911
FXUS21 KWNC 191807
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 19 2023
SYNOPSIS: A CUT-OFF MID-LEVEL LOW IS FORECAST TO DEVELOP ACROSS THE
SOUTHEASTERN U.S. (CONUS) PRIOR TO THE START OF WEEK-2, WITH IMPACTS CONTINUING
INTO THE FORECAST PERIOD. THERE ARE ELEVATED CHANCES OF HEAVY PRECIPITATION
ACROSS PARTS OF THE SOUTHEAST AND SOUTHERN MID-ATLANTIC, WITH POTENTIAL FOR
INCREASED WINDS ALONG THE COAST. WHILE THERE REMAINS CONSIDERABLE UNCERTAINTY
AS TO WHETHER THE HEAVIEST PRECIPITATION WILL REMAIN OFFSHORE OR MOVE FURTHER
INLAND, TODAY’S FORECAST HEDGES MORE AGGRESSIVELY CONSIDERING MEMORIAL DAY
WEEKEND COINCIDES WITH THESE POTENTIAL IMPACTS. ELSEWHERE, ACROSS THE CONUS,
BROAD MID-LEVEL HIGH PRESSURE AND ABOVE-NORMAL TEMPERATURES ARE FORECAST, WHICH
COULD LEAD TO LOCALIZED FLOODING DUE TO SNOW MELT OVER HIGHER ELEVATIONS OF THE
WEST, AS WELL AS WORSENING DROUGHT CONDITIONS ACROSS THE CORN BELT DUE TO
LITTLE PRECIPITATION IN THE FORECAST. IN ALASKA, RIVER-ICE BREAK-UP COULD LEAD
TO FLOODING AND ICE JAMS ALONG MAJOR RIVERS.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR THE COASTAL CAROLINAS, SAT, MAY 27.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHEAST AND SOUTHERN
MID-ATLANTIC, SAT-MON, MAY 27-29.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE GREAT PLAINS AND UPPER
AND MIDDLE MISSISSIPPI VALLEY, SAT, MAY 27.
SLIGHT RISK OF EXCESSIVE HEAT ACROSS PARTS OF THE MIDWEST, SAT-MON, MAY 27-29.
SLIGHT RISK OF HIGH WINDS ALONG THE SOUTHEAST AND MID-ATLANTIC COASTS, SAT, MAY
27.
POSSIBLE FLOODING FOR PORTIONS OF CALIFORNIA, NEVADA, UTAH, WYOMING, WESTERN
MONTANA, IDAHO, OREGON, AND WASHINGTON.
POSSIBLE FLOODING ALONG PORTIONS OF THE JAMES RIVER.
POSSIBLE FLOODING IN PARTS OF WESTERN MAINLAND ALASKA ALONG THE YUKON,
KUSKOKWIM, KOYUKUK, AND KOBUK RIVERS.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF THE EASTERN CORN BELT.
DETAILED SUMMARY
FOR MONDAY MAY 22 - FRIDAY MAY 26:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY MAY 27 - FRIDAY JUNE 02: THERE IS GOOD AGREEMENT IN THE MEAN
WEEK-2 500-HPA HEIGHT HEIGHT FORECASTS ACROSS THE DYNAMICAL MODELS TODAY.
POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST ACROSS MUCH OF THE CONUS, WITH
THE LARGEST POSITIVE ANOMALIES ACROSS THE GREAT LAKES AND NORTHEAST. THIS
FAVORS ABOVE-NORMAL TEMPERATURES ACROSS MANY AREAS, WITH THE ECMWF AND CANADIAN
REFORECAST TOOLS DEPICTING AT LEAST A 40 PERCENT CHANCE MAXIMUM TEMPERATURES
EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE EARLY IN WEEK-2 OVER PARTS OF THE
MIDWEST. ADDITIONALLY, THE UNCALIBRATED GUIDANCE FROM THESE MODELS INDICATES
THE POTENTIAL FOR MAXIMUM TEMPERATURES NEAR OR EXCEEDING 90 DEG F IN SOME
AREAS. THE GEFS IS NOTICEABLY COOLER, WITH MAXIMUM TEMPERATURES GENERALLY
REMAINING IN THE 80S DEG F. HOWEVER, DRY SOILS ARE LIKELY TO PUSH TEMPERATURES
HIGHER. AS A RESULT, A SLIGHT RISK OF EXCESSIVE HEAT IS POSTED ACROSS PARTS OF
THE MIDWEST AND CORN BELT FROM MAY 27-29. LOW RELATIVE HUMIDITY VALUES FAVOR
HEAT INDICES REMAINING UNDER 100 DEG F, WITH THE HEAT HAZARD BASED ON POTENTIAL
ACTUAL HIGH TEMPERATURES (UP TO 10 DEG F ABOVE NORMAL) EARLY IN THE WARM SEASON.
