200
FXUS21 KWNC 241925
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 24 2025
SYNOPSIS: ARCTIC HIGH PRESSURE IS FORECAST TO SHIFT SOUTHWARD FROM ALASKA TO
THE NORTHERN GREAT PLAINS DURING EARLY FEBRUARY. MID-LEVEL LOW PRESSURE IS
LIKELY TO BRING PERIODS OF SNOW TO MUCH OF THE HIGHER ELEVATIONS OF THE WEST,
WHILE THE PATTERN BECOMES MORE FAVORABLE FOR A WINTER STORM TO AFFECT THE GREAT
PLAINS AND UPPER MIDWEST. FOLLOWING ANOMALOUSLY COLD TEMPERATURES ACROSS THE
SOUTHEAST THROUGH MUCH OF JANUARY, ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR
THIS REGION DURING THE FIRST WEEK OF FEBRUARY.
HAZARDS
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF CENTRAL TO SOUTHERN
ALASKA, SAT-MON, FEB 1-3.
SLIGHT RISK OF HIGH GAP WINDS FOR SOUTHEASTERN ALASKA, SUN-WED, FEB 2-5.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE NORTHERN GREAT PLAINS,
MON-FRI, FEB 3-7.
MODERATE RISK OF HEAVY SNOW FOR THE CASCADES, SAT-FRI, FEB 1-7.
SLIGHT RISK OF HEAVY SNOW FOR THE CASCADES AND NORTHERN SIERRA NEVADA
MOUNTAINS, SAT-FRI, FEB 1-7.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE WEST, SAT-FRI, FEB 1-7.
SLIGHT RISK OF HEAVY SNOW FOR THE GREAT BASIN, NORTHERN AND CENTRAL ROCKIES,
CENTRAL GREAT PLAINS, AND UPPER MIDWEST, SAT-FRI, FEB 1-7.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE LOWER MISSISSIPPI VALLEY,
TENNESSEE VALLEY, AND SOUTHERN APPALACHIANS, SAT-MON, FEB 1-3.
DETAILED SUMMARY
FOR MONDAY JANUARY 27 - FRIDAY JANUARY 31:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY FEBRUARY 01 - FRIDAY FEBRUARY 07: PRIOR TO THE START OF WEEK-2
(FEBRUARY 1), A HIGH AMPLITUDE 500-HPA RIDGE IS LIKELY TO PROMOTE ARCTIC HIGH
PRESSURE WITH AN INCREASED CHANCE OF MUCH BELOW-NORMAL TEMPERATURES FOR
PORTIONS OF CENTRAL TO SOUTHERN ALASKA. BASED ON THE GEFS AND ECENS
PROBABILISTIC EXTREME TOOLS (PETS) ALONG WITH PREDICTED DAILY TEMPERATURE
ANOMALIES, THE MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES IS DISCONTINUED
BUT THE SLIGHT RISK IS MAINTAINED THROUGH FEBRUARY 3. ANOMALOUS SURFACE HIGH
PRESSURE, CENTRED OVER THE YUKON OF WESTERN CANADA, SUPPORTS A SLIGHT RISK OF
HIGH GAP WINDS FOR SOUTHEASTERN ALASKA FROM FEBRUARY 2-5.
THE GEFS AND ECENS ARE IN GOOD AGREEMENT AND REMAIN CONSISTENT THAT ARCTIC HIGH
PRESSURE SHIFTS SOUTHWARD TO THE PACIFIC NORTHWEST, NORTHERN ROCKIES, AND
NORTHERN TO CENTRAL GREAT PLAINS AT THE BEGINNING OF FEBRUARY. A SLIGHT RISK OF
MUCH BELOW-NORMAL TEMPERATURES IS POSTED FOR THE NORTHERN TO CENTRAL GREAT
PLAINS WHERE THE GEFS AND ECENS PETS DEPICT MINIMUM TEMPERATURES HAVING A 20 TO
40 PERCENT CHANCE OF FALLING BELOW THE 15TH PERCENTILE AND -10 DEGREES F. A
MODERATE RISK IS NOT INCLUDED AT THIS TIME DUE TO THE LACK OF A FULL-LATITUDE
RIDGE UPSTREAM WHICH IS TYPICALLY ASSOCIATED WITH SUBSTANTIAL ARCTIC OUTBREAKS
AND THERE ARE MODEL DIFFERENCES ON THE PLACEMENT OF THE 500-HPA TROUGH AXIS
OVER WESTERN NORTH AMERICA.
