898
FXUS21 KWNC 031929
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 03 2024
SYNOPSIS: A VERY ACTIVE WEATHER PATTERN IS IN STORE ACROSS THE UNITED STATES
DURING THE WEEK-2 OUTLOOK PERIOD. AT THE START OF WEEK-2, A MAJOR WINTER STORM
IS PREDICTED TO EXIT THE EASTERN SEABOARD, ACCOMPANIED BY A WIDE VARIETY OF
WEATHER-RELATED HAZARDS. A NEW AREA OF PRECIPITATION IS THEN EXPECTED TO
DEVELOP OVER THE SOUTHEAST AND TRACK NORTHEASTWARD. STORMINESS IS FORECAST TO
CONTINUE OVER THE WEST, WITH RAIN AT LOWER ELEVATIONS AND MOUNTAIN SNOWS.
SURFACE LOW PRESSURE OVER THE BERING SEA IS EXPECTED TO BRING HIGH WINDS TO THE
ALEUTIANS, THE ALASKA PENINSULA AND THE SOUTH-CENTRAL COAST, WHILE A
SIGNIFICANT RAIN-PRODUCER IS FORECAST TO INFLUENCE THE HAWAIIAN ISLANDS DURING
THE FIRST FEW DAYS OF THE PERIOD, WITH HEAVY RAINFALL AND POTENTIAL FLOODING.
HAZARDS
SLIGHT RISK OF HEAVY SNOW OVER PARTS OF THE GREAT LAKES, MID-ATLANTIC, AND THE
NORTHEAST, THU, SAT-MON, JAN 11, 13-15.
SLIGHT RISK OF HEAVY SNOW OVER PARTS OF THE MIDDLE MISSISSIPPI AND OHIO
VALLEYS, GREAT LAKES, APPALACHIANS, AND MID-ATLANTIC, SAT-SUN, JAN 13-14.
MODERATE RISK OF HIGH WINDS OVER THE NORTHEAST, THU, JAN 11.
SLIGHT RISK OF HIGH WINDS FOR MANY PARTS OF THE NORTHEASTERN CONUS, THU-FRI,
SUN-MON, JAN 11-12, JAN 14-15.
MODERATE RISK OF HEAVY PRECIPITATION FOR THE SOUTHEAST AND THE LOWER 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 MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF THE WESTERN AND
CENTRAL CONUS, THU-WED, JAN 11-17.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE WESTERN AND CENTRAL CONUS, THU-WED,
JAN 11-17.
SLIGHT RISK OF HEAVY SNOW FOR THE CASCADES, KLAMATH/SISKIYOU AND SIERRA
MOUNTAINS, THU-WED, JAN 11-17.
MODERATE RISK OF HEAVY SNOW FOR THE HIGHER ELEVATIONS OF THE LOWER FOUR
CORNERS, THU-SAT, JAN 11-13.
SLIGHT RISK OF HEAVY SNOW FOR MANY HIGHER ELEVATIONS OF THE WESTERN CONUS,
THU-WED, JAN 11-17.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA, SAT-WED, JAN 13-17.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE HAWAIIAN ISLANDS, THU-FRI, JAN 11-12.
SLIGHT RISK OF HIGH WINDS FOR THE ALEUTIANS, ALASKA PENINSULA, SOUTHCENTRAL AND
SOUTHWESTERN MAINLAND COAST FROM THU-MON, JAN 11-15.
FLOODING POSSIBLE FOR MOST OF THE ATLANTIC COAST STATES FROM NORTHERN FLORIDA
TO CENTRAL NEW ENGLAND.
DETAILED SUMMARY
FOR SATURDAY JANUARY 06 - WEDNESDAY JANUARY 10:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JANUARY 11 - WEDNESDAY JANUARY 17: LATE IN WEEK-1, THERE IS GOOD
CONTINUITY IN THE DYNAMICAL MODELS FAVORING A POTENT LOW PRESSURE SYSTEM
EXITING THE NORTHEASTERN CONUS. WHILE THE HEAVIEST PRECIPITATION AMOUNTS ARE
EXPECTED TO TIME OFF BY THE START OF THE PERIOD, THERE REMAINS A LINGERING
THREAT OF HEAVY SNOW ON THE BACKSIDE OF THE DEPARTING LOW GIVEN CONTINUED
SUPPORT IN THE RAW GUIDANCE. THUS, A SLIGHT RISK OF HEAVY SNOW REMAINS ISSUED
FOR DAY 8 (JAN 11) OVER PARTS OF NEW ENGLAND WITH COVERAGE EXTENDING INTO THE
GREAT LAKES DUE TO LAKE EFFECT SNOW POTENTIAL (JAN 11). STRENGTHENING SURFACE
PRESSURE GRADIENTS ARE LIKELY IN THE WAKE OF THE SYSTEM AND BASED ON PRESSURE
TRENDS IN BOTH THE GEFS AND ECMWF ENSEMBLES, A MODERATE RISK OF WINDS ALSO
REMAINS POSTED FOR JAN 11 FOCUSED OVER NEW ENGLAND, WITH A BROAD SLIGHT RISK
AREA OF HIGH WINDS COVERING MUCH OF THE NORTHEASTERN CONUS, VALID FOR JAN
11-12.
WITH DEEPLY AMPLIFIED 500-HPA TROUGHING FAVORED TO BE ESTABLISHED THROUGHOUT
MUCH OF NORTH AMERICA, CONTINUED SHORTWAVE ACTIVITY ALONG THE MEAN TROUGH AXIS
SUPPORTS ADDITIONAL SURFACE LOW DEVELOPMENT OVER THE CENTRAL AND EASTERN CONUS
NOT LONG AFTER THE LATE WEEK-1 SYSTEM LIFTS OUT. THERE IS GOOD CONTINUITY IN
THE ENSEMBLES DEPICTING MOIST, RETURN FLOW FROM THE GULF OF MEXICO TAKING SHAPE
ON DAYS 8 AND 9, WITH ENHANCED PRECIPITATION AMOUNTS ALONG ANOTHER FRONTAL
BOUNDARY OVER THE LOWER EASTERN SEABOARD. THE HEAVY PRECIPITATION POTENTIAL IS
WELL REFLECTED IN THE PROBABILISTIC EXTREMES TOOLS (PETS) WHERE BOTH THE GEFS
AND ECMWF SHOW AT LEAST 20 TO 30% CHANCES FOR 3-DAY PRECIPITATION AMOUNTS
EXCEEDING THE 85TH PERCENTILE AND 1 INCH. HIGHER CHANCES (>40%) ARE INDICATED
IN THE ECMWF BASED PET, AND GIVEN THE PREVAILING MID-LEVEL HEIGHT PATTERN, A
MODERATE RISK FOR HEAVY PRECIPITATION REMAINS ISSUED (JAN 12-13) FROM THE
MID-ATLANTIC TO THE SOUTHEAST WITH A BROAD SLIGHT RISK AREA OF HEAVY
PRECIPITATION ENVELOPING THE ENTIRE EASTERN SEABOARD THROUGH DAY 11 (JAN 14).
BASED ON THE LATEST GUIDANCE, THUNDERSTORM ACTIVITY WITHIN THE MODERATE RISK
AREA CANNOT BE RULED OUT.
AS THE ASSOCIATED SURFACE LOW IS FAVORED TO TAKE A SIMILAR TRACK OVER THE
GREAT LAKES AND NORTHEAST AND DEEPEN TOWARDS THE MIDDLE OF WEEK-2, THE RETURN
OF STRENGTHENING PRESSURE GRADIENTS SUPPORT EPISODES OF HIGH WINDS. THUS, THE
BROAD SLIGHT RISK AREA PREVIOUSLY HIGHLIGHTED OVER THE NORTHEASTERN CONUS IS
AGAIN VALID FOR DAYS 11 AND 12 (JAN 14-15) TIED TO THIS ADDITIONAL SYSTEM. WITH
RESIDUAL MOISTURE AND COLD AIR ADVECTION FAVORED, ACCUMULATING SNOWFALL IS
AGAIN POSSIBLE ON THE BACKSIDE OF THE DEPARTING LOW. A SECONDARY AREA OF HEAVY
SNOW IS POSTED (JAN 13-14) WHERE THE GEFS SNOW WATER EQUIVALENT PET SHOWS
INCREASED CHANCES FOR VALUES EXCEEDING THE 85TH PERCENTILE OVER PARTS OF THE
MIDWEST EAST TO THE MID-ATLANTIC, WITH THE RISK OF HEAVY SNOW SHIFTING
NORTHWARD OVER THE NORTHEASTERN CONUS, VALID FOR JAN 13-15.
PRIOR TO THE WEEK-2 PERIOD, HEAVY SNOWFALL IS EXPECTED FOR AT LEAST INTERIOR
SECTIONS OF THE NORTHEAST AND MID-ATLANTIC REGION, IN ADDITION TO HEAVY RAIN.
AS MUCH OF THE EAST COAST HAS EXPERIENCED PRECIPITATION SURPLUSES OF 5-10
INCHES (OR GREATER) DURING THE PAST 30-DAYS, THE EXPECTED RAIN ON TOP OF SNOW
PREDICTED TO BE ALREADY DEPOSITED, IN ADDITION TO WARMER TEMPERATURES
ANTICIPATED WITHIN THE STORM'S WARM SECTOR, WARRANT A POTENTIAL FLOOD RISK FOR
MOST OF THE ATLANTIC COAST STATES FROM NORTHERN FLORIDA TO CENTRAL NEW ENGLAND.
