871
FXUS21 KWNC 211917
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 21 2025
SYNOPSIS: A MAJOR TEMPERATURE CHANGE IS FORECAST BY THE END OF JANUARY WITH
NEAR TO ABOVE-NORMAL TEMPERATURES FAVORED FOR A MAJORITY OF THE LOWER 48 STATES
WHILE ANOMALOUSLY COLD TEMPERATURES PREVAIL ACROSS ALASKA. A TRANSITION TO A
MORE ZONAL FLOW PATTERN IS ANTICIPATED WHICH LOWERS THE RISK OF ANY WIDESPREAD,
HIGH IMPACT WINTER STORMS. BEGINNING ON JANUARY 30, ENHANCED ONSHORE FLOW IS
FORECAST TO RESULT IN PERIODS OF SNOW, POTENTIALLY HEAVY, TO THE CASCADES AND
NORTHERN ROCKIES.
HAZARDS
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR INTERIOR CENTRAL TO
SOUTHWESTERN ALASKA, WED-FRI, JAN 29-31.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF CENTRAL TO SOUTHERN
ALASKA, WED-TUE, JAN 29-FEB 4.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR NEW ENGLAND AND PARTS OF NEW
YORK, WED-FRI, JAN 29-31.
SLIGHT RISK OF HEAVY SNOW FOR THE NORTHERN CASCADES AND NORTHERN ROCKIES,
THU-TUE, JAN 30-FEB 4.
DETAILED SUMMARY
FOR FRIDAY JANUARY 24 - TUESDAY JANUARY 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JANUARY 29 - TUESDAY FEBRUARY 04: FOLLOWING AN ARCTIC OUTBREAK
THIS WEEK ACROSS THE EASTERN TWO THIRDS OF THE CONTIGUOUS U.S. (CONUS),
TEMPERATURES ARE LIKELY TO MODERATE PRIOR TO WEEK-2. THE GEFS AND ECENS ARE IN
GOOD AGREEMENT AND REMAIN CONSISTENT THAT NEGATIVE (POSITIVE) 500-HPA HEIGHT
ANOMALIES BECOME ESTABLISHED OVER THE HIGH (MIDDLE) LATITUDES OF NORTH AMERICA.
THIS POSITIVE ARCTIC OSCILLATION IS FORECAST BY THE GEFS TO PERSIST INTO THE
BEGINNING OF FEBRUARY, BUT ENSEMBLE SPREAD INCREASES AT THE END OF WEEK-2. THE
MADDEN-JULIAN OSCILLATION (MJO) IS FORECAST TO PROPAGATE EASTWARD FROM THE
INDIAN OCEAN TO THE MARITIME CONTINENT DURING THE NEXT TWO WEEKS AND THIS MJO
EVOLUTION TYPICALLY CORRESPONDS TO BELOW-NORMAL TEMPERATURES ACROSS ALASKA WITH
ABOVE-NORMAL TEMPERATURES MORE PREVALENT THROUGHOUT MUCH OF THE CONUS. MODEL
GUIDANCE IS CONSISTENT WITH THIS TEMPERATURE PATTERN DURING WEEK-2. MULTI-MODEL
ENSEMBLE MEANS FEATURE A HIGHLY AMPLIFIED RIDGE (TROUGH) OVER THE WESTERN
BERING SEA (MAINLAND ALASKA). THIS LONGWAVE PATTERN IS LIKELY TO PROMOTE CROSS
POLAR FLOW INTO ALASKA WITH THE GEFS AND ECENS HAVING THE ANOMALOUS COLD
PEAKING EARLY IN WEEK-2 WHEN DAILY TEMPERATURES ARE FORECAST TO AVERAGE NEAR
-25 DEGREES F BELOW NORMAL ACROSS SOUTHWESTERN ALASKA. THE GEFS AND ECENS
PROBABILISTIC EXTREME TOOLS (PETS) DEPICT MINIMUM TEMPERATURES HAVING MORE THAN
A 40 PERCENT CHANCE OF MINIMUM TEMPERATURES FALLING BELOW THE 15TH PERCENTILE
AND BELOW -20 DEGREES F, WHICH SUPPORTS A MODERATE RISK OF MUCH BELOW-NORMAL
TEMPERATURES FOR INTERIOR CENTRAL TO SOUTHWESTERN ALASKA FROM JANUARY 29 TO 31.
A BROADER SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES, VALID FOR THE ENTIRETY
OF WEEK-2, EXTENDS AS FAR SOUTH AS ANCHORAGE AND THE ALASKA PENINSULA. A STRONG
SURFACE HIGH CENTERED OVER NORTHEASTERN SIBERIA COUPLED WITH A SURFACE LOW
ACROSS THE GULF OF ALASKA IS EXPECTED TO RESULT IN ENHANCED NORTHERLY WINDS
ESPECIALLY EARLY IN WEEK-2. THESE ENHANCED WINDS MAY CAUSE WIND CHILL VALUES TO
EXCEED THE COLD ADVISORY CRITERIA OF -40F AND -55F ACROSS SOUTHERN AND CENTRAL
ALASKA, RESPECTIVELY.
BY THE START OF WEEK-2, THE ENSEMBLE MEANS DEPICT A 500-HPA TROUGH AMPLIFYING
OVER SOUTHEASTERN CANADA AND THE NORTHEASTERN CONUS WHICH IS LIKELY TO PROMOTE
ANOTHER SURGE OF ARCTIC AIR. A SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES,
VALID JANUARY 29-31, IS POSTED FOR PARTS OF NEW YORK AND NEW ENGLAND WHERE THE
GEFS AND ECENS DEPICT MINIMUM TEMPERATURES HAVING A 20 PERCENT CHANCE OF
FALLING BELOW THE 15TH PERCENTILE AND BELOW -10 DEGREES F. GUSTY NORTHWEST
WINDS COULD LEAD TO WIND CHILL VALUES BELOW -20 DEGREES F IN THE DESIGNATED
TEMPERATURE HAZARD. BY THE BEGINNING OF FEBRUARY, TEMPERATURES ARE FORECAST TO
RAPIDLY MODERATE AS THE ANOMALOUS 500-HPA TROUGH SHIFTS EASTWARD.
BEGINNING ON JANUARY 30 AND THROUGH THE END OF WEEK-2, THE GEFS AND ECENS FAVOR
ENHANCED ONSHORE FLOW INTO WASHINGTON, IDAHO, AND MONTANA WHICH MAY RESULT IN
PERIODS OF HEAVY SNOW FOR THE NORTHERN CASCADES AND NORTHERN ROCKIES. THE
SLIGHT RISK OF HEAVY SNOW IS CONSISTENT WITH WHERE THE GEFS PET HAS A 20
PERCENT CHANCE THAT 3-DAY SWE TOTALS EXCEED THE 85TH PERCENTILE AND 1 INCH,
LIQUID EQUIVALENT.
THE SLIGHT RISK OF HIGH WINDS FOR SOUTHERN CALIFORNIA WAS DISCONTINUED SINCE
THE ELEVATED RISK OF SANTA ANA WINDS IS EXPECTED TO TIME OFF BY THE BEGINNING
OF WEEK-2, JANUARY 29. AN AMPLIFIED TROUGH, EXTENDING FROM ALASKA SOUTHWARD TO
NEAR THE PACIFIC NORTHWEST, WOULD PROMOTE MORE ONSHORE FLOW ACROSS CALIFORNIA
DURING WEEK-2.
FORECASTER: BRAD PUGH
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