999
FXUS21 KWNC 091919
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 09 2024
SYNOPSIS: THERE IS INCREASING CONFIDENCE FOR A MAJOR ARCTIC AIR OUTBREAK ACROSS
MUCH OF THE CONTIGUOUS U.S. (CONUS) DURING WEEK-2. 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
SOUTHWARD THROUGH THE GULF COAST, WITH RECORD COLD TEMPERATURES POSSIBLE IN
SOME AREAS. EPISODES OF HEAVY PRECIPITATION REMAIN POSSIBLE ALONG THE WEST
COAST THROUGHOUT WEEK-2, PERHAPS SHIFTING SOUTHWARD TOWARD CALIFORNIA LATER IN
THE PERIOD, ALTHOUGH CONFIDENCE REMAINS LOW DUE TO CONTINUED DIFFERENCES IN THE
MODEL GUIDANCE.
HAZARDS
HIGH RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL AND
SOUTHERN PLAINS, MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, SOUTHEAST,
APPALACHIANS, AND INTERIOR NORTHEAST, WED, JAN 17.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF THE EASTERN HALF OF
THE CONUS, EXCLUDING PARTS OF THE NORTHERN PLAINS, UPPER MISSISSIPPI VALLEY,
AND THE CENTRAL AND SOUTHERN FLORIDA PENINSULA, WED-SAT, JAN 17-20.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR THE NORTHERN ROCKIES AND MUCH
OF THE CENTRAL AND EASTERN CONUS EXCLUDING THE SOUTHERN FLORIDA PENINSULA,
WED-MON, JAN 17-22
SLIGHT RISK OF HIGH WINDS OVER PORTIONS OF THE GREAT LAKES, OHIO VALLEY,
NORTHEAST, AND NORTHERN MID-ATLANTIC, WED-FRI, JAN 17-19.
SLIGHT RISK OF EPISODES OF HIGH WINDS ALONG THE WEST COAST, WED-TUE, JAN 17-23.
SLIGHT RISK OF HEAVY PRECIPITATION OVER NORTHERN CALIFORNIA AND THE PACIFIC
NORTHWEST, WED-SAT, JAN 17-20.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS MUCH OF CALIFORNIA, SAT-TUE, JAN
20-23.
SLIGHT RISK OF HIGH ELEVATION HEAVY SNOW OVER THE SIERRA NEVADAS, KLAMATH
MOUNTAINS, AND THE CASCADES OF THE WEST COAST, WED-SAT, JAN 17-20.
SLIGHT RISK OF HEAVY SNOW OVER THE HIGHER ELEVATIONS OF THE GREAT BASIN,
NORTHERN INTERMOUNTAIN, CENTRAL AND NORTHERN ROCKIES, WED-SAT, JAN 17-20.
SLIGHT RISK OF HEAVY LAKE EFFECT SNOW DOWNWIND OF THE GREAT LAKES, WED-FRI, JAN
17-19.
POSSIBLE FLOODING FOR MOST OF THE EAST COAST STATES FROM NORTHERN FLORIDA TO
CENTRAL NEW ENGLAND.
