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FXUS21 KWNC 122003
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 12 2025
SYNOPSIS: STRONG SURFACE HIGH PRESSURE DESCENDING FROM CANADA IS EXPECTED TO
BRING A SHOT OF ARCTIC AIR, ELEVATING THE RISK OF HAZARDOUSLY COLD TEMPERATURES
ACROSS MANY PARTS OF THE CENTRAL AND EASTERN CONTIGUOUS U.S. (CONUS) EARLY IN
WEEK-2. A DEPARTING SURFACE LOW AND ACCOMPANYING FRONTAL SYSTEM INCREASES THE
RISK OF HEAVY SNOWFALL OVER PARTS OF THE MID-ATLANTIC, WITH EPISODES OF HIGH
WINDS ALONG THE EASTERN SEABOARD. UPSTREAM, DEVELOPING MID-LEVEL HIGH PRESSURE
IS EXPECTED TO BRING DRIER CONDITIONS FOR MANY AREAS IN THE WESTERN CONUS.
HAZARDS
HIGH RISK OF MUCH BELOW NORMAL TEMPERATURE FOR PORTIONS OF THE SOUTHERN AND
CENTRAL PLAINS, AND LOWER AND MIDDLE MISSISSIPPI VALLEY, THU, FEB 20.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE CENTRAL AND
SOUTHERN PLAINS, LOWER AND MIDDLE MISSISSIPPI, TENNESSEE AND OHIO VALLEYS,
SOUTHEAST, AND LOWER GREAT LAKES, THU-FRI, FEB 20-21.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF THE CENTRAL AND
EASTERN CONUS, EXCLUDING PARTS OF NEW ENGLAND, THU-SAT, FEB 20-22.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE ROCKIES AND HIGH PLAINS, THU-FRI,
FEB 20-21.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE APPALACHIANS, SOUTHEAST, AND THE
MID-ATLANTIC, THU, FEB 20.
SLIGHT RISK OF HIGH WINDS ALONG THE EASTERN SEABOARD, THU-FRI, FEB 20-21.
POSSIBLE FLOODING FOR THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS, SOUTHEAST,
AND THE APPALACHIANS.
DETAILED SUMMARY
FOR SATURDAY FEBRUARY 15 - WEDNESDAY FEBRUARY 19:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY FEBRUARY 20 - WEDNESDAY FEBRUARY 26: HEADING INTO WEEK-2,
DYNAMICAL MODELS CONTINUE TO FAVOR MEAN SHORTWAVE 500-HPA TROUGHING CENTERED
OVER THE MIDWEST, WHERE THE RESULTANT NORTHWESTERLY FLOW FROM CANADA REMAINS
FAVORED TO BRING A BLAST OF ANOMALOUSLY COLD AIR INTO THE GREAT PLAINS AND
MISSISSIPPI VALLEY LATER NEXT WEEK. SINCE YESTERDAY, A KEY CHANGE EVIDENT IN
BOTH THE GEFS AND ECWMF ENSEMBLES CONCERNS THE DEVELOPMENT OF POSITIVE 500-HPA
HEIGHT DEPARTURES OVERSPREADING THE EASTERN CONUS IN THE WAKE OF THE MEAN
TROUGH AS IT LIFTS OUT OVER THE NORTHEASTERN CONUS A FEW DAYS INTO THE PERIOD.
CONCURRENTLY, THERE IS ALSO A GROWING NUMBER OF ENSEMBLE MEMBERS POINTING TO
ADDITIONAL SHORTWAVE ENERGY UPSTREAM, WHICH COULD BRING A RENEWED RISK OF
WEATHER RELATED HAZARDS LATER IN THE PERIOD. THESE MID-LEVEL FEATURES ALTER THE
HAZARDS PERSPECTIVE A BIT IN THE UPDATED OUTLOOK, AS THESE DEVELOPMENTS HAVE
IMPLICATIONS ON THE DURATION OF THE HAZARDOUS COLD POTENTIALLY IMPACTING MUCH
OF THE CONUS EARLY IN WEEK-2, AS WELL AS THE TIMING AND LOCATION OF HEAVY
PRECIPITATION AND HEAVY SNOW THREATS MAINLY EAST OF THE ROCKIES DURING THE
PERIOD.
BASED ON THE LATEST RAW TEMPERATURE GUIDANCE AND CALIBRATED PROBABILISTIC
EXTREME TOOLS (PETS), A SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES REMAINS
IN EFFECT FOR MUCH OF THE CENTRAL AND EASTERN CONUS, BUT NOW EXPIRES ON DAY 10
(FEB 22), A DAY EARLIER THAN YESTERDAY’S OUTLOOK WHICH ENDED THE HAZARDS ON FEB
23, WHERE RAW ENSEMBLES SHOW AN ABRUPT AND WIDESPREAD WEAKENING OF NEGATIVE
TEMPERATURE DEPARTURES EAST OF THE ROCKIES. EMBEDDED WITHIN THIS BROAD SLIGHT
AREA, A MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES REMAINS ISSUED AND
VALID THROUGH FEB 21. THIS AREA HAS BEEN EXPANDED NORTHWARD INTO THE NORTHERN
PLAINS AND SOUTHWARD INCLUDE ADDITIONAL PARTS OF THE SOUTHERN CONUS GIVEN
INCREASED COLD SIGNALS IN THE PETS, AND WHERE DETERMINISTIC SOLUTIONS FAVOR
APPARENT TEMPERATURES APPROACHING HAZARDS CRITERIA. GIVEN BETTER AGREEMENT
BETWEEN THE GEFS AND ECWMF PETS INDICATING HIGHER CHANCES (>60%) FOR MINIMUM
TEMPERATURES FALLING BELOW THE 10TH CLIMATOLOGICAL PERCENTILE, A HIGH RISK FOR
MUCH BELOW NORMAL TEMPERATURES IS ALSO ADDED IN THE UPDATED OUTLOOK FOR DAY 8
(FEB 20). THE ADDED HIGH RISK AREA IS ALSO SUPPORTED BY THE LATEST NATIONAL
BLEND OF MODELS (NBM) ANALYSIS, WHICH INDICATES SEVERAL LOCATIONS FROM NORTHERN
TEXAS TO SOUTHERN IOWA APPROACHING OR BREAKING EITHER DAYTIME AND NIGHTTIME
RECORD TEMPERATURES BY THE OUTSET OF WEEK-2. VERY LOW WIND CHILL TEMPERATURES
ARE POSSIBLE IN SOME OF THESE HIGHLIGHTED RISK AREAS. WITH MID-LEVEL HEIGHTS
FAVORED TO BUILD IN OVER THE EAST, THIS PART OF THE COUNTRY IS EXPECTED TO SEE
A FASTER MODERATION OF TEMPERATURES AS THE MEAN SURFACE HIGH SHIFTS OFFSHORE,
ALLOWING FOR MORE SOUTHERLY FLOW FROM THE GULF.
IN ADDITION TO THE POTENTIALLY HAZARDOUS COLD, THERE IS BETTER SUPPORT IN THE
ENSEMBLES FOR EPISODES OF HIGH WINDS CONSISTENT WITH BACKDOOR COLD FRONT
ACTIVITY ACROSS NEW MEXICO AND INTO NORTHERN MEXICO. THEREFORE, A CORRESPONDING
AREA IS POSTED WITH A SLIGHT RISK OF HIGH WINDS ACROSS THE ROCKIES AND HIGH
PLAINS FOR FEB 20-21. ANY ELEVATED WINDS REALIZED MAY ENHANCE THE WILDFIRE
THREAT, PARTICULARLY IN THE SOUTHERN PLAINS WHERE DROUGHT CONDITIONS ARE
CURRENTLY BEING REGISTERED.
FARTHER EAST, SURFACE LOW FORMATION AND AN ACCOMPANYING FRONTAL SYSTEM
CONTINUES TO BE FAVORED AHEAD OF THE EXPANDING SURFACE HIGH PRESSURE. BY THE
OUTSET OF WEEK-2, ENSEMBLES NOW SHOW THE MEAN LOW POSITION AND HIGHEST
PRECIPITATION AMOUNTS FOCUSED WELL OFFSHORE, WITH THE ECWMF IN PARTICULAR,
SUBSTANTIALLY BACKING OFF ON THE STRENGTH OF THIS POTENTIAL SYSTEM COMPARED TO
YESTERDAY. AS A RESULT, THE CORRESPONDING SLIGHT AND MODERATE RISKS OF HEAVY
PRECIPITATION POSTED OVER THE SOUTHEASTERN CONUS ARE DISCONTINUED IN THE
UPDATED OUTLOOK. HOWEVER, BOTH THE GEFS AND ECWMF SHOW A FAIR AMOUNT OF
MOISTURE BEING ENTRAINED OVER PARTS OF THE MID-ATLANTIC AND SOUTHEAST,
CONDUCIVE FOR ACCUMULATING AND POSSIBLY HEAVY SNOW ON THE BACKSIDE OF THE
DEPARTING LOW. THEREFORE, A SLIGHT RISK OF HEAVY SNOW IS POSTED FROM THE
CAROLINAS NORTHWARD TO PENNSYLVANIA AND NEW JERSEY FOR FEB 20 WHERE THE RAW
ECMWF FAVORS THE STRONGEST SNOW SIGNALS (ENSEMBLE MEAN > 1 INCH) WITH CONTINUED
SUPPORT FROM DETERMINISTIC SOLUTIONS. THESE SOLUTIONS ALSO POINT TO A MORE
SOUTHERLY STORM TRACK, WITH THE POTENTIAL FOR MIXED PRECIPITATION ACROSS THE
SOUTHERN PERIPHERY OF THE SLIGHT RISK AREA EAST OF THE APPALACHIANS. A MORE
SOUTHERLY STORM TRACK ALSO PRECLUDES THE CONTINUATION OF A SEPARATE SLIGHT RISK
OF HEAVY SNOW OVER THE NORTHEAST, HOWEVER THERE REMAINS SOME SUPPORT FOR
EPISODES OF HIGH WINDS IN THE WAKE OF THE LOW, THUS A CORRESPONDING WIND HAZARD
IS STILL POSTED FOR FEB 20-21.
TIED TO ADDITIONAL SHORTWAVE ENERGY PROPAGATING FROM THE WEST, ENSEMBLES SHOW
RENEWED RETURN FLOW FROM THE GULF WITH INCREASED PRECIPITATION AMOUNTS OVER THE
SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY AND SOUTHEAST STARTING AROUND DAY 10
(FEB 22). HOWEVER, THESE ENSEMBLES LACK A MEAN SURFACE LOW ANALYZED AT THE
SURFACE, AND PETS DEPICT A RATHER WEAK AND LIMITED DISTRIBUTION OF
PROBABILITIES FOR AMOUNTS EXCEEDING THE 85TH PERCENTILE. THEREFORE, NO
CORRESPONDING PRECIPITATION HAZARDS ARE POSTED AT THIS TIME, BUT THIS POTENTIAL
WILL BE MONITORED IN THE UPCOMING OUTLOOKS. NORTH OF THE TENNESSEE VALLEY,
DRIER CONDITIONS ARE PREDOMINATELY FAVORED FOR MUCH OF WEEK-2. AS A RESULT, THE
POSSIBLE FLOODING HAZARD PREVIOUSLY HIGHLIGHTED IS REDUCED IN COVERAGE AND MORE
LIMITED TO THE SOUTH WHERE INCREASED PRECIPITATION IS MOST LIKELY TO RETURN
DURING WEEK-2. WHILE THERE IS A SLIGHT TILT TOWARDS BELOW NORMAL PRECIPITATION
IN TENNESSEE VALLEY, THIS AREA REMAINS VULNERABLE FOR LONG DURATION FLOODING
WHERE ANY ADDITIONAL PRECIPITATION MAY EXACERBATE GROUND CONDITIONS. WITHIN THE
POSSIBLE FLOODING AREA HIGHLIGHTED, MANY LOCATIONS HAVE REGISTERED WELL
ABOVE-NORMAL PRECIPITATION SINCE EARLY FEBRUARY, AND ARE FORECAST TO RECEIVE >3
INCHES, BASED ON WPC WEEK-1 QPF.
UPSTREAM, ENSEMBLES CONTINUE TO FAVOR MID-LEVEL RIDGING ACROSS THE WESTERN
CONUS, REDUCING THE LIKELIHOOD OF CONTINUED ONSHORE FLOW OVER THE WEST COAST.
THERE REMAINS SOME SIGNALS IN THE PRECIPITATION TOOLS FOR NEAR TO ABOVE-NORMAL
PRECIPITATION OVER THE NORTHWESTERN CONUS, WITH INCREASED SNOWFALL AMOUNTS OVER
THE HIGHER ELEVATIONS EARLY IN WEEK-2, HOWEVER THERE IS LESS CONFIDENCE THESE
AMOUNTS WILL EXCEED HAZARD CRITERIA RESULTING IN THE CORRESPONDING HEAVY SNOW
HAZARDS OVER THE CASCADES AND NORTHERN ROCKIES BEING REMOVED IN TODAY’S
OUTLOOK. WITH CONDITIONS FAVORED TO BECOME MUCH DRIER, ESPECIALLY ACROSS
CALIFORNIA, AND FLOW LOOKING TO BECOME MORE OFFSHORE LATER IN WEEK-2, PORTIONS
OF THE WEST MAY SEE RENEWED RISK OF HIGH WINDS. HOWEVER, THERE IS INSUFFICIENT
SUPPORT IN THE TOOLS AT THIS TIME TO ISSUE ANY CORRESPONDING WIND HAZARDS, AND
GIVEN THE ENHANCED PRECIPITATION RECEIVED OVER THE WEST COAST RECENTLY, AND
PRECIPITATION FAVORED DURING WEEK-1, THIS PART OF THE COUNTRY LOOKS TO BE LESS
SUSCEPTIBLE TO ANY WILDFIRE RISK AT THIS TIME.
FOR ALASKA, ENHANCED ONSHORE FLOW IS LIKELY TO PROMOTE ABOVE-NORMAL
PRECIPITATION AND ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE STATE T DURING
WEEK-2. THIS IS REFLECTED IN BOTH THE GEFS AND ECMWF PETS, DEPICTING INCREASED
CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE, THOUGH ACTUAL AMOUNTS
ARE UNSUPPORTIVE TO POST ANY CORRESPONDING HAZARD. HOWEVER, IT SHOULD BE NOTED
THOUGH THAT WARMER TEMPERATURES FAVORED DURING WEEK-2 COULD RESULT IN HIGHER
FREEZING LEVELS (~4000 FT), WHICH COMBINED WITH ANY ENHANCED PRECIPITATION
COULD LEAD TO AN INCREASED RISK OF RUNOFF WITH POSSIBLE LANDSLIDES.
FORECASTER: NICK NOVELLA
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