456
FXUS21 KWNC 251947
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 25 2023
SYNOPSIS: THE SYNOPTIC PATTERN DURING THE WEEK-2 PERIOD IS CHARACTERIZED BY
WIDESPREAD MID-LEVEL HIGH PRESSURE OVER CANADA AND WEAK MID-LEVEL LOW PRESSURE
ALONG BOTH COASTS OF NORTH AMERICA. THIS RESULTS IN WARMER, QUIETER WEATHER FOR
MOST OF THE CONTIGUOUS U.S. (CONUS). ENHANCED CHANCES FOR EXCESSIVE HEAT IN
PARTS OF THE MIDWEST ARE ANTICIPATED TO WANE EARLY WEEK-2, BUT AS THE ANOMALOUS
MID-LEVEL RIDGE IN CANADA DRIFTS WEST, THERE WILL BE SLIGHTLY ENHANCED CHANCES
FOR A PERIOD OF NOMINALLY-EXCESSIVE HEAT IN THE NORTHWEST CONUS LATER IN THE
PERIOD. A FAVORABLE ENVIRONMENT FOR THUNDERSTORMS IN THE CENTRAL AND SOUTHERN
PLAINS AND ADJACENT PARTS OF THE CENTRAL ROCKIES MAY RESULT IN POTENTIALLY
IMPACTFUL PRECIPITATION THROUGH THE MIDDLE OF WEEK-2. THE POTENTIAL FOR RIVER
FLOODING MOSTLY RELATED TO THE SPRING THAW CONTINUES FOR PORTIONS OF THE WEST
CONUS, ALASKA, AND ALONG PORTIONS OF THE JAMES RIVER IN SOUTH DAKOTA AND SOURIS
RIVER IN NORTH DAKOTA.
HAZARDS
MODERATE RISK FOR HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN PLAINS, FRI,
JUN 2.
SLIGHT RISK FOR HEAVY PRECIPITATION FOR PORTIONS OF THE PLAINS AND ADJACENT
ROCKIES, FRI-MON, JUN 2-5.
SLIGHT RISK FOR EXCESSIVE HEAT FOR PORTIONS OF THE UPPER MIDWEST, AND THE OHIO,
MIDDLE AND UPPER MISSISSIPPI VALLEYS, FRI-SAT, JUN 2-3.
SLIGHT RISK FOR EXCESSIVE HEAT FOR PARTS OF THE NORTHWEST SUN-THU, JUN 4-8.
POSSIBLE FLOODING FOR PORTIONS OF CALIFORNIA, NEVADA, UTAH, WYOMING,
SOUTHWESTERN MONTANA, AND IDAHO.
POSSIBLE FLOODING ALONG PORTIONS OF THE JAMES RIVER IN SOUTH DAKOTA.
POSSIBLE FLOODING ALONG PORTIONS OF THE SOURIS RIVER IN NORTH DAKOTA.
POSSIBLE FLOODING IN PARTS OF WESTERN MAINLAND ALASKA, ALONG THE YUKON,
KUSKOKWIM, KOYUKUK, AND KOBUK RIVERS.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF THE UPPER MIDWEST, AND THE MIDDLE
MISSISSIPPI AND OHIO VALLEYS.
DETAILED SUMMARY
FOR SUNDAY MAY 28 - THURSDAY JUNE 01:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JUNE 02 - THURSDAY JUNE 08: 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, SLIGHTLY
BELOW-NORMAL MID-LEVEL 500-HPA HEIGHTS ALONG THE SOUTHERN TIER OF THE CONUS,
AND EXPANSIVE MID-LEVEL RIDGING OVER MUCH OF CANADA. THIS GENERAL CONFIGURATION
CONTINUES THROUGH THE PERIOD, ALTHOUGH THE ANOMALOUS MID-LEVEL RIDGE CENTERED
OVER CANADA IS EXPECTED TO SLOWLY RETROGRESS TOWARD WESTERN CANADA AND WEAKEN
SLIGHTLY AS THE PERIOD PROGRESSES. AS A RESULT, WARM AND GENERALLY QUIET
WEATHER IS PREDICTED TO PREVAIL ACROSS THE CONUS. ONE EXCEPTION TO THIS IS OVER
PART OF THE GREAT PLAINS AND ADJACENT ROCKIES, WHERE INCREASED LOW-LEVEL JET
(LLJ) ACTIVITY CREATES ENHANCED PROBABILITIES OF HEAVY PRECIPITATION WITH
PERIODIC THUNDERSTORMS FOR THE REGION THROUGH THE MIDDLE OF WEEK-2. REFORECAST
TOOLS FROM THE GEFS, ECMWF, AND CMCE ALL INDICATE AT LEAST A 20% PROBABILITY OF
EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND 1 INCH FOR 3-DAY ACCUMULATED
PRECIPITATION OVER PORTIONS OF THE GREAT PLAINS AND ADJACENT ROCKIES,
SUPPORTING A SLIGHT RISK OF HEAVY PRECIPITATION ACROSS THE REGION, JUN 1-5.
