884
FXUS21 KWNC 061905
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST MARCH 06 2024
SYNOPSIS: MID-LEVEL LOW PRESSURE INITIALLY FORECAST OVER THE GREAT PLAINS IS
PREDICTED TO SHIFT TO THE NORTHEASTERN U.S. LATER IN WEEK-2, WHILE INCREASING
IN AMPLITUDE. THIS FEATURE IS LIKELY TO RESULT IN ENHANCED CHANCES FOR HEAVY
PRECIPITATION AND THUNDERSTORMS ACROSS THE SOUTH-CENTRAL AND SOUTHEASTERN
STATES EARLY IN WEEK-2, ALONG WITH HEAVY SNOW ACROSS PORTIONS OF THE ROCKIES.
AS THE ASSOCIATED COLD FRONT PROGRESSES OFF THE ATLANTIC COAST, ELEVATED WIND
SPEEDS ALONG WITH RELATIVELY COOLER TEMPERATURES ARE FAVORED TO BUILD INTO THE
EAST DURING THE SECOND HALF OF THE PERIOD. STRONG ONSHORE FLOW FAVORS HEAVY
PRECIPITATION ACROSS SOUTHEAST ALASKA AT THE OUTSET OF THE PERIOD, WITH
BUILDING MID-LEVEL HIGH PRESSURE FORECAST TO LEAD TO RELATIVELY DRIER
CONDITIONS BY THE MIDDLE OF WEEK-2.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN PLAINS, LOWER
MISSISSIPPI VALLEY, AND SOUTHEAST, THU-FRI, MAR 14-15.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE SOUTH-CENTRAL AND
SOUTHEASTERN CONUS, THU-SAT, MAR 14-16.
SLIGHT RISK OF HEAVY SNOW FOR HIGHER ELEVATIONS OF THE ROCKIES AND ADJACENT
AREAS OF THE HIGH PLAINS, THU-FRI, MAR 14-15.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE FOUR CORNERS REGION, GREAT
PLAINS, AND MIDDLE MISSISSIPPI VALLEY, THU-SAT, MAR 14-16.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE NORTHERN PLAINS, UPPER AND
MIDDLE MISSISSIPPI VALLEY, GREAT LAKES, OHIO VALLEY, MID-ATLANTIC, AND
NORTHEAST, SAT-TUE, MAR 16-19.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS SOUTHEAST ALASKA, THU-FRI, MAR 14-15.
SLIGHT RISK OF HIGH WINDS ACROSS SOUTHEAST ALASKA, THU-FRI, MAR 14-15.
POSSIBLE FLOODING FOR PARTS OF THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS,
SOUTHEAST, AND SOUTHERN APPALACHIANS.
DETAILED SUMMARY
FOR SATURDAY MARCH 09 - WEDNESDAY MARCH 13:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY MARCH 14 - WEDNESDAY MARCH 20: THERE IS GOOD AGREEMENT AMONG THE
0Z GEFS, ECMWF, AND CANADIAN ENSEMBLES IN REGARDS TO MID-LEVEL TROUGHING ACROSS
THE ROCKIES AND HIGH PLAINS AT THE OUTSET OF THE PERIOD. A SLIGHT RISK OF HEAVY
SNOW CONTINUES FOR HIGHER ELEVATIONS OF THE ROCKIES AND ADJACENT AREAS OF THE
HIGH PLAINS, MAR 14-15, WHERE THE GEFS PROBABILISTIC EXTREMES TOOL (PET) SHOWS
AT LEAST A 20 PERCENT CHANCE OF 3-DAY LIQUID EQUIVALENT PRECIPITATION EXCEEDING
THE 85TH CLIMATOLOGICAL PERCENTILE AND HALF AN INCH (1-INCH LOCALLY). THE
UNCALIBRATED ECMWF ENSEMBLE SHOWS THE POTENTIAL OF AREAS RECEIVING 4 TO 6
INCHES OF SNOW DURING THIS TIMEFRAME (GREATEST TOTALS EXCEEDING 6 INCHES ACROSS
THE CENTRAL ROCKIES) FURTHER SUPPORTING THE HAZARD.
THE AFOREMENTIONED TROUGH IS FORECAST TO GRADUALLY SHIFT EASTWARD AND IMPACT
WEATHER ACROSS MUCH OF THE EASTERN HALF OF THE CONTIGUOUS U.S. (CONUS)
THROUGHOUT WEEK-2. MODELS INDICATE AN AREA OF SURFACE LOW PRESSURE TRACKING
NORTHWARD ACROSS THE MISSISSIPPI VALLEY AND GREAT LAKES EARLY IN THE PERIOD,
WITH A TRAILING COLD FRONT PROGRESSING THROUGH THE EAST. HEAVY PRECIPITATION
AND POSSIBLY THUNDERSTORMS ARE FORECAST ACROSS PORTIONS OF THE SOUTH-CENTRAL
AND SOUTHEASTERN STATES. WHILE THE GEFS AND ECMWF PETS GENERALLY DEPICT
PROBABILITIES OF 20-40 PERCENT FOR 3-DAY PRECIPITATION TOTALS EXCEEDING THE
85TH CLIMATOLOGICAL PERCENTILE OR 1-INCH, THE UNCALIBRATED GUIDANCE IS MORE
ROBUST OVER THESE AREAS, AND FOCUSED MORE WESTWARD COMPARED TO YESTERDAY. THE
0Z ECMWF ENSEMBLE INDICATES PROBABILITIES ABOVE 40 PERCENT ACROSS PARTS OF THE
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY FOR 3-DAY PRECIPITATION TOTALS
EXCEEDING 2-INCHES, WITH 24-HOUR TOTALS EXCEEDING THREE QUARTERS OF AN INCH IN
THE 0Z ECMWF AND GEFS ENSEMBLE MEANS OVER SOME AREAS. GIVEN THESE SIGNALS, AND
ALSO THE FAVORABLE SET-UP FOR CONVECTION WHICH COULD FAVOR HIGHER PRECIPITATION
AMOUNTS LOCALLY, A MODERATE RISK OF HEAVY PRECIPITATION IS HIGHLIGHTED ACROSS
PORTIONS OF THE SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST, MAR
14-15, WITH A MORE EXPANSIVE SLIGHT RISK THAT EXTENDS NORTHWARD INTO THE MIDDLE
MISSISSIPPI VALLEY, SOUTHERN APPALACHIANS, AND SOUTHERN MID-ATLANTIC THROUGH
MAR 16. ALTHOUGH THE FRONTAL PASSAGE IS LIKELY TO BRING ENHANCED PRECIPITATION
CHANCES TO THE ENTIRE EASTERN SEABOARD BY THE MIDDLE OF THE PERIOD, THE PETS
AND UNCALIBRATED TOOLS KEEP THE HIGHEST PRECIPITATION TOTALS TO THE SOUTH, WITH
LESS CONFIDENCE ON REACHING HAZARDS CRITERIA ACROSS THE NORTHERN MID-ATLANTIC
AND NORTHEAST PRECLUDING AN EXPANSION OF THE PRECIPITATION HAZARD. ANTECEDENT
HEAVY PRECIPITATION PREDICTED DURING WEEK-1 ACCORDING TO THE WEATHER PREDICTION
CENTER’S (WPC) COMBINED WITH EXPECTED HEAVY WEEK-2 PRECIPITATION SUPPORTS A
POSSIBLE FLOOD RISK FOR PORTIONS OF THE SOUTHEASTERN CONUS.
