985
FXUS21 KWNC 041957
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 04 2024
SYNOPSIS: A HIGHLY AMPLIFIED MEAN MID-LEVEL PATTERN OVER NORTH AMERICA IS
EXPECTED TO INCREASE THE RISK FOR MANY WEATHER-RELATED HAZARDS THROUGHOUT THE
CONTIGUOUS U.S. (CONUS). ANOTHER LOW PRESSURE SYSTEM FAVORED MAY LEAD TO HEAVY
PRECIPITATION AND EPISODES OF HIGH WINDS ACROSS THE EASTERN U.S. WITH THE
POTENTIAL FOR HEAVY ACCUMULATING SNOW OVER THE GREAT LAKES AND MIDWEST EARLY IN
THE PERIOD. SURFACE HIGH PRESSURE FORECAST TO DESCEND FROM SOUTHERN CANADA
SIGNALS THE POTENTIAL FOR AN ARCTIC AIR OUTBREAK OVER MUCH OF THE WESTERN AND
CENTRAL CONUS. ENHANCED ATMOSPHERIC MOISTURE OVER THE WEST IS EXPECTED TO
PROMOTE HIGH ELEVATION SNOWFALL, AND THE POSSIBLE RETURN OF HEAVY PRECIPITATION
ACROSS THE WEST COAST.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR THE SOUTHEAST AND MUCH OF THE EASTERN
SEABOARD, FRI-SAT, JAN 12-13.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE SOUTHEAST, AND THE EASTERN SEABOARD,
FRI-SUN, JAN 12-14.
SLIGHT RISK OF HEAVY SNOW OVER PARTS OF THE GREAT PLAINS, MIDDLE AND UPPER
MISSISISSIPPI AND OHIO VALLEYS, GREAT LAKES, AND NORTHEAST, FRI-MON, JAN 12-15.
SLIGHT RISK OF HIGH WINDS FOR MANY PARTS OF THE NORTHEASTERN CONUS, FRI-MON,
JAN 12-15.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MANY PARTS OF THE ROCKIES,
GREAT PLAINS, AND MISSISSIPPI VALLEY, FRI-SUN, JAN 12-14.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF THE WESTERN AND
CENTRAL CONUS, FRI-THU, JAN 12-18.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE WESTERN AND CENTRAL CONUS, FRI-TUE,
JAN 12-16.
MODERATE RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF THE FOUR CORNERS,
FRI-SAT, JAN 12-13.
SLIGHT RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF THE FOUR CORNERS,
FRI-SUN, JAN 12-14.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA, SUN-THU, JAN 14-18.
SLIGHT RISK OF HEAVY SNOW FOR THE CASCADES, KLAMATH/SISKIYOU AND SIERRA
MOUNTAINS, SUN-THU, JAN 14-18.
SLIGHT RISK OF HEAVY SNOW FOR MANY PARTS OF NORTHERN GREAT BASIN, NORTHERN
INTERMOUNTAIN, CENTRAL AND NORTHERN ROCKIES, FRI-THU, JAN 12-18.
SLIGHT RISK OF HIGH WINDS FOR THE ALEUTIANS, ALASKA PENINSULA, SOUTHCENTRAL AND
SOUTHWESTERN MAINLAND COAST FROM FRI-SUN, JAN 12-14.
FLOODING POSSIBLE FOR MOST OF THE ATLANTIC COAST STATES FROM NORTHERN FLORIDA
TO CENTRAL NEW ENGLAND.
DETAILED SUMMARY
FOR SUNDAY JANUARY 07 - THURSDAY JANUARY 11:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JANUARY 12 - THURSDAY JANUARY 18: THE WEEK-2 HAZARDS PERSPECTIVE
MOSTLY REMAINS ON TRACK SINCE YESTERDAY, AS THERE ARE MULTIPLE WEATHER RELATED
HAZARD RISKS ASSOCIATED WITH DEEPLY AMPLIFIED MEAN 500-HPA TROUGHING FEATURED
IN THE DYNAMICAL MODELS OVER MUCH OF THE CONUS. FOLLOWING THE EXIT OF A MAJOR
STORM SYSTEM OVER THE NORTHEASTERN CONUS LATE IN WEEK-1, BOTH THE GEFS AND
ECMWF ENSEMBLES CONTINUE TO FAVOR THE REDEVELOPMENT OF SURFACE LOW PRESSURE
OVER THE MIDWEST BY LATE NEXT WEEK. WITH FAIRLY STRONG SURFACE RETURN FLOW
ESTABLISHED OVER THE SOUTHEAST, A MODERATE RISK OF HEAVY PRECIPITATION REMAINS
POSTED (JAN 12-13) AND IS EXPANDED NORTHWARD INTO PARTS OF THE NORTHEAST WHERE
PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT ELEVATED CHANCES (30-50%) FOR 3-DAY
PRECIPITATION AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 1 INCH. WITHIN THE
HIGHLIGHTED MODERATE RISK AREA ACROSS THE SOUTH, DETERMINISTIC SOLUTIONS
CONTINUE TO SUGGEST THE POTENTIAL FOR THUNDERSTORM ACTIVITY ALONG THE PREDICTED
FRONTAL BOUNDARY. COMPARED TO YESTERDAY, ENSEMBLES GENERALLY FAVOR A MORE
NORTHERLY MEAN SOLUTION OF THE SURFACE LOW TRACK, WHICH IS LIKELY TIED TO
HIGHER MID-LEVEL HEIGHTS FAVORED IN THE MODELS OVER THE WESTERN ATLANTIC. THIS
IS EXPECTED TO LEAVE MUCH OF THE EASTERN SEABOARD IN THE WARM SECTOR AND SHIFT
THE HEAVY SNOW POTENTIAL INTO PORTIONS OF THE GREAT LAKES AND THE MIDWEST EARLY
IN THE PERIOD. AS A RESULT, A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS POSTED
OVER THE EASTERN SEABOARD (JAN 12-14) AND IS EXPANDED WESTWARD INTO THE OHIO
VALLEY AND EASTERN GREAT LAKES. SIMILARLY, A SLIGHT RISK OF HEAVY SNOW REMAINS
ISSUED (JAN 12-15) WITH MOST OF ITS COVERAGE NOW FOCUSED OVER THE MIDWEST AND
GREAT LAKES CONSISTENT WITH THE LATEST UNCALIBRATED SNOW GUIDANCE AND THE GEFS
SNOW WATER EQUIVALENT (SWE) PET. IT IS WORTH NOTING THAT MIXED PRECIPITATION
TYPES ARE POSSIBLE ALONG THE SOUTHERN PERIPHERY OF THE HIGHLIGHTED AREA.
ADDITIONALLY, A SLIGHT RISK OF HIGH WINDS REMAINS ISSUED COVERING MUCH OF THE
NORTHEASTERN CONUS GIVEN THE POTENTIAL FOR STRENGTHENING PRESSURE GRADIENTS AND
SUPPORT FROM GEFS AND ECMWF PETS.
DUE TO THE SHORT RETURN INTERVAL OF STORM SYSTEMS FORECAST TO BRING
ABOVE-NORMAL PRECIPITATION OVER THE EAST COAST DURING THE NEXT TWO WEEKS,
SUBSTANTIAL PRECIPITATION SURPLUSES IN EXCESS OF 5 INCHES REGISTERED DURING THE
PAST 30-DAYS, AND WELL AS THE POTENTIAL FOR RAIN ON ANTECEDENT SNOW PACK, A
FLOODING POSSIBLE HAZARD REMAINS ISSUED FOR MOST OF THE ATLANTIC COAST STATES
FROM NORTHERN FLORIDA TO CENTRAL NEW ENGLAND.
AIDED BY STRONGER MID-LEVEL RIDGING NOW FAVORED OVER THE BERING STRAIT
UPSTREAM, A CONSEQUENCE OF THE AFOREMENTIONED TRENDS FEATURED IN TODAY'S
GUIDANCE IS THE INCREASED POTENTIAL FOR THE ADVECTION OF ARCTIC AIR INTO MUCH
OF THE WESTERN AND CENTRAL CONUS. THERE ARE BETTER INDICATIONS IN THE ENSEMBLES
FOR STRONG SURFACE HIGH PRESSURE DESCENDING FROM THE CANADIAN PRAIRIES, WITH A
WIDESPREAD STRENGTHENING OF NEGATIVE TEMPERATURE DEPARTURES OVER THE INTERIOR
WEST, GREAT PLAINS AND MISSISSIPPI VALLEY EARLY IN THE PERIOD. THIS TREND IS
ALSO REFLECTED IN BOTH THE GEFS AND ECMWF PETS INDICATING AT LEAST A 40% (20%)
CHANCE FOR MINIMUM TEMPERATURES FALLING BELOW THE 15TH (5TH) PERCENTILE. BASED
ON THESE COLD SIGNALS, THE ADDITION OF A HIGH RISK FOR MUCH BELOW NORMAL
TEMPERATURES WAS CONSIDERED, BUT GIVEN THEIR NOVELTY, AND DIFFERENCES BETWEEN
THE GEFS AND ECMWF SOLUTIONS LATER IN THE PERIOD, A MODERATE RISK DESIGNATION
WAS DEEMED APPROPRIATE FOR MANY PORTIONS OF ROCKIES, GREAT PLAINS AND
MISSISSIPPI VALLEY IN THE OUTLOOK FOR JAN 12-14. THIS RISK POTENTIAL WILL BE
EVALUATED IN SUBSEQUENT HAZARD OUTLOOKS. BEYOND DAYS 10 AND 11 (JAN 14-15),
INCREASED CHANCES FOR HAZARDOUS COLD PERSIST IN THE PETS THROUGH THE END OF
THE PERIOD, BUT THE GEFS AND ECMWF DIVERGE IN REGARDS TO THE EVOLUTION AND
STRENGTH OF THE COLD SIGNALS AS THE TROUGHING ALOFT DEAMPLIFIES AND FLATTENS.