DETAILED SUMMARY
FOR FRIDAY JANUARY 12 - TUESDAY JANUARY 16:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JANUARY 17 - TUESDAY JANUARY 23: STRONG HIGH-LATITUDE BLOCKING
ASSOCIATED WITH POSITIVE 500-HPA HEIGHT ANOMALIES ACROSS NORTHERN CANADA AND
GREENLAND AND NEGATIVE HEIGHT ANOMALIES OVER THE CONUS IS FORECAST TO PERSIST
THROUGH MID-JANUARY. DURING WEEK-1, MULTIPLE AREAS OF SURFACE LOW PRESSURE ARE
FORECAST TO BRING ROUNDS OF HEAVY PRECIPITATION AND HIGH WINDS TO PARTS OF THE
EASTERN CONUS. HOWEVER, AS THE MEAN LONGWAVE TROUGHING SHIFTS MORE EASTWARD,
THIS ACTIVE STORM TRACK IS FAVORED TO SUBSIDE, WITH SOME INDICATION OF A FINAL
SYSTEM AROUND 1/16 BEFORE A DRIER, BUT COLDER PATTERN EMERGES. MODELS CONTINUE
TO DIFFER WITH THE EVOLUTION OF THIS SYSTEM, WITH THE 0Z ECMWF DEPICTING A
SIGNIFICANT EAST COAST SNOWSTORM LATE IN WEEK-1, AND THE 12Z GFS INDICATING A
MUCH MORE SUBDUED SYSTEM. GIVEN THAT THE ANY ELEVATED POTENTIAL FOR HEAVY
PRECIPITATION IS MORE FOCUSED PRIOR TO THE START OF WEEK-2, THE BROAD SLIGHT
RISK FOR HEAVY SNOW ACROSS THE EAST IS REMOVED IN TODAY’S OUTLOOK, ALTHOUGH A
MORE AMPLIFIED SYSTEM AS DEPICTED IN THE 0Z ECMWF COULD LEAD TO HEAVY SNOW
LINGERING ACROSS THE NORTHEAST INTO DAY-8 (1/17). GIVEN THE HIGH ANTECEDENT
PRECIPITATION TOTALS PREDICTED ACROSS THE EAST IN WEEK-1, THE FLOODING POSSIBLE
HAZARD REMAINS HIGHLIGHTED ACROSS THE EAST FOR WEEK-2, WITH RIVER LEVELS LIKELY
REMAINING ELEVATED INTO THE START OF THE PERIOD.
FOLLOWING THE DEPARTURE OF THE SYSTEM LATE IN WEEK-1, ARCTIC COLD IS FORECAST
TO SPREAD THROUGHOUT MUCH OF THE EASTERN CONUS AS SURFACE HIGH PRESSURE EXTENDS
TOWARD THE GULF OF MEXICO COAST. FOR MANY AREAS, THE COLDEST TEMPERATURES OF
THE SEASON THUS FAR ARE FORECAST TO OCCUR EARLY IN WEEK-2, COINCIDING WITH THE
CLIMATOLOGICAL COLDEST TIME OF THE YEAR. THE ECMWF PROBABILISTIC EXTREMES TOOL
(PET) DEPICTS PROBABILITIES GREATER THAN 60 PERCENT FOR MINIMUM TEMPERATURES
FALLING BELOW THE 15TH PERCENTILE ACROSS THE EAST-CENTRAL AND SOUTHEASTERN
PLAINS, OHIO AND TENNESSEE VALLEYS, THE DEEP SOUTH, AND INTO FLORIDA ON DAY-8
(1/17), WITH SOME AREAS POSSIBLY EXPERIENCING RECORD COLD. THIS ALSO COINCIDES
WITH ELEVATED PROBABILITIES OF SUBFREEZING TEMPERATURES REACHING THE GULF OF
MEXICO COAST, WITH 20 PERCENT OR GREATER PROBABILITIES OF TEMPERATURES FALLING
BELOW 40 DEG F EXTENDING THROUGH SOUTH-CENTRAL FLORIDA. THE GEFS PET IS NOT AS
ROBUST COMPARED TO THE ECMWF IN TERMS OF PROBABILITIES BUT DEPICTS THE SAME
GENERAL EVOLUTION AND PLACEMENT OF THE COLDEST TEMPERATURES. FARTHER TO THE
NORTH, PROBABILITIES FOR MINIMUM TEMPERATURES REACHING HAZARDOUS THRESHOLDS IN
PERCENTILE SPACE DECREASE COMPARED TO AREAS TO THE SOUTH. 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, UPPER
MISSISSIPPI VALLEY, AND NORTHERN PLAINS).
