405
FXUS21 KWNC 112029
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 11 2024
SYNOPSIS: A MAJOR ARCTIC AIR OUTBREAK IS FORECAST TO BE ONGOING ACROSS MUCH OF
THE EASTERN HALF OF THE CONTIGUOUS U.S. (CONUS) AT THE OUTSET OF 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. A COASTAL STORM MAY IMPACT PARTS OF THE NORTHEAST EARLY IN THE PERIOD.
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 EARLY IN WEEK-2.
HAZARDS
HIGH RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE MIDDLE
MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, APPALACHIANS, AND THE SOUTHEAST,
FRI-SAT, JAN 19-20.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE
MISSISSIPPI, TENNESSEE AND OHIO VALLEYS, APPALACHIANS, SOUTHEAST, AND
MID-ATLANTIC, FRI-SUN, JAN 19-21.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF THE CENTRAL AND
EASTERN CONUS EXCLUDING THE NORTHERN PLAINS AND SOUTHERN FLORIDA PENINSULA,
FRI-MON, JAN 19-22.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS MUCH OF CALIFORNIA, FRI-SUN, JAN
19-21.
SLIGHT RISK FOR HEAVY PRECIPITATION ACROSS PORTIONS OF THE SOUTHERN PLAINS,
TENNESSEE AND LOWER MISSISSIPPI VALLEYS, AND SOUTHEAST, MON-WED, JAN 22-24.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE NORTHEAST, FRI-SAT, JAN 19-20.
SLIGHT RISK OF HEAVY LAKE EFFECT SNOW DOWNWIND OF THE GREAT LAKES, FRI-SAT, JAN
19-20.
SLIGHT RISK OF HEAVY SNOW ACROSS THE SIERRA NEVADA MOUNTAINS, FRI-SUN, JAN
19-21.
SLIGHT RISK OF HIGH WINDS ALONG THE WEST COAST, FRI-SUN, JAN 19-21.
MODERATE RISK OF HIGH WINDS OVER PORTIONS OF THE NORTHEAST, FRI-SUN, JAN 19-21.
SLIGHT RISK OF HIGH WINDS OVER PORTIONS OF THE GREAT LAKES, OHIO VALLEY,
NORTHEAST, AND NORTHERN MID-ATLANTIC, FRI-MON, JAN 19-22.
DETAILED SUMMARY
FOR SUNDAY JANUARY 14 - THURSDAY JANUARY 18:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JANUARY 19 - THURSDAY JANUARY 25: ARCTIC COLD IS FORECAST TO BE
ENTRENCHED ACROSS MUCH OF THE EASTERN CONUS AT THE OUTSET OF WEEK-2. THERE IS
IMPROVING AGREEMENT AMONG THE MODELS REGARDING A RENEWED BURST OF COLD AIR
EARLY IN WEEK-2, WITH THE ECMWF PROBABILISTIC EXTREMES TOOL (PET) DEPICTING AT
LEAST A 60 PERCENT CHANCE MINIMUM TEMPERATURES FALL BELOW THE 15TH
CLIMATOLOGICAL PERCENTILE EXTENDING ACROSS THE MIDWEST AND INTO THE SOUTHEAST.
WHILE PROBABILITIES IN THE GEFS PET ARE RELATIVELY LOWER (UPWARDS OF 40
PERCENT), THIS IS AN INCREASE COMPARED TO YESTERDAY. SUBZERO TEMPERATURES ARE
POSSIBLE ACROSS THE MIDWEST AND CORNBELT STARTING ON 1/19, WITH THE ANOMALOUS
COLD THEN FORECAST TO EXPAND SOUTHEASTWARD, WITH PARTS OF THE DEEP SOUTH
POTENTIALLY HAVING MINIMUM TEMPERATURES LESS THAN 20 DEG F STARTING ON 1/20,
AND SUBFREEZING TEMPERATURES POSSIBLY EXTENDING TO THE GULF COAST AND NORTHERN
FLORIDA. DUE TO THESE INCREASING SIGNALS, A HIGH RISK FOR MUCH BELOW NORMAL
TEMPERATURES IS POSTED ACROSS PARTS OF THE MIDDLE MISSISSIPPI, OHIO AND
TENNESSEE VALLEYS, APPALACHIANS, AND SOUTHEAST 1/19-1/20. THE MODERATE RISK
CONTINUES ACROSS PORTIONS OF THE MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS,
APPALACHIANS, SOUTHEAST, AND MID-ATLANTIC 1/19-1/21, AND IS EXTENDED THROUGH
THE GULF OF MEXICO COAST. THE SLIGHT RISK INCLUDES MUCH OF THE CENTRAL AND
EASTERN CONUS, WITH LOW WIND CHILLS BEING THE MAJOR CONCERN ACROSS THE NORTHERN
TIER DESPITE PROBABILITIES FOR REACHING HAZARDOUS TEMPERATURES IN THE PETS
BEING LOWER COMPARED TO FURTHER SOUTH. 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). THE SLIGHT RISK IS DISCONTINUED AFTER 1/22 AS
SIGNALS FOR HAZARDOUS COLD DECREASE DUE TO MORE RIDGING AND A POSSIBLY WARMER
PATTERN BUILDING INTO THE EAST DURING LATE-JANUARY ASSOCIATED WITH THE MJO
PROGRESSION INTO THE MARITIME CONTINENT AND WESTERN PACIFIC.