THE BROAD TROUGH OVER WESTERN NORTH AMERICA AND THE GEFS SNOW WATER EQUIVALENT
(SWE) PET SUPPORT A SLIGHT RISK OF HEAVY SNOW FOR MANY OF THE HIGHER ELEVATIONS
OF THE WEST. COMPARED TO PREVIOUS DAYS, THE LATEST MODEL GUIDANCE PROMPTED A
SOUTHWARD EXPANSION OF THE SNOW HAZARD TO INCLUDE MORE OF COLORADO, UTAH, AND
THE NORTHERN SIERRA NEVADA MOUNTAINS. A MODERATE RISK OF HEAVY SNOW WAS ADDED
TO THE CASCADES WHERE THE GEFS AND ECENS HAVE THE HEAVIEST SNOWFALL AMOUNTS
FROM FEBRUARY 1-7 AND ONSHORE FLOW IS PREDICTED TO BE STRONGEST AT TIMES. BOTH
THE SLIGHT AND MODERATE RISKS OF HEAVY SNOWFALL OVER THE WEST ARE VALID THROUGH
THE ENTIRETY OF WEEK-2 DUE TO A PERSISTENT 500-HPA TROUGH. ALTHOUGH NO SNOW
HAZARD WAS POSTED FOR THE LOWER ELEVATIONS OF THE PACIFIC NORTHWEST, THE
500-HPA HEIGHT PATTERN FROM THE GEFS WOULD FAVOR AN INCREASED CHANCE OF
ACCUMULATING SNOW FOR THOSE AREAS ESPECIALLY IN WESTERN OREGON. THIS WILL BE
CLOSELY MONITORED IN SUBSEQUENT WEEK-2 HAZARDS OUTLOOKS. IN ADDITION TO THE
INCREASED CHANCE OF HEAVY SNOW, THE AMPLIFIED 500-HPA TROUGH WOULD LEAD TO
PERIODS OF ENHANCED WINDS, AND A SLIGHT RISK OF HIGH WINDS IS POSTED FROM THE
WEST COAST TO THE CONTINENTAL DIVIDE THROUGH THE END OF WEEK-2.
AS THE 500-HPA TROUGH AMPLIFIES OVER WESTERN NORTH AMERICA, THERE IS AN
INCREASING CHANCE OF SURFACE LOW DEVELOPMENT ACROSS THE CENTRAL GREAT PLAINS
WITH A LIKELY NORTHEASTWARD TRACK TO THE UPPER MIDWEST. THE GEFS PET DEPICTS
3-DAY SWE TOTALS HAVING MORE THAN A 20 PERCENT CHANCE OF EXCEEDING THE 85TH
PERCENTILE FOR THESE AREAS FOR MUCH OF WEEK-2. ALSO, A MAJORITY OF ECMWF
ENSEMBLE MEMBERS FEATURE A SWATH OF SNOWFALL FROM COLORADO NORTHEASTWARD
THROUGH THE CENTRAL GREAT PLAINS AND UPPER MIDWEST. BASED ON LONGWAVE PATTERN
RECOGNITION AND MODEL SNOWFALL TOOLS, A SLIGHT RISK OF HEAVY SNOW WAS
DESIGNATED FOR THE CENTRAL GREAT PLAINS AND UPPER MIDWEST THROUGH THE END OF
WEEK-2. UNCERTAINTY ON EXACT TIMING PRECLUDES THE DESIGNATION OF A MODERATE
RISK AT THIS TIME.
THE AMPLIFIED 500-HPA TROUGH UPSTREAM IS EXPECTED TO RESULT IN A SERIES OF LOW
PRESSURE SYSTEMS AND TRAILING FRONTS CROSSING THE CENTRAL AND EASTERN U.S.
DURING EARLY FEBRUARY. THE BEST MODEL AGREEMENT BETWEEN THE GEFS PET (3-DAY
AMOUNTS EXCEEDING THE 85TH PERCENTILE) AND ECENS (MORE THAN A 20 PERCENT CHANCE
OF 3-DAY AMOUNTS OF MORE THAN 1 INCH) OCCUR ACROSS THE LOWER MISSISSIPPI
VALLEY, TENNESSEE VALLEY, AND SOUTHERN APPALACHIANS FROM FEBRUARY 1-3. IN
ADDITION, ANTECEDENT WETNESS INCLUDING HIGH 28-DAY AVERAGE STREAMFLOWS ARE
PRESENT FOR PARTS OF ARKANSAS AND LOUISIANA. THE WETTER-THAN-NORMAL PATTERN FOR
THESE AREAS IS FAVORED TO CONTINUE THROUGH EARLY FEBRUARY.
FORECASTER: BRAD PUGH
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