843
FXUS21 KWNC 121823
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MARCH 12 2025
SYNOPSIS: ON MARCH 20TH, A LOW PRESSURE SYSTEM AND TRAILING COLD FRONT ARE
FORECAST TO TRACK ACROSS THE EASTERN U.S. FROM MARCH 20 TO 22, ENHANCED ONSHORE
FLOW IS EXPECTED TO BRING AN INCREASED RISK OF HEAVY PRECIPITATION, HEAVY
MOUNTAIN SNOW, AND HIGH WINDS TO THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA.
BY MARCH 22 OR 23, MID-LEVEL LOW PRESSURE IS LIKELY TO RESULT IN ANOTHER
SURFACE LOW FORMING ACROSS THE CENTRAL HIGH PLAINS. MID-LEVEL LOW PRESSURE IS
FORECAST OVER THE GULF OF ALASKA THROUGH THE EARLY PART OF WEEK-2 BUT MAY BEGIN
TO WEAKEN BEYOND THAT TIME.
HAZARDS
SLIGHT RISK OF HIGH WINDS FOR THE MIDWEST, NORTHEAST, AND MID-ATLANTIC, THU,
MAR 20.
SLIGHT RISK OF HEAVY PRECIPITATION FOR COASTAL AREAS OF THE PACIFIC NORTHWEST
AND NORTHERN CALIFORNIA, THU-SAT, MAR 20-22.
SLIGHT RISK OF HEAVY SNOW FOR THE CASCADES AND NORTHERN SIERRA NEVADA
MOUNTAINS, THU-SAT, MAR 20-22.
SLIGHT RISK OF HEAVY SNOW FOR NORTHERN ROCKIES AND WASATCH MOUNTAINS, THU-SUN,
MAR 20-23.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE WEST AND HIGH PLAINS, THU-SUN,
MAR 20-23.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE OHIO AND TENNESSEE VALLEYS, SUN-WED,
MAR 23-26.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF SOUTHEASTERN ALASKA, THU-FRI,
MAR 20-21.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF THE SOUTHERN PLAINS
DETAILED SUMMARY
FOR SATURDAY MARCH 15 - WEDNESDAY MARCH 19:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY MARCH 20 - WEDNESDAY MARCH 26: THE GEFS AND ECENS AND THEIR
DETERMINISTIC MODEL RUNS CONTINUE TO DEPICT A LOW PRESSURE SYSTEM AND TRAILING
COLD FRONT CROSSING THE EASTERN CONTIGUOUS U.S. (CONUS) ON MARCH 20TH. BASED ON
THE ENSEMBLE MEMBERS HAVING GENERALLY A 984 TO 988-HPA SURFACE LOW, TRACKING
FROM THE GREAT LAKES TO SOUTHEASTERN CANADA, AND A TIGHT PRESSURE GRADIENT, A
SLIGHT RISK OF HIGH WINDS IS POSTED FOR MUCH OF THE MIDWEST, NORTHEAST, AND
MID-ATLANTIC ON MARCH 20. ANTECEDENT DRYNESS ALONG WITH ANY GUSTY WINDS WOULD
LEAD TO AN INCREASED WILDFIRE RISK FOR PORTIONS OF THE MID-ATLANTIC. THE
MODERATE RISK WAS DISCONTINUED AS THE STRONGEST WINDS ARE EXPECTED TO TIME OFF
AND THE ECENS HAS LESS THAN A 40 PERCENT CHANCE OF WIND SPEEDS OF 20 KNOTS. DUE
TO A LACK OF LOW-LEVEL MOISTURE, HEAVY PRECIPITATION IS UNLIKELY ALONG THE COLD
FRONT.
MULTI-MODEL ENSEMBLE MEAN SOLUTIONS ARE IN GOOD AGREEMENT THAT ENHANCED ONSHORE
FLOW AFFECTS THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA FROM MARCH 20-22.