DROUGHT CONCERNS ARE FORECAST TO INCREASE ACROSS PARTS OF THE EASTERN CORN BELT
DURING THE WEEK-2 PERIOD DUE TO THE AFOREMENTIONED WARMTH. SOIL MOISTURE IS
BELOW THE 30TH CLIMATOLOGICAL PERCENTILE OVER SOME AREAS, AND VERY LITTLE
PRECIPITATION IS FORECAST THROUGH WEEK-2. DUE TO THESE FACTORS, A RAPID ONSET
DROUGHT RISK IS HIGHLIGHTED ACROSS PARTS OF THE EASTERN CORN BELT, SPECIFICALLY
SOUTHEASTERN IOWA, CENTRAL ILLINOIS AND INDIANA, AND SOUTHWESTERN OHIO. THERE
ARE ALSO DROUGHT EXPANSION CONCERNS ACROSS THE NORTHERN MID-ATLANTIC, BUT WITH
ADDED UNCERTAINTY DUE TO THE INCREASING ONSHORE FLOW FORECAST EARLY IN WEEK-2
AND THE NORTHWARD EXTENT OF PRECIPITATION.
WARM TEMPERATURES ARE ANTICIPATED TO ENHANCE THE SNOWMELT RATE ACROSS THE
WESTERN CONUS, INDUCING RIVER FLOODING ESPECIALLY ACROSS HIGHER ELEVATIONS IN
THE WEST AND THE SOUTHERN CANADIAN ROCKIES, WHERE A FEW SITES STILL REPORT OVER
50 INCHES OF SNOW WATER CONTENT. THE ABOVE-NORMAL TEMPERATURES MAY CAUSE RAPID
SNOWMELT IN PARTS OF THE SIERRA NEVADA, GREAT BASIN, NORTHERN ROCKIES, AND
PACIFIC NORTHWEST, RESULTING IN AREAS AT HIGH RISK OF FLOODING ALONG MANY
RIVERS, AND IN AREAS ADJACENT TO THE HIGHER ELEVATIONS; HOWEVER, EXPANSIVE,
MULTI-STATE FLOODING IS NOT EXPECTED TO ENVELOP LARGE AREAS OF THE INTERIOR
WEST. FLOODING CONTINUES TO BE POSSIBLE ALONG THE JAMES RIVER IN SOUTH DAKOTA
DUE TO PREVIOUS SNOWMELT.
A CUT-OFF MID-LEVEL LOW IS FORECAST TO DEVELOP ACROSS THE SOUTHEASTERN CONUS
LATE IN WEEK-1 AND PERSIST INTO WEEK-2, LEADING TO UNSETTLED WEATHER DURING
MEMORIAL DAY WEEKEND OVER PARTS OF THE SOUTHEAST AND MID-ATLANTIC. THE ECMWF,
GEFS, AND CANADIAN REFORECAST TOOLS ALL DEPICT AT LEAST A 20 PERCENT CHANCE OF
3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH PERCENTILE AND 1-INCH ACROSS
PARTS OF THESE AREAS, WITH THE ECMWF REFORECAST TOOL CONTINUING TO DEPICT THE
HIGHEST PROBABILITIES (UPWARDS OF 30 PERCENT). A MODERATE RISK OF HEAVY
PRECIPITATION IS POSTED ALONG THE NORTH AND SOUTH CAROLINA COASTS WHERE THE
UNCALIBRATED 0Z ECMWF, GEFS, AND CANADIAN ENSEMBLES DEPICT THE HEAVIEST
PRECIPITATION TOTALS ON DAY-8 (MAY 27), ALTHOUGH THERE REMAINS UNCERTAINTY AS
TO WHETHER OR NOT THE HEAVIEST RAINFALL WILL REMAIN OFFSHORE. A SLIGHT RISK OF
HEAVY PRECIPITATION REMAINS POSTED ACROSS A BROADER AREA EXTENDING FROM THE
EASTERN FLORIDA PENINSULA THROUGH THE SOUTHERN MID-ATLANTIC FROM MAY 27-29.