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 19-22, WITH A MODERATE RISK FOR HIGH WINDS POSTED ACROSS
THE NORTHEAST JAN 19-21 CORRESPONDING WITH WHERE THE STRONGEST PRESSURE
GRADIENT IS FORECAST. 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 19-20. THE 0Z ECMWF ENSEMBLE ALSO
INDICATES INCREASED POTENTIAL FOR A COASTAL LOW PRESSURE SYSTEM TO DEVELOP
ACROSS THE NORTHEAST, WITH SOME AREAS HAVING AT LEAST A 20 PERCENT CHANCE OF
SNOWFALL GREATER THAN 4 INCHES, ALTHOUGH THE 12Z ECMWF ENSEMBLE HAS BACKED OFF
SOMEWHAT. A SLIGHT RISK OF HEAVY SNOW HAS BEEN ADDED ACROSS PARTS OF THE
NORTHEAST FOR JAN 19-20, ALTHOUGH UNCERTAINTY REMAINS HIGH GIVEN LIMITED
SUPPORT FROM THE GEFS AND CANADIAN.
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 AND SOUTHWESTERN OREGON EARLY IN 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,
SUPPORTING THE SLIGHT RISK OF HEAVY PRECIPITATION ACROSS MOST OF THE STATE JAN
19-21. A CORRESPONDING SLIGHT RISK OF HEAVY SNOW IS ALSO POSTED ACROSS THE
SIERRA NEVADA FOR THE SAME TIME PERIOD. THE GEFS SNOW WATER EQUIVALENT (SWE)
PET INDICATES SOME ELEVATED POTENTIAL FOR SWE GREATER THAN THE 85TH
CLIMATOLOGICAL PERCENTILE ACROSS THE FOUR CORNERS DURING THE MIDDLE OF THE
PERIOD AS THE UPSTREAM ENERGY MOVES INLAND. HOWEVER, ACTUAL SNOWFALL AMOUNTS
ARE FAVORED TO BE ON THE LOWER SIDE, AND NO RELATED SNOW HAZARD IS POSTED AT
THIS TIME. A SLIGHT RISK FOR HIGH WINDS IS ALSO HIGHLIGHTED ALONG THE WEST
COAST JAN 19-21, WITH THE ECMWF PET DEPICTING AT LEAST A 20 PERCENT CHANCE WIND
SPEEDS EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 25-MPH.
AS THE AFOREMENTIONED MID-LEVEL DISTURBANCE CONTINUES TO MOVE EASTWARD, ALONG
WITH RETURN SOUTHERLY FLOW FAVORED ACROSS THE SOUTH-CENTRAL AND SOUTHEASTERN
CONUS AS THE COLD AIR MASS DECAYS, THERE ARE INCREASING SIGNALS FOR HEAVY
PRECIPITATION. BOTH THE GEFS AND ECMWF PET DEPICT A BROAD REGION OF THE
SOUTHERN PLAINS, LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND SOUTHEAST HAVING
AT LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION EXCEEDS THE 85TH
CLIMATOLOGICAL PERCENTILE AND 1-INCH TOWARD THE SECOND HALF OF WEEK-2.
THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED ACROSS THESE AREAS
JAN 22-24, CONSISTENT WITH THE STRONGEST SIGNALS IN THE UNCALIBRATED 0Z ECMWF,
GEFS, AND CANADIAN ENSEMBLES. WHILE ENOUGH WARM AIR SHOULD MOVE IN BY THIS TIME
TO FAVOR RAIN, IT IS NOT OUT OF THE QUESTION THAT ENOUGH COLD COULD REMAIN IN
PLACE TO SUPPORT SNOW ALONG THE NORTHERN AREAS OF THIS SHAPE.
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 SOUTHERN AND EASTERN PARTS OF
THE STATE RELATED TO ENHANCED ONSHORE FLOW, PRECIPITATION TOTALS ARE UNLIKELY
TO REACH HAZARDOUS THRESHOLDS.
FORECASTER: THOMAS COLLOW
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