685
FXUS21 KWNC 271808
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT APRIL 27 2023
SYNOPSIS: MID-LEVEL LOW PRESSURE IS FORECAST TO BE CENTERED ALONG OR NEAR THE
EAST AND WEST COASTS DURING EARLY MAY, WHILE MID-LEVEL HIGH PRESSURE BECOMES
ESTABLISHED OVER THE NORTH-CENTRAL U.S. ALTHOUGH MID-LEVEL LOW PRESSURE FAVORS
ABOVE-NORMAL PRECIPITATION THROUGHOUT THE WEST AND RIO GRANDE VALLEY, HEAVY
PRECIPITATION IS NOT ANTICIPATED. COOLER-THAN-NORMAL TEMPERATURES ARE FORECAST
TO PERSIST ACROSS MUCH OF THE EASTERN U.S. THROUGH EARLY MAY. SPRINGTIME
FLOODING, ASSOCIATED WITH SNOWMELT, IS LIKELY TO PERSIST ACROSS PARTS OF THE
WEST ALONG WITH THE RED RIVER OF THE NORTH, JAMES RIVER, AND UPPER TO MIDDLE
MISSISSIPPI RIVER. SURFACE HIGH PRESSURE TO THE NORTHEAST OF ALASKA FAVORS NEAR
TO BELOW-NORMAL TEMPERATURES FOR ALASKA.
HAZARDS
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE EASTERN CORN BELT, UPPER
OHIO VALLEY, AND CENTRAL TO SOUTHERN APPALACHIANS, FRI-TUE, MAY 5-9.
POSSIBLE FLOODING FOR PORTIONS OF CALIFORNIA, IDAHO, NEVADA, AND UTAH.
POSSIBLE FLOODING ALONG PORTIONS OF THE RED RIVER OF THE NORTH, JAMES RIVER,
MISSISSIPPI RIVER, AND THE MINNESOTA RIVER.
DETAILED SUMMARY
FOR SUNDAY APRIL 30 - THURSDAY MAY 04:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY MAY 05 - THURSDAY MAY 11: THE RECENT WARMUP ACROSS THE WEST HAS LED
TO MORE SNOWMELT, ELEVATED FLOWS ALONG STREAMS AND RIVERS, AND INCREASED THE
FLOODING RISK FOR PARTS OF CALIFORNIA, NEVADA, SOUTHEASTERN IDAHO, AND UTAH.
THE POSSIBLE FLOODING AREA CONTINUES FOR PORTIONS OF THE WEST SINCE THIS
FLOODING RISK IS ANTICIPATED TO PERSIST WELL INTO MAY. BASED ON THE LATEST
MODEL GUIDANCE, THE HEAVIEST SNOWFALL ACROSS THE SIERRA NEVADA MOUNTAINS IS
FORECAST TO OCCUR PRIOR TO WEEK-2. ALTHOUGH THE HEAVY SNOW HAZARD IS
DISCONTINUED TODAY, THE NEARBY LONGWAVE TROUGH COULD BRING ACCUMULATING
SNOWFALL TO THE SIERRAS DURING EARLY MAY.
SINCE LEVELS ALONG THE RED RIVER OF THE NORTH AT AND TO THE SOUTH OF GRAND
FORKS, NORTH DAKOTA ARE FORECAST TO DECREASE FROM MODERATE TO MINOR FLOOD
STAGE, THE SOUTHERN EXTENT OF THE POSSIBLE FLOODING SHAPE WAS REDUCED. POSSIBLE
FLOODING REMAINS TO THE NORTH OF GRAND FORKS ALONG WITH THE JAMES RIVER IN
SOUTH DAKOTA. MODERATE TO MAJOR FLOODING IS FORECAST TO PERSIST WELL INTO MAY
ALONG THE UPPER TO MIDDLE MISSISSIPPI RIVER.
THE GEFS AND ECMWF ENSEMBLE MEANS DEPICT A PERSISTENT LONGWAVE TROUGH NEAR THE
EAST COAST INTO THE SECOND WEEK OF MAY WHICH IS LIKELY TO DELAY ANY SIGNIFICANT
WARMING TREND EAST OF THE MISSISSIPPI RIVER. A SLIGHT RISK OF MUCH BELOW-NORMAL
TEMPERATURES (MAY 5-9) IS MAINTAINED FOR PARTS OF THE EAST-CENTRAL U.S. WHERE
THE GEFS AND ECMWF REFORECAST TOOLS DEPICT MINIMUM TEMPERATURES HAVING AT LEAST
A 20% CHANCE OF FALLING BELOW THE 15TH PERCENTILE AND 40 DEGREES F.
30-DAY PRECIPITATION DEFICITS EXCEED 2 INCHES ACROSS MUCH OF MISSOURI,
SOUTHEASTERN IOWA, AND PARTS OF CENTRAL ILLINOIS. AS TEMPERATURES SEASONALLY
WARM AND EVAPOTRANSPIRATION RATES INCREASE LATER NEXT MONTH, THESE ANTECEDENT
DRY AREAS WILL BE VULNERABLE TO RAPID ONSET OF DROUGHT. GIVEN THE LIKELIHOOD
FOR BELOW-NORMAL PRECIPITATION DURING THE NEXT TWO WEEKS, A RAPID ONSET DROUGHT
HAZARD MAY BE NECESSARY FOR THIS REGION IN SUBSEQUENT OUTLOOKS.
FORECASTER: BRAD PUGH
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