ELEVATED WIND SPEEDS ARE FORECAST TO ACCOMPANY THIS SYSTEM AS WELL. INITIALLY
THE STRONGEST WINDS ARE FAVORED ACROSS THE FOUR CORNERS AND GREAT PLAINS,
CO-LOCATED WITH THE FORECAST TROUGH AXIS POSITIONING AT THE OUTSET OF THE
PERIOD. GUSTY WINDS MAY EXACERBATE WILDFIRE RISK WHERE THERE ARE ALREADY
ONGOING WILDFIRES, ESPECIALLY IN THE TEXAS PANHANDLE WHERE THERE IS A LARGE
FIRE IN THE SMOKEHOUSE CREEK AREA THAT IS ONLY 44% CONTAINED. THEREFORE, A
SLIGHT RISK FOR HIGH WINDS REMAINS IN PLACE FOR THESE AREAS, MAR 14-16. AS THE
TROUGH AND ASSOCIATED FRONTAL SYSTEM PROGRESS EASTWARD, THE STRONGEST WIND
SIGNALS ARE FORECAST TO SHIFT TOWARD THE MIDWEST AND NORTHEAST BY THE MIDDLE OF
WEEK-2. THIS IS EVIDENCED BY AN INCREASING PRESSURE GRADIENT ACROSS THE MIDWEST
THROUGH THE EAST COAST, AND IN THE ECMWF PET, WHICH DEPICTS PROBABILITIES OF AT
LEAST 20 PERCENT FOR WIND SPEEDS REACHING THE 85TH CLIMATOLOGICAL PERCENTILE
AND 20-MPH OVER SOME AREAS. THEREFORE, ANOTHER SLIGHT RISK OF HIGH WINDS HAZARD
IS HIGHLIGHTED ACROSS PORTIONS OF THE NORTHERN PLAINS, UPPER AND MIDDLE
MISSISSIPPI VALLEY, GREAT LAKES, OHIO VALLEY, MID-ATLANTIC, AND NORTHEAST, MAR
16-19. THE INCREASED NORTHERLY FLOW MAY ALSO BEGIN TO USHER IN RELATIVELY
COOLER TEMPERATURES ACROSS THE EASTERN HALF OF THE CONUS TOWARD THE END OF
WEEK-2, WITH THE POTENTIAL NEGATIVE ARCTIC OSCILLATION AND MJO PROGRESSION
FAVORING THIS COOLER PATTERN INTO LATE MARCH. WHILE NO TEMPERATURE HAZARDS ARE
DEPICTED, ONGOING WARM CONDITIONS ARE LEADING TO INCREASING VEGETATION GREEN-UP
ACROSS PARTS OF THE EAST, AND A FLIP TO A COOLER PATTERN COULD LEAD TO ADVERSE
VEGETATION IMPACTS DEPENDING ON THE EXPANSE OF SUSCEPTIBLE VEGETATION AND THE
MAGNITUDE OF THE COLD.
FOR ALASKA, THERE IS GOOD MODEL AGREEMENT INDICATING A TRANSITION IN THE
MID-LEVEL HEIGHT PATTERN FROM TROUGHING ACROSS THE STATE AT THE ONSET OF WEEK-2
TO RIDGING LATER IN WEEK-2. MULTIPLE MODEL ENSEMBLE MEANS SHOW THE POTENTIAL
FOR STRONG ONSHORE FLOW INTO SOUTHEAST ALASKA AT THE BEGINNING OF WEEK-2 DUE TO
THE PREDICTED STRONG PRESSURE GRADIENT ASSOCIATED WITH THE AFOREMENTIONED
PATTERN TRANSITION. THE GEFS PET INDICATES AT LEAST A 20 PERCENT CHANCE OF
3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND
1-INCH (2-INCHES IN THE ECMWF PET) OVER SOME AREAS. MUCH OF THIS IS
CONCENTRATED ON DAY-8 (MAR 14), POSSIBLY LINGERING INTO DAY-9 (MAR 15) BASED ON
24-HOUR DAILY ENSEMBLE MEANS. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION
IS HIGHLIGHTED ACROSS SOUTHEAST ALASKA, MAR 14-15, ALONG WITH A SLIGHT RISK OF
HIGH WINDS FOR THE SAME TIME FRAME DUE TO THE PREDICTED STRONG PRESSURE
GRADIENT, AS WELL AS ADDITIONAL SUPPORT FROM THE ECMWF PET. A RELATIVELY DRIER
PATTERN IS FAVORED ACROSS THIS REGION BY THE MIDDLE OF WEEK-2 AS RIDGING
BECOMES MORE DOMINANT.
FORECASTER: THOMAS COLLOW
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