THIS SLIGHT RISK AREA EXTENDS FARTHER NORTH THAN YESTERDAY BASED ON RAW OUTPUT
FROM THE CMCE AND ECMWF ENSEMBLE MEANS FOR THE FIRST HALF OF WEEK-2.
ADDITIONALLY, THE ECMWF REFORECAST TOOL INDICATES AT LEAST A 40% PROBABILITY OF
EXCEEDING THE 85TH PERCENTILE FOR PORTIONS OF THE SOUTHERN PLAINS ON DAY 8 (FRI
JUN 2). THE GEFS REFORECAST TOOL IS NOT AS BULLISH BUT DOES INDICATE
PROBABILITIES OVER 30% FOR EARLY WEEK-2. GIVEN THESE ENHANCED PROBABILITIES,
THE CONSISTENCY OF THE SIGNAL FOR SEVERAL DAYS, AND GOOD INDICATIONS FROM
MULTIPLE MODELS OF AN ENHANCED LLJ EARLY IN WEEK-2, A MODERATE RISK FOR HEAVY
PRECIPITATION IS POSTED FOR THE TEXAS PANHANDLE AND ADJACENT AREAS FOR JUN 2.
EXPANSIVE MID-LEVEL RIDGING OVER MUCH OF CENTRAL NORTH AMERICA IS LIKELY TO
RESULT IN WARMER TEMPERATURES, PARTICULARLY FOR THE NORTHERN HALF OF THE CONUS.
ALL REFORECAST TOOLS INDICATE AT LEAST A 20% CHANCE OF MAXIMUM TEMPERATURE
EXCEEDING THE 85TH DURING JUN 2-3 FROM THE NORTHWESTERN OHIO VALLEY THROUGH THE
MIDDLE AND UPPER MISSISSIPPI VALLEYS AND THE SOUTHWESTERN GREAT LAKES REGION.
THE ECMWF REFORECAST TOOL AND TO A LESSER EXTENT THE CMCE COUNTERPART FAVORS A
WARMER SOLUTION WITH 30% TO 50% PROBABILITIES OF EXCEEDING THE 85TH PERCENTILE,
BUT GEFS-BASED TOOLS BRING IN SIGNIFICANT UNCERTAINTY, PRECLUDING DESIGNATING
ANY AREAS WITH A MODERATE RISK OF EXCESSIVE HEAT. DEW POINTS AND ASSOCIATED
HEAT INDICES ARE NOT EXPECTED TO BE EXTREMELY ELEVATED, BUT NONETHELESS THERE
IS THE POTENTIAL FOR TEMPERATURES TO EXCEED 90 DEG F FOR PORTIONS OF THE UPPER
MIDWEST FOR THE FIRST TIME THIS SEASON. THE PAST ONE TO TWO MONTHS HAVE BEEN
DRIER THAN NORMAL IN THIS REGION, WHICH INCREASES THE ODDS FOR HIGHER
TEMPERATURES BUT LIMITS THE POTENTIAL FOR UNUSUALLY HIGH DEW POINTS. TAKING ALL
OF THIS INTO CONSIDERATION, A SLIGHT RISK OF EXCESSIVE HEAT IS POSTED FROM
WESTERN INDIANA WESTWARD THROUGH NORTHERN MISSOURI AND NORTHWARD ACROSS
SOUTHERN MINNESOTA, INCLUDING PART OF THE CHICAGO METRO AREA, JUN 2-3. LATER IