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FXUS21 KWNC 221926
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 22 2023
SYNOPSIS: THE SYNOPTIC PATTERN DURING THE WEEK-2 PERIOD IS CHARACTERIZED BY
WIDESPREAD MID-LEVEL HIGH PRESSURE OVER CANADA AND WEAK LOW PRESSURE ALONG BOTH
COASTS OF NORTH AMERICA. THIS RESULTS IN MOSTLY WARMER, QUIETER WEATHER FOR
MOST OF THE CONTIGUOUS U.S. (CONUS). A FAVORABLE ENVIRONMENT FOR THUNDERSTORMS
TYPICAL FOR THIS TIME OF YEAR OVER THE CENTRAL PLAINS MAY RESULT IN POTENTIALLY
IMPACTFUL PRECIPITATION. THE POTENTIAL FOR RIVER FLOODING RELATED TO THE SPRING
THAW CONTINUES FOR MUCH OF THE WEST AND PORTIONS OF ALASKA, AS WELL AS ALONG
THE JAMES RIVER IN SOUTH DAKOTA.
HAZARDS
SLIGHT RISK FOR HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN AND CENTRAL
PLAINS, TUE-SAT, MAY 30-JUN 3.
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 MIDDLE MISSISSIPPI AND OHIO
VALLEYS.
DETAILED SUMMARY
FOR THURSDAY MAY 25 - MONDAY MAY 29:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY MAY 30 - MONDAY JUNE 05: THE WEEK-2 SYNOPTIC PICTURE AS DEPICTED BY
ENSEMBLE MODEL SOLUTIONS FOR 500-HPA HEIGHT ANOMALIES RESEMBLES AN OMEGA BLOCK
WITH WEAK TROUGHING ALONG BOTH COASTS OF NORTH AMERICA AND EXPANSIVE RIDGING
OVER MUCH OF CANADA. THIS FEATURE ENDURES THROUGHOUT THE FORECAST PERIOD AND
RESULTS IN WARMER BUT RELATIVELY QUIET WEATHER FOR MUCH OF THE CONUS. ONE
EXCEPTION TO THIS IS OVER THE GREAT PLAINS, WHERE INCREASED LOW-LEVEL JET
ACTIVITY FAVORS INCREASED PROBABILITIES OF HEAVY PRECIPITATION WITH PERIODIC
THUNDERSTORMS FOR THE REGION. REFORECAST TOOLS FROM THE GEFS, ECMWF, AND CMCE
ALL INDICATE AT LEAST A 20% PROBABILITY OF EXCEEDING THE 85TH PERCENTILE AND 1
INCH FOR 3-DAY PRECIPITATION OVER PORTIONS OF THE GREAT PLAINS, THEREFORE A
SLIGHT RISK FOR HEAVY PRECIPITATION IS POSTED FOR THE REGION. THE GEFS ALSO
INDICATES EXCEEDING THE AFOREMENTIONED THRESHOLDS FOR MUCH OF THE GULF COAST,
BUT NO ACCOMPANYING HAZARD IS POSTED DUE TO LACK OF SUPPORT FROM THE OTHER
ENSEMBLES.
EXPANSIVE RIDGING OVER MUCH OF CENTRAL NORTH AMERICA IS LIKELY TO RESULT IN
WARMER TEMPERATURES, PARTICULARLY FOR THE NORTH-CENTRAL CONUS. THE REFORECAST
TOOLS ALL INDICATE A 20% OF EXCEEDING THE 85TH PERCENTILE FOR MAXIMUM
TEMPERATURES FOR THIS REGION FROM MAY 30 THROUGH AT LEAST JUNE 3, BUT DUE TO AN
ANTICIPATED DRY AIR MASS WITH LOW HUMIDITY, IMPACTS FROM THESE WARM
TEMPERATURES ARE NOT LIKELY TO EXCEED HAZARD THRESHOLDS SO NO HAZARD IS POSTED
AT THIS TIME.
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.
WARMING 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 SATURATING GROUND CONDITIONS.
WEAK MID-LEVEL FLOW ACROSS ALASKA FAVORS ONLY A SLIGHT TILT TOWARD 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: DANNY BARANDIARAN
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