024
FXUS21 KWNC 091809
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 09 2024
SYNOPSIS: MID-LEVEL LOW PRESSURE IS FORECAST TO DEVELOP ACROSS THE WEST-CENTRAL
CONTIGUOUS U.S. (CONUS) LATE IN WEEK-1 AND PERSIST INTO THE FIRST HALF OF
WEEK-2. THIS FAVORS A SERIES OF SURFACE LOWS TRACKING ACROSS THE GREAT PLAINS
TO THE GREAT LAKES. THIS PATTERN COMBINED WITH ENHANCED MOISTURE FLOW FROM THE
GULF OF MEXICO INCREASES THE CHANCES FOR HEAVY PRECIPITATION OVER PARTS OF THE
SOUTHERN PLAINS, MIDDLE AND LOWER MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS,
ALONG WITH POSSIBLE FLOODING ACROSS NORTHEASTERN TEXAS AND THE LOWER
MISSISSIPPI VALLEY. ADDITIONALLY THESE SURFACE LOWS MAY BRING PERIODS OF HEAVY
UPSLOPE SNOW TO PORTIONS OF THE ROCKIES AND HIGH PLAINS DEPENDING ON TRACK AND
COLD AIR AVAILABILITY.
HAZARDS
MODERATE RISK OF HIGH WINDS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL
ROCKIES, NORTHERN AND CENTRAL PLAINS, AND THE UPPER MISSISSIPPI VALLEY, WED,
APR 17.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE INTERIOR WEST AND CENTRAL
CONUS, WED-FRI, APR 17-19.
SLIGHT RISK OF PERIODIC HEAVY PRECIPITATION ACROSS PORTIONS OF THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, WED-SAT, APR 17-20.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES
AND HIGH PLAINS, WED-THU, APR 17-18.
POSSIBLE FLOODING ACROSS PORTIONS OF NORTHEASTERN TEXAS, EXTREME SOUTHEASTERN
OKLAHOMA, AND MUCH OF THE LOWER MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR FRIDAY APRIL 12 - TUESDAY APRIL 16:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY APRIL 17 - TUESDAY APRIL 23: AT THE END OF WEEK-1 AND INTO THE
OUTSET OF WEEK-2, THE 0Z GEFS, ECMWF, AND CANADIAN ENSEMBLES ARE IN GOOD
AGREEMENT REGARDING SURFACE LOW PRESSURE TRACKING FROM THE GREAT PLAINS INTO
THE GREAT LAKES. THIS SYSTEM IS FORECAST TO BRING PERIODS OF HEAVY
PRECIPITATION AND POSSIBLY THUNDERSTORMS TO PORTIONS OF THE SOUTH-CENTRAL
STATES, AND WINTRY WEATHER TO THE NORTHWEST OF THE STORM TRACK OVER THE PARTS
OF THE ROCKIES AND HIGH PLAINS. BEHIND THIS SYSTEM, GUSTY WINDS ARE ALSO
ANTICIPATED ACROSS MUCH OF THE INTERIOR WEST AND CENTRAL CONUS, WITH AN
INCREASED SURFACE PRESSURE GRADIENT IN THE ENSEMBLES SUPPORTING A MODERATE RISK
FOR HIGH WINDS ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES, NORTHERN
AND CENTRAL PLAINS, AND THE UPPER MISSISSIPPI VALLEY ON DAY-8 (APR 17).
AS THIS INITIAL SYSTEM DEPARTS, CONTINUED MID-LEVEL TROUGHING OVER THE
WEST-CENTRAL CONUS FAVORS THE DEVELOPMENT OF ADDITIONAL SURFACE LOW PRESSURE
SYSTEMS OVER THE SAME REGION. A SLIGHT RISK OF HEAVY PRECIPITATION IS
HIGHLIGHTED ACROSS PORTIONS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI, OHIO,
AND TENNESSEE VALLEYS, WED-SAT, APR 17-20 WHERE THE GEFS AND ECMWF
PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT AT LEAST A 20 PERCENT CHANCE OF
3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND
1-INCH. A POSSIBLE FLOOD RISK AREA IS DESIGNATED FOR PARTS OF NORTHEASTERN
TEXAS, EXTREME SOUTHEASTERN OKLAHOMA, AND MUCH OF THE LOWER MISSISSIPPI VALLEY
DUE TO ANTECEDENT WET CONDITIONS ANTICIPATED DURING WEEK-1 AND FORECAST HEAVY
PRECIPITATION DURING WEEK-2, WHERE THERE ARE SOME LOCATIONS ALREADY
EXPERIENCING FLOOD CONDITIONS.
ON THE BACKSIDE OF THESE SYSTEMS, HEAVY SNOW IS POSSIBLE, WITH THE UNCALIBRATED
ECMWF DEPICTING ELEVATED PROBABILITIES FOR SNOWFALL TOTALS UPWARDS OF 6-INCHES
EARLY IN THE PERIOD ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES AND
HIGH PLAINS. THERE IS ALSO SOME SUPPORT FROM THE GEFS SNOW WATER EQUIVALENT
(SWE) PET, WHICH SHOWS SOME OF THESE AREAS HAVING AT LEAST A 20 PERCENT CHANCE
SWE EXCEEDS THE 85TH PERCENTILE AND A HALF-INCH. THEREFORE, A SLIGHT RISK FOR
HEAVY SNOW IS POSTED ACROSS THESE AFOREMENTIONED AREAS FROM APR 17-18,
COINCIDING WITH THE HIGHEST CONFIDENCE BASED ON THE DAILY PATTERN EVOLUTION IN
THE MODELS.
ELEVATED WIND SPEEDS ARE FORECAST ACROSS A LARGE PORTION OF THE INTERIOR WEST
AND CENTRAL CONUS EARLY IN WEEK-2. ALTHOUGH THE HIGHEST CONFIDENCE IS ON DAY-8
(APR 17) RELATED TO THE INITIAL SYSTEM, ANY OTHER SYSTEMS ARE LIKELY TO RESULT
IN SIMILAR HIGH WIND EVENTS. THEREFORE, A BROAD SLIGHT RISK OF HIGH WINDS
REMAINS HIGHLIGHTED ACROSS MUCH OF THESE AREAS THROUGH APR 19, WITH BLIZZARD
CONDITIONS POSSIBLE ACROSS PARTS OF THE ROCKIES AND HIGH PLAINS THAT RECEIVE
SNOWFALL. THE NATIONAL INTERAGENCY FIRE CENTER (NIFC) INDICATES THE GREATEST
POTENTIAL FOR WILDFIRES FOR DAY-7 ACROSS MUCH OF THE GREAT PLAINS AND FOUR
CORNERS, AND THIS SHOULD PERSIST INTO WEEK-2 AS ADDITIONAL SYSTEMS EJECT OUT OF
THE TROUGH.
A PERIOD OF BELOW-NORMAL TEMPERATURES IS POSSIBLE ACROSS PARTS OF THE GREAT
BASIN AND ROCKIES EARLY IN THE PERIOD, WITH SOME SPORADIC AREAS OF MIXED
VEGETATION SUSCEPTIBILITY NOTED ACROSS PARTS OF UTAH AND COLORADO. SUBFREEZING
TEMPERATURES ARE POSSIBLE ACROSS THESE AREAS, BUT THE THREAT OF ANY WIDESPREAD
IMPACTS IS MARGINAL, THUS NO RELATED HAZARD IS POSTED. BY THE MIDDLE OF WEEK-2,
THE ECMWF PET DEPICTS SOME OF THIS ANOMALOUS COLD EXTENDING INTO PARTS OF THE
GREAT PLAINS AND MIDDLE MISSISSIPPI VALLEY, WITH SOME AREAS HAVING AT LEAST A
20 PERCENT CHANCE OF MINIMUM TEMPERATURES FALLING BELOW THE 15TH CLIMATOLOGICAL
PERCENTILE AND 40 DEG F. HOWEVER, THERE IS LITTLE SUPPORT FROM OTHER MODELS OF
TEMPERATURES REACHING THESE THRESHOLDS, PRECLUDING THE ADDITION OF A RELATED
HAZARD.
ACROSS ALASKA, THE WEEK-2 MEAN PATTERN IS PREDICTED TO BE DOMINATED BY POSITIVE
500-HPA HEIGHT ANOMALIES ACROSS MUCH OF THE STATE, WITH INCREASING NORTHERLY
FLOW AND TROUGHING OVER THE ARCTIC FAVORING INCREASED CHANCES FOR NEAR- TO
BELOW-NORMAL TEMPERATURES. SURFACE LOW FORMATION IS POSSIBLE OVER THE GULF OF
ALASKA DURING WEEK-2, ALTHOUGH NOT ANTICIPATED TO SUPPORT WIDESPREAD HAZARDS AT
THIS TIME.
FORECASTER: THOMAS COLLOW
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