A HIGH RISK OF MUCH BELOW NORMAL TEMPERATURES IS POSTED ON DAY-8 (1/17) ACROSS
PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS, MISSISSIPPI, OHIO, AND TENNESSEE
VALLEYS, SOUTHEAST, APPALACHIANS, AND INTERIOR NORTHEAST COINCIDING WITH THE
HIGHEST PROBABILITIES IN THE PETS, ANTECEDENT SNOW COVER, AND INCREASED
POTENTIAL FOR LOW WIND CHILL VALUES FOR NORTHERN AREAS. THE MODERATE RISK AREA
IS MORE EXPANSIVE AND INCLUDES MUCH OF THE EASTERN HALF OF THE CONUS, AND
EXTENDS THROUGH DAY-11 (1/20). THE ECMWF ENSEMBLE REBUILDS THE ANOMALOUS COLD
ACROSS THE MIDWEST AROUND THE MIDDLE OF THE PERIOD, WHILE THE SIGNAL SLOWLY
MODERATES IN THE GEFS. THE SLIGHT RISK INCLUDES THE NORTHERN ROCKIES AND NEARLY
ALL OF THE CONUS EAST OF THE ROCKIES, AND IS VALID THROUGH DAY-13 (1/22), AFTER
WHICH 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.
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 PRESSURES OVER SOUTHEASTERN CANADA AND HIGHER PRESSURES ACROSS THE
SOUTHEAST. THESE WINDS MAY APPROACH HAZARDS THRESHOLDS (GREATER THAN A 20
PERCENT CHANCE FOR EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 20-MPH
BASED ON THE ECMWF PET OVER SOME AREAS), AND WILL 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 17-19. 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 17-19.
UPSTREAM, DESPITE THE MORE ANOMALOUS RIDGING GENERALLY FAVORED OVER THE WESTERN
CONUS COMPARED TO EARLIER ENSEMBLE MEAN GUIDANCE, BOTH THE GEFS AND ECMWF
FEATURE THE POTENTIAL FOR INTERMITTENT ROUNDS OF SHORTWAVE ENERGY ALLOWING FOR
PERIODS OF ENHANCED ONSHORE FLOW OVER PARTS OF THE WEST COAST. THE GEFS PET IS
MORE BULLISH ACROSS THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA EARLY IN THE
PERIOD, DEPICTING AT LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION TOTALS
EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-2 INCHES. THESE ELEVATED
PROBABILITIES SHIFT SOUTHWARD TOWARD CALIFORNIA LATER IN WEEK-2. THE ECMWF PET
DOES NOT DEPICT AS STRONG OF A PRECIPITATION SIGNAL AS THE GEFS PET ACROSS THE
PACIFIC NORTHWEST EARLY IN THE PERIOD, BUT DOES INDICATE INCREASING
PROBABILITIES ACROSS CALIFORNIA BY THE END OF THE PERIOD. GIVEN THESE TRENDS, A
SLIGHT RISK OF HEAVY PRECIPITATION IS HIGHLIGHTED ACROSS THE PACIFIC NORTHWEST
AND NORTHERN CALIFORNIA JAN 17-20, WITH A SECOND SLIGHT RISK POSTED ACROSS MUCH
OF CALIFORNIA JAN 20-23. A SLIGHT RISK OF HEAVY SNOW REMAINS POSTED OVER THE
SIERRA NEVADAS, KLAMATH MOUNTAINS, AND THE CASCADES OF THE WEST COAST FOR JAN
17-20 AND TRENDS WILL BE MONITORED FOR A POSSIBLE SOUTHWARD EXPANSION LATER IN
WEEK-2. MODEST SIGNALS FOR ATMOSPHERIC RIVER ACTIVITY ALSO SUPPORT A SLIGHT
RISK OF HIGH WINDS FOR THE WEST COAST DURING WEEK-2. GIVEN SUPPORT FOR ENHANCED
TROPOSPHERIC MOISTURE SPREADING EASTWARD INTO THE INTERIOR WEST, A SLIGHT RISK
OF HIGH ELEVATION HEAVY SNOW IS POSTED FOR PARTS OF THE GREAT BASIN, NORTHERN
INTERMOUNTAIN, AND THE ROCKIES FOR JAN 16-22.
A MUCH 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 MUCH OF WESTERN ALASKA,
ALONG WITH NEAR- TO SLIGHTLY ABOVE-NORMAL TEMPERATURES. NO HAZARDS ARE
INDICATED ACROSS THE STATE.
FORECASTER: THOMAS COLLOW
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