940
FXUS21 KWNC 261850
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 26 2026
SYNOPSIS: MID-LEVEL LOW PRESSURE FAVORED OVER THE NORTHEASTERN CONTIGUOUS U.S.
(CONUS), IS EXPECTED TO BRING ANOMALOUSLY COLD AIR AND GUSTY WINDS INTO PARTS
OF THE MIDWEST AND EASTERN U.S. NEXT WEEKEND INTO EARLY NEXT WEEK. WHILE MUCH
OF THE STRONGEST COLD ANOMALIES HAVE TIMED OFF INTO WEEK-1, MUCH BELOW NORMAL
TEMPERATURES WITH FREEZING AND NEAR FREEZING CONDITIONS ARE POSSIBLE IN SOME
AREAS, POTENTIALLY DAMAGING EARLY SPRING BLOOMS. LATER IN WEEK-2, A
RESTRENGTHENING OF MID-LEVEL LOW PRESSURE OVER THE NORTHEASTERN CONUS MAY BRING
THE RETURN OF UNSEASONABLE COLD AIR TO PORTIONS OF THE MIDWEST, BUT THERE IS
TOO MUCH UNCERTAINTY TO POST ANY ADDITIONAL HAZARDS AT THIS TIME.
HAZARDS
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FROM MUCH OF THE EASTERN OHIO
VALLEY, LOWER GREAT LAKES, APPALACHIANS, AND MID-ATLANTIC, MON, MAY 4.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE EASTERN U.S., MON-TUE, MAY 4-5.
DETAILED SUMMARY
FOR WEDNESDAY APRIL 29 - SUNDAY MAY 03:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR MONDAY MAY 04 - SUNDAY MAY 10: BY NEXT WEEKEND, DYNAMICAL MODEL 500-HPA
HEIGHT ANOMALY FORECASTS FAVOR AMPLIFIED TROUGHING OVER THE NORTHEASTERN CONUS,
WITH A STRONG ANOMALOUS RIDGE CENTER TO THE SOUTH OF GREENLAND. THE
PREDOMINANCE OF THESE TWO MID-LEVEL HEIGHT FEATURES OVER NORTH AMERICA WELL
ALIGNS WITH A NEGATIVE NORTH AMERICA OSCILLATION (-NAO) PATTERN, WHICH
DYNAMICALLY (AND HISTORICALLY) SUPPORTS THE ADVECTION OF ANOMALOUS COLD AIR
INTO MANY PARTS OF THE CENTRAL AND EASTERN CONUS. RELATIVE TO YESTERDAY, THE
GEFS AND ECMWF ENSEMBLES HAVE BECOME MUCH MORE VARIED ON THE EVOLUTION OF THE
HEIGHT PATTERN, LEADING TO SIGNIFICANT UNCERTAINTY IN THE UPDATED HAZARD
OUTLOOK. WHILE BOTH MODELS ARE BEGINNING TO FAVOR MORE SOUTHERN STREAM ENERGY
HEADING INTO WEEK-2, THE ECMWF IS STRONGER WITH THE SHORTWAVE ACTIVITY WITH A
BROADER COVERAGE OF NEGATIVE HEIGHT DEPARTURES OVER THE SOUTHERN TIER OF THE
U.S. THAN THE GEFS. THE ECMWF ALSO FEATURES A SUCCINCT NORTHERN STREAM
SHORTWAVE TROUGH OVER SOUTH-CENTRAL CANADA THAT IS VIRTUALLY ABSENT IN THE
GEFS. TAKEN TOGETHER, THIS RESULTS IN THREE MINIMA IN THE ECMWF ENSEMBLE MEAN
ANOMALY HEIGHT FIELD EAST OF THE ROCKIES, WITH A BUSIER SURFACE REFLECTION IN
REGARDS TO POTENTIALLY HAZARDOUS TEMPERATURES AND PRECIPITATION COMPARED TO THE
GEFS EARLY IN WEEK-2. LATER IN THE PERIOD, THE ECWMF HAS BEEN CONSISTENT IN
DEVELOPING AN AMPLIFIED RIDGE OVER SOUTHWESTERN CANADA AND THE NORTHWESTERN
CONUS. ALTHOUGH THE GEFS HAS FALLEN MORE IN LINE IN BUILDING HEIGHTS UPSTREAM
OF THE PERSISTENT TROUGHING OVER THE NORTHEASTERN CONUS, IT PLACES ANOMALOUS
RIDGING OVER THE INTERIOR WEST AND GREAT PLAINS, OUT OF PHASE WITH THE ECMWF.