UPSTREAM IN THE WAKE OF STORM SYSTEMS IN THE EAST, BOTH THE GEFS AND ECMWF
ENSEMBLES SHOW THE POTENTIAL FOR STRONG SURFACE HIGH PRESSURE SPILLING DOWN
FROM THE CANADIAN PRAIRIES INTO THE HIGHER ELEVATIONS OF THE WEST AND GREAT
PLAINS. THE ADVECTION OF ANOMALOUSLY COLD WINTER AIR IS SUPPORTED IN THE RAW
TEMPERATURE GUIDANCE, AS WELL AS THE GEFS AND ECWMF PETS, BUT THESE TOOLS
DIFFER ON THE MAGNITUDE AND SPATIAL EXTENT OF THE HAZARDOUS COLD POTENTIAL (THE
ECMWF FAVORS A STRONGER AND MORE SOUTHEASTERLY REACH OF THE COLD SIGNAL). TO
RECONCILE THESE DIFFERENCES, A BROAD SLIGHT RISK OF MUCH BELOW NORMAL
TEMPERATURES IS POSTED OVER MUCH OF THE WESTERN AND CENTRAL CONUS FOR THE
ENTIRETY OF WEEK-2 WHERE BOTH TOOLS SHOW AT LEAST A 20% CHANCE OF MINIMUM
TEMPERATURES FALLING BELOW THE 15TH PERCENTILE. THESE TOOLS ALSO SHOW AN
INCREASED POTENTIAL FOR NIGHTTIME LOWS FALLING BELOW FREEZING IN THE SOUTHERN
PLAINS, AND BELOW ZERO OVER THE NORTHERN HIGH PLAINS. GIVEN THE AMPLIFYING
TROUGHING ALOFT AND SUPPORT FROM THE WIND BASED PETS, A BROAD SLIGHT RISK AREA
OF HIGH WINDS IS ALSO POSTED FOR MUCH OF THE WESTERN AND CENTRAL CONUS. THE
COMBINATION OF ANOMALOUS COLD AND ELEVATED WIND SPEEDS ARE LIKELY TO BRING VERY
LOW WIND CHILLS FOR AREAS WEST OF THE MISSISSIPPI. BIAS CORRECTED TOOLS SHOW
THE INCREASED CHANCES FOR WIND CHILL VALUES DIPPING WELL BELOW THEIR
CLIMATOLOGICAL NORMAL VALUES OVER THE FOUR CORNERS AND BELOW -20 DEGREES F OVER
THE NORTHERN HIGH PLAINS.
OVER THE EASTERN PACIFIC, ANOMALOUS RIDGING FAVORED UPSTREAM FAVORS ENHANCED
ONSHORE FLOW TO PROMOTE ANOMALOUS MOISTURE OVERSPREADING MUCH OF THE WESTERN
CONUS. BASED ON CONTINUED SUPPORT FROM THE SWE GEFS PET, A PAIR OF SLIGHT
RISKS FOR HIGH ELEVATION HEAVY SNOW REMAIN ISSUED FOR PARTS OF THE WEST COAST
AND OVER MUCH OF THE ROCKIES OF THE INTERIOR WEST FOR THE ENTIRETY OF WEEK-2.
COMPARED TO YESTERDAY, THERE ARE INCREASED WET SIGNALS IN THE PETS WITH 40%
CHANCES FOR 3-DAY PRECIPITATION AMOUNTS EXCEEDING THE 85TH PERCENTILE FOCUSED
OVER THE LOWER FOUR CORNERS EARLY IN THE PERIOD. THEREFORE, A MODERATE RISK OF
HIGH ELEVATION HEAVY SNOW IS POSTED MAINLY OVER THE MOGOLLON RIM AND EXTENDING
INTO NEW MEXICO FOR JAN 11-13. ACROSS THE WEST COAST, THERE ARE DIFFERENCES
BETWEEN THE GEFS AND ECWMF PETS IN REGARDS TO HEAVY PRECIPITATION POTENTIAL
WITH THE LATTER FAVORING A DRIER SOLUTION OVER THE CALIFORNIA AND THE PACIFIC
NORTHWEST. HOWEVER, BASED ON INCREASED SIGNALS IN THE INTEGRATED VAPOR
TRANSPORT (IVT) TOOLS, THERE IS A MODEST POTENTIAL FOR THE ONSET OF ATMOSPHERIC
RIVER ACTIVITY DURING THE MIDDLE OF THE PERIOD, AND A SLIGHT RISK OF HEAVY
PRECIPITATION REMAINS POSTED FOR JAN 13-17. 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 DURING THE PERIOD.
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, AND
SOUTH-CENTRAL COAST FOR JAN 11-15. IN HAWAII, MODELS CONTINUE TO SHOW
INDICATIONS OF A KONA LOW FORMING WHICH MAY RESULT IN HEAVY PRECIPITATION AND
POTENTIAL FLOODING FOR THE HAWAIIAN ISLANDS FOR JAN 11-12. SOME MODEL GUIDANCE
SUGGESTS THE BULK OF THE RAINFALL MAY REMAIN JUST TO THE NORTH OF THE
ARCHIPELAGO.
FORECASTER: NICK NOVELLA
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