TO ADDRESS THE UNCERTAINTY AT THIS LEAD, A BROAD SLIGHT RISK AREA OF MUCH BELOW
NORMAL TEMPERATURES REMAINS ISSUED FOR MUCH OF THE WESTERN AND CENTRAL CONUS
FOR THE ENTIRETY OF WEEK-2. THE PREVAILING MID-LEVEL PATTERN ALSO SUPPORTS THE
CONTINUATION OF A BROAD SLIGHT RISK AREA OF HIGH WINDS FOR MUCH OF THE WESTERN
AND CENTRAL CONUS FOR JAN 12-16. THE COMBINATION OF ANOMALOUS COLD AND ELEVATED
WIND SPEEDS ARE LIKELY TO BRING VERY LOW WIND CHILLS WITHIN THE HIGHLIGHTED
MODERATE RISK REGION. BIAS CORRECTED TOOLS SHOW THE INCREASED CHANCES FOR WIND
CHILL VALUES BELOW -20 AND -40 DEGREES F OVER PARTS OF THE CENTRAL AND NORTHERN
HIGH PLAINS.
WITH ENHANCED TROPOSPHERIC MOISTURE LINGERING FROM WEEK-1 INTO WEEK-2, THE
DEEPLY AMPLIFIED TROUGHING ALOFT FAVORED OVER THE INTERIOR WEST LATE NEXT WEEK
SUPPORTS THE CONTINUATION OF A MODERATE RISK AREA OF HIGH ELEVATION SNOW OVER
THE FOUR CORNERS REGION FOR JAN 12-13. AS THE PATTERN BECOMES MORE ZONAL,
CONDITIONS ARE EXPECTED TO BE RELATIVELY DRIER OVER THE SOUTHWESTERN CONUS FOR
THE REMAINDER OF THE PERIOD, PROMPTING THE DISCONTINUATION OF THE ENVELOPING
SLIGHT RISK AREA FOR HEAVY SNOW OVER THIS PART OF THE COUNTRY AFTER DAY 10.
HOWEVER, THERE ARE GROWING INDICATIONS IN THE ENSEMBLES FOR ANOMALOUS TROUGHING
UNDERCUTTING A AMPLIFIED RIDGE FAVORED UPSTREAM OVER NORTHERN PACIFIC, RENEWING
THE POTENTIAL FOR ENHANCED ONSHORE FLOW AND POSSIBLE ATMOSPHERIC RIVER ACTIVITY
OVER THE WEST COAST BY NEXT WEEKEND. BASED ON INCREASING SIGNALS AND INTEGRATED
VAPOR TRANSPORT TOOLS (IVTS) AND PETS, A SLIGHT RISK OF HEAVY PRECIPITATION
REMAINS ISSUED OVER THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA, ALONG WITH A
SLIGHT RISK OF HEAVY SNOW OVER THE HIGHER ELEVATIONS OF THE SIERRA NEVADAS AND
CASCADES OF THE WEST COAST, BOTH VALID FOR JAN 14-18. WITH AN ELEVATED RISK OF
HIGH WINDS ALSO IN PLACE, THIS MAY LEAD TO COASTAL EROSION AND HIGH SURF OVER
PARTS OF THE WEST COAST. GUIDANCE GENERALLY SHOWS A REINFORCEMENT OF ENHANCED
TROPOSPHERIC MOISTURE OVER NORTHERN HALF OF THE INTERIOR WEST THROUGH THE END
OF WEEK-2, AND A SLIGHT RISK OF HIGH ELEVATION SNOW IS ISSUED OVER PARTS OF THE
GREAT BASIN, NORTHERN INTERMOUNTAIN, AND ROCKIES FOR JAN 12-18, WHICH IS ALSO
SUPPORTED BY THE GEFS SWE.
IN ALASKA, PERSISTENT MID-LEVEL AND SURFACE LOW PRESSURE OVER THE BERING SEA
FAVORS A SLIGHT RISK OF HIGH WINDS FOR THE ALEUTIANS, ALASKA PENINSULA,
SOUTHWESTERN MAINLAND, AND SOUTH-CENTRAL COAST FOR JAN 12-14. WHAT BEARS
WATCHING IS THE DEVELOPMENT OF STRONG SURFACE HIGH PRESSURE OVER THE YUKON OF
NORTHWESTERN CANADA, WHICH MAY INDUCE GAP WINDS OVER THE SOUTHEAST LATER IN THE
PERIOD. OVER HAWAII, GUIDANCE CONTINUES TO FAVOR KONA LOW FORMATION DURING
WEEK-1, THOUGH MUCH OF THE HEAVIEST PRECIPITATION THREAT LOOKS TO TIME OFF BY
LATE NEXT WEEK, AND NO CORRESPONDING HAZARDS ARE ISSUED.
FORECASTER: NICK NOVELLA
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