THE GEFS AND ECENS PROBABILISTIC EXTREMES TOOLS (PETS) SUPPORT A SLIGHT RISK OF
HEAVY PRECIPITATION FOR COASTAL AREAS OF NORTHERN CALIFORNIA, OREGON, AND
WASHINGTON. THERE IS A 20 TO 40 PERCENT CHANCE THAT 3-DAY PRECIPITATION TOOLS
EXCEED 2 INCHES ACROSS THE DESIGNATED SLIGHT RISK OF HEAVY PRECIPITATION. IN
ADDITION TO THE INCREASED RISK OF HEAVY PRECIPITATION, A SLIGHT RISK OF HEAVY
SNOW IS POSTED FOR THE CASCADES AND NORTHERN SIERRA NEVADA MOUNTAINS BASED ON
24-HOUR PRECIPITATION AMOUNTS FROM THE ENSEMBLE MEANS ALONG WITH THE GEFS PET
WHICH HAS A GREATER THAN 20 PERCENT CHANCE THAT 3-DAY SNOW WATER EQUIVALENT
EXCEEDS 1 INCH, LIQUID EQUIVALENT. MODEL GUIDANCE ALSO SUPPORTS A SLIGHT RISK
OF HEAVY SNOW FOR THE NORTHERN ROCKIES AND WASATCH MOUNTAINS THROUGH MARCH 23.
ALTHOUGH THE GEFS AND ECENS DIFFER ON THE AMPLITUDE OF A 500-HPA TROUGH
SHIFTING INLAND FROM THE NORTHEASTERN PACIFIC TO THE WESTERN CONUS EARLY IN
WEEK-2, THE PREDICTED SURFACE AND 500-HPA LONGWAVE PATTERN SUPPORTS A SLIGHT
RISK OF HIGH WINDS FOR A BROAD AREA FROM THE WEST COAST EAST ACROSS THE ROCKIES
TO THE HIGH PLAINS.
ONCE THE 500-HPA TROUGH AXIS SHIFTS EAST TO THE ROCKIES, LEESIDE CYCLOGENESIS
WOULD LIKELY OCCUR ACROSS THE CENTRAL HIGH PLAINS ON MARCH 22 OR 23. RETURN
FLOW FROM THE GULF IS EXPECTED TO PROVIDE ENOUGH LOW-LEVEL MOISTURE AND
INSTABILITY TO INCREASE CHANCES FOR THUNDERSTORMS WITH LOCALLY HEAVY
PRECIPITATION. BASED ON 24-HOUR PRECIPITATION AMOUNTS FROM THE GEFS AND ECENS,
A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED ACROSS THE OHIO AND TENNESSEE
VALLEYS FROM MARCH 23-26. 28-DAY AVERAGE STREAMFLOWS ARE RUNNING AT OR ABOVE
THE 90TH PERCENTILE THROUGHOUT MUCH OF KENTUCKY AND NORTHWESTERN TENNESSEE
WHICH MAKES THOSE AREAS VULNERABLE TO FLOODING. A FLOODING POSSIBLE HAZARD MAY
BE NEEDED FOR PORTIONS OF KENTUCKY AND TENNESSEE IN SUBSEQUENT OUTLOOKS.
A NEGATIVELY-TILTED AND AMPLIFIED 500-HPA TROUGH IS EXPECTED TO AFFECT
SOUTHEASTERN ALASKA AT THE BEGINNING OF WEEK-2. BASED ON THE ECENS PET, A
SLIGHT RISK OF HEAVY PRECIPITATION IS MAINTAINED FOR PORTIONS OF SOUTHEASTERN
ALASKA ON MARCH 22 AND 23. LATER IN WEEK-2, THE GEFS AND ECENS DEPICT A
TRANSITION TOWARDS MORE OF A MEAN 500-HPA RIDGE OVER THE NORTHEASTERN PACIFIC
AND WESTERN NORTH AMERICA.
FORECASTER: BRAD PUGH
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page