IN THE WAKE OF A LARGE FRONTAL BOUNDARY LATE IN WEEK-1, SURFACE HIGH PRESSURE
AND ACCOMPANYING ANOMALOUS COLD AIR LOOKS TO BE ESTABLISHED ACROSS PARTS OF THE
CENTRAL AND EASTERN U.S., WITH THE LARGEST NEGATIVE TEMPERATURE DEPARTURES
CENTERED ALONG AN AXIS FROM THE SOUTHERN PLAINS TO THE MID-ATLANTIC. WITH THE
MEAN SURFACE HIGH WEAKENING BY THE OUTSET OF THE PERIOD, A MODERATION OF
TEMPERATURES IS FAVORED AND THE STRONGEST COLD ANOMALIES ARE EXPECTED TO BE
TIMED OFF INTO WEEK-1. THEREFORE, A MODERATE RISK OF MUCH BELOW NORMAL
TEMPERATURES IS DISCONTINUED. HOWEVER, A CORRESPONDING SLIGHT RISK AREA REMAINS
POSTED FOR DAY 8 (MAY 4) OVER PORTIONS OF THE OHIO VALLEY, APPALACHIANS, GREAT
LAKES, AND MID-ATLANTIC WHERE BOTH THE GEFS AND ECMWF PROBABILISTIC EXTREME
TOOLS (PETS) MAINTAIN INCREASED CHANCES FOR MINIMUM TEMPERATURES FALLING BELOW
THE 15TH PERCENTILE AND 40 DEGREES F. ANY RESIDUAL COLD WITH FREEZING OR NEAR
FREEZING TEMPERATURES MAY THREATEN VULNERABLE SPRINGTIME VEGETATION,
PARTICULARLY IN AREAS THAT HAVE EXPERIENCED EARLY GROWTH DUE TO ANTECEDENT
WARMTH DURING APRIL. TIED TO THE AFOREMENTIONED NORTHERN STREAM SHORTWAVE
TROUGH, ECMWF TEMPERATURE TOOLS FAVOR A REEMERGENCE OF ANOMALOUS COLD AIR OVER
THE UPPER MIDWEST, WITH THE PET DEPICTING INCREASED CHANCES FOR MINIMUM
TEMPERATURES FALLING BELOW THE 15TH PERCENTILE OVERSPREADING MUCH OF THE PLAINS
AND MISSISSIPPI VALLEY BY DAY 10 (MAY 6). HOWEVER, THE GEFS MAINTAINS NEAR TO
ABOVE-NORMAL TEMPERATURES FOR THIS PART OF THE COUNTRY, AND THE OPPOSING
TEMPERATURE SIGNALS PRECLUDES ANY ADDITIONAL TEMPERATURE HAZARDS BEING POSTED.
IT SHOULD BE NOTED THAT GIVEN THE FAVORED PERSISTENCE OF A -NAO CIRCULATION TO
PREDOMINATELY KEEP TEMPERATURES BELOW NORMAL MAINLY EAST OF THE MISSISSIPPI
THROUGHOUT WEEK-2, ANY RENEWED COLD SIGNALS WILL CONTINUE TO BE CLOSELY
MONITORED IN THE UPCOMING HAZARD OUTLOOKS.
DESPITE THE SURFACE HIGH WEAKENING OVER THE EASTERN U.S EARLY IN THE PERIOD,
ENSEMBLES CONTINUE TO FAVOR A MEAN SURFACE LOW TO THE SOUTH OF THE CANADIAN
MARITIMES TO POTENTIALLY BRING PERIODS OF HIGH WINDS OVER THE NORTHEASTERN U.S.
WITH THE ECMWF FAVORING STRONGER SOUTHERN STREAM ENERGY ALOFT, ADDITIONAL
SURFACE LOW FORMATION IS FEATURED OFFSHORE OF THE SOUTHEAST. THIS IS A NOVEL
DEVELOPMENT FROM THE ECMWF, AND THOUGH THERE IS MODEST SUPPORT IN THE GEFS FOR
ADDITIONAL SURFACE LOW ACTIVITY IN THE WESTERN ATLANTIC, ELEVATED WIND SPEEDS
NONETHELESS REMAIN POSSIBLE AT THE BASE AND AHEAD OF THE TROUGH AXIS FAVORED
ALOFT. THEREFORE, A SLIGHT RISK OF HIGH WINDS REMAINS ISSUED OVER THE EASTERN
U.S. FOR MAY 4-5 WHERE THERE CONTINUES TO BE INCREASED WIND SIGNALS IN THE
ECMWF PET ALONG WITH INCREASED CHANCES FOR STRONG GUSTS IN THE CALIBRATED
TOOLS. THIS SECONDARY SURFACE LOW IN ECMWF ALSO TRANSLATES INTO HIGHER
PRECIPITATION AMOUNTS FAVORED OVER THE SOUTHEASTERN U.S. LATE IN WEEK-1 AND
INTO EARLY WEEK-2. THE UNCALIBRATED ECMWF SHOWS AT LEAST 20% CHANCES FOR 3-DAY
AMOUNTS EXCEEDING AN INCH FROM THE SOUTHERN PLAINS TO THE LOWER EASTERN
SEABOARD, HOWEVER BOTH THE GEFS AND ECMWF PET ARE CONSIDERABLY MORE LIMITED
WITH ANY HEAVY PRECIPITATION THREAT. GIVEN THIS, AND DIFFERENCES IN THE SURFACE
PATTERN AMONG THESE MODELS, NO PRECIPITATION HAZARDS ARE POSTED.
OVER ALASKA, MODELS CONTINUE TO FAVOR MID-LEVEL TROUGHING OVER THE BERING
STRAIT WITH RIDGING OVER THE MAINLAND. AN ASSOCIATED MEAN SURFACE LOW CENTERED
OVER THE ALEUTIANS IS EXPECTED TO BRING POTENTIALLY STRONG WINDS AND STORMY
CONDITIONS ALONG THE SOUTHERN TIER OF THE STATE EARLY IN WEEK-2 BEFORE THE
PATTERN ALOFT DEAMPLIFIES. CONDITIONS ARE EXPECTED TO REMAIN BELOW HAZARD
THRESHOLDS, AND NO CORRESPONDING WIND OR PRECIPITATION SHAPES ARE POSTED.
ADDITIONALLY, THE TYPICAL PEAK OF THE RIVER ICE BREAKUP SEASON IS APPROACHING,
AND ICE JAM FLOODING CAN OCCUR THIS TIME OF YEAR WITH LITTLE OR NO NOTICE AS
CONDITIONS ON FROZEN RIVERS CAN CHANGE QUICKLY. PLEASE CHECK WITH THE ALASKA
PACIFIC RIVER FORECAST CENTER FOR THE LATEST CONDITIONS AND ADVISORIES.
FORECASTER: NICK NOVELLA
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