463
FXUS21 KWNC 241909
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 24 2024
SYNOPSIS: AN AREA OF SURFACE LOW PRESSURE AND ASSOCIATED COLD FRONT IS FORECAST
TO RING IN THE NEW YEAR ACROSS THE EAST COAST WITH SLIGHT CHANCES OF HEAVY
PRECIPITATION ALONG COASTAL NEW ENGLAND, WITH HEAVY SNOW POSSIBLE FOR THE
INTERIOR NORTHEAST, AND POTENTIAL HIGH WINDS FOR MUCH OF THE EAST COAST. IN THE
PACIFIC NORTHWEST, THERE MAY BE ANOTHER STORM THAT WILL MOVE INTO THE AREA
BRINGING RAIN, HIGH ELEVATION SNOW, AND A PERIOD OF HIGH WINDS. ONE OR MORE
STORM SYSTEMS COULD INCREASE SNOW CHANCES FOR MUCH OF THE ROCKIES WESTERN GREAT
PLAINS.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF COASTAL NORTHEAST AND
MID-ATLANTIC, WED-THU, JAN 1-2.
SLIGHT RISK OF HEAVY HEAVY SNOW FOR THE INTERIOR NORTHEAST AND DOWNWIND OF
LAKES ERIE AND ONTARIO, WED-THU, JAN 1-2.
SLIGHT RISK OF HIGH WINDS FOR THE NORTHEAST, MID-ATLANTIC, AND PARTS OF THE
SOUTHEAST WED-THU, JAN 1-2.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE PACIFIC NORTHWEST,
WED-FRI, JAN 1-3.
SLIGHT RISK OF HEAVY SNOW FOR HIGH ELEVATIONS OF THE CASCADES, WED-FRI, JAN 1-3.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE NORTHWEST, WED-FRI, JAN 1-3.
SLIGHT RISK OF HEAVY SNOW FOR MUCH OF THE ROCKIES AND WESTERN GREAT PLAINS,
WED-SUN, JAN 1-5.
DETAILED SUMMARY
FOR FRIDAY DECEMBER 27 - TUESDAY DECEMBER 31:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JANUARY 01 - TUESDAY JANUARY 07: THE FORECAST MID-LEVEL HEIGHT
PATTERN OVER THE CONTIGUOUS U.S. IS RATHER UNCERTAIN TODAY. THE MAIN DRIVER OF
THE UNCERTAINTY IS THE EVOLUTION OF A WEAK MID-LEVEL TROUGH NEAR THE WEST COAST
PRIOR TO THE WEEK-2 PERIOD. THE ECENS IS MORE PROGRESSIVE, BRINGING THIS TROUGH
TO THE EASTERN CONUS BY THE ONSET OF WEEK-2, WHILE THE GEFS IS SLOWER,
MAINTAINING THE NEGATIVE 500-HPA HEIGHT ANOMALIES ACROSS THE ROCKIES AND
WESTERN PLAINS. A MORE PROGRESSIVE PATTERN WOULD FAVOR INCREASED CHANCES FOR A
STRONGER SURFACE LOW PRESSURE ACROSS THE NORTHEASTERN CONUS AND STRONG
MID-LEVEL RIDGING ACROSS THE WEST. A SLOWER PATTERN WOULD INCREASE
PRECIPITATION CHANCES ACROSS THE ROCKIES AND PLAINS EARLY IN THE PERIOD.
THE MORE PROGRESSIVE ECENS TROUGH IS FORECAST TO UNDERCUT A MID-LEVEL RIDGE
OVER EASTERN CANADA AND PROMOTE A STRONG SURFACE LOW OVER THE EASTERN CONUS.
THIS STORM SYSTEM, EARLY IN WEEK-2, WOULD BRING CHANCES FOR HEAVY RAIN ALONG
PORTIONS OF COASTAL NEW ENGLAND. THEREFORE, A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED FOR PORTIONS OF COASTAL NEW ENGLAND FOR JAN 1 & 2. THE
ECENS AND GEFS PROBABILISTIC EXTREMES TOOLS (PETS) INDICATE A 20-40% CHANCE OF
3-DAY ACCUMULATED PRECIPITATION EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE
AND .75 INCHES IN THE HAZARD AREA. FURTHER INLAND, THE RAW ECENS FORECASTS
ELEVATED CHANCES FOR 3 DAY SNOW TOTALS TO EXCEED 6 INCHES. THEREFORE AN
ASSOCIATED RISK OF HEAVY SNOW IS POSTED FOR PORTIONS OF INTERIOR NEW ENGLAND
FOR THE SAME PERIOD. FINALLY, THIS AREA OF SURFACE LOW PRESSURE MAY INCREASE
WIND SPEEDS ACROSS MUCH OF THE NORTHEAST AND MID-ATLANTIC AS THE COLD FRONT
PUSHES THROUGH. THIS IS CONSISTENT WITH THE ECENS AND CANADIAN PETS WHICH BOTH
HAVE INCREASED CHANCES OF WIND SPEEDS EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE. THEREFORE, A SLIGHT RISK OF HIGH WINDS IS POSTED FOR JAN 1 & 2 FOR
MUCH OF THE NORTHEAST, MID-ATLANTIC, AND PARTS OF THE SOUTHEAST.
IN THE PACIFIC NORTHWEST, ONE OR MORE SHORTWAVES ARE FORECAST TO PROGRESS
THROUGH THE REGION ALONG THE PERIPHERY OF A MID-LEVEL RIDGE FORECAST ACROSS THE
WESTERN CONUS EARLY IN THE WEEK-2 PERIOD. THIS INCREASES CHANCES FOR HEAVY
PRECIPITATION, HIGH ELEVATION SNOW, AND EPISODIC HIGH WINDS. THERE IS A FAIR
AMOUNT OF UNCERTAINTY REGARDING THE STRENGTH OF THESE SHORTWAVES AND AVAILABLE
MOISTURE. THE GEFS AND ECENS PETS INDICATE CHANCES FOR PRECIPITATION TO EXCEED
THE 85TH CLIMATOLOGICAL PERCENTILE AND 2 INCHES ACROSS MUCH OF THE REGION ALONG
AND WEST OF THE CASCADES. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS
POSTED FOR AREAS WEST OF THE MOUNTAINS, WITH A SLIGHT RISK OF HEAVY SNOW FOR
THE HIGHER ELEVATIONS OF THE CASCADES FOR JAN 1-3. A CORRESPONDING SLIGHT RISK
OF HIGH WINDS IS POSTED FOR AREAS ALONG AND WEST OF THE CASCADES WITH THE ECENS
PET FORECASTING STRONG CHANCES OF WINDS EXCEEDING THE 85TH PERCENTILE, AGAIN
FOR JAN 1-3.
THE SLOWER PROGRESSION OF A MID-LEVEL TROUGH IN THE GEFS INCREASES CHANCES FOR
HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN ROCKIES EARLY IN THE
WEEK-2 PERIOD. THE GEFS PETS PRECIPITATION AND SNOW WATER EQUIVALENT (SWE) TOOL
HIGHLIGHT THIS RISK ALONG WITH THE POTENTIAL FOR A SURFACE LOW TO EJECT OUT OF
THE SOUTHERN ROCKIES. THE GEFS PET FORECAST INCREASED CHANCES FOR 3 DAY
PRECIPITATION AMOUNTS TO EXCEED THE 85TH PERCENTILE AND 1 INCH ACROSS PARTS OF
THE LOWER MISSISSIPPI VALLEY ASSOCIATED WITH THIS WAVE OF LOW PRESSURE BUT WITH
NO SUPPORT FROM THE ECENS THERE IS NO HAZARD POSTED AT THIS TIME. FURTHER
NORTH, THE SHORTWAVE TROUGHS WILL PROGRESS INLAND AND LIKEWISE INCREASES
CHANCES FOR HEAVY SNOW ACROSS THE NORTHERN ROCKIES. THEREFORE, A BROAD SLIGHT
RISK OF HEAVY SNOW IS POSTED FOR THE ROCKIES AND WESTERN GREAT PLAINS FOR JAN
1-5 DUE TO THE GENERAL UNCERTAINTY OF HOW THE PATTERN WILL EVOLVE BUT WITH THE
POTENTIAL FOR AN IMPACTFUL STORM TO DEVELOP.
ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY, THE GEFS PET SHOWS AT
LEAST A 20% CHANCE OF MINIMUM TEMPERATURES FALLING BELOW THE 15TH PERCENTILE
AND 0 DEGF. THE ECENS PET HAS INCREASED CHANCES OF TEMPERATURES FALLING BELOW
THE 15TH PERCENTILE TODAY RELATIVE TO YESTERDAY. HOWEVER, ADVISORY LEVEL COLD
HAZARDS REQUIRE APPARENT TEMPERATURES NEAR -30 DEGF IN THESE REGIONS AND
APPARENT TEMPERATURES SEEM UNLIKELY TO REACH THESE THRESHOLDS AT THIS TIME.
THEREFORE, NO CORRESPONDING HAZARD IS POSTED BUT THIS AREA WILL CONTINUE TO BE
MONITORED.
IN SOUTHERN CALIFORNIA, THERE IS SOME SUGGESTION OF AN INVERTED TROUGH NEAR THE
COAST IN SOME OF THE ENSEMBLE GUIDANCE. HOWEVER, MOST OF THE MODEL GUIDANCE
DOES NOT INDICATE STRONG HIGH PRESSURE FORMING OVER THE GREAT BASIN AT THIS
TIME WHICH WOULD LIMIT THE POTENTIAL OF ANY SANTA ANA WIND THREAT AT THIS TIME.
IN ALASKA, ABOVE-NORMAL PRECIPITATION IS FORECAST ACROSS THE SOUTHERN MAINLAND.
HOWEVER, PETS DO NOT INDICATE ELEVATED CHANCES FOR PRECIPITATION TO EXCEED 2
INCHES DURING ANY 3 DAY PERIOD DURING WEEK-2. THUS, NO CORRESPONDING HAZARD IS
FORECAST AT THIS TIME. SIMILARLY, THE ECENS PET SHOWS SIGNALS FOR WINDS TO
EXCEED THE 85TH PERCENTILE IN SOUTHERN MAINLAND ALASKA, BUT THE HIGHEST WIND
SPEEDS ARE LIKELY TO REMAIN OFFSHORE RESULTING IN NO ASSOCIATED HAZARD BEING
POSTED.
FORECASTER: RYAN BOLT
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