLLOW
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