SOME PRECIPITATION MAY ALSO EXTEND INTO THE NORTHERN MID-ATLANTIC, ALTHOUGH
AMOUNTS ARE EXPECTED TO BE LOWER COMPARED TO FARTHER SOUTH. IN ADDITION TO THE
POTENTIAL RAINFALL, A TIGHT PRESSURE GRADIENT FAVORS INCREASED EASTERLY SURFACE
WINDS ALONG THE COAST, JUSTIFYING A SLIGHT RISK FOR HIGH WINDS ALONG THE COAST
FROM NORTHEASTERN FLORIDA TO SOUTHERN MARYLAND FOR MAY 27. THIS COULD PROMOTE
HEAVY SURF AND RIP CURRENTS ACROSS THE BEACHES.
INCREASED SOUTHERLY SURFACE FLOW ACROSS THE CENTRAL CONUS, COMBINED WITH WEAK
LOW PRESSURE FORECAST ACROSS THE ROCKIES, MAY LEAD TO EPISODES OF HEAVY
PRECIPITATION AND THUNDERSTORMS ACROSS PARTS OF THE GREAT PLAINS AND UPPER AND
MIDDLE MISSISSIPPI VALLEY AT THE OUTSET OF THE PERIOD. WHILE THE SIGNAL IS
WEAKER COMPARED TO THE LATE WEEK-1 TIME FRAME, THE UNCALIBRATED 0Z GEFS, ECMWF,
AND CANADIAN ENSEMBLES DEPICT LINGERING ENHANCED PRECIPITATION TOTALS ACROSS
THE REGION. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION CONTINUES TO BE
HIGHLIGHTED FOR MAY 27. ELEVATED CHANCES OF ABOVE-NORMAL PRECIPITATION ALSO
EXTEND BACK THROUGH THE HIGH PLAINS AND FOUR CORNERS DUE THE RELATIVELY DRIER
CLIMATOLOGY. HOWEVER, 3-DAY PRECIPITATION TOTALS ARE GENERALLY FORECAST TO BE
UNDER A HALF-INCH, PRECLUDING A RELATED HEAVY PRECIPITATION HAZARD FOR THESE
REGIONS.
WEAK MID-LEVEL FLOW ACROSS ALASKA FAVORS ONLY SLIGHT TILTS TOWARD ENHANCED
ABOVE AND BELOW NORMAL TEMPERATURE PROBABILITIES ACROSS PARTS OF NORTHERN AND
SOUTHERN ALASKA RESPECTIVELY. HOWEVER, REGARDLESS OF TEMPERATURES, RIVERS ARE
EXPECTED TO CONTINUE TO RISE ACROSS WESTERN MAINLAND ALASKA DUE TO ICE JAMS,
WHILE THE ICE FRONT HAS GENERALLY PROGRESSED WEST OF FAIRBANKS ALLOWING THE
FLOODING POTENTIAL TO DIMINISH ACROSS EASTERN ALASKA. THERE ARE CURRENTLY
SEVERAL FLOOD WATCHES AND ADVISORIES POSTED THROUGHOUT INTERIOR AND WESTERN
ALASKA. OTHER RIVERS OF CONCERN FOR RIVER ICE BREAK UP LEADING TO THE POTENTIAL
FOR POSSIBLE FLOODING AND ICE JAMS ARE THE KUSKOKWIM, KOYUKUK, AND KOBUK RIVERS.
FORECASTER: THOMAS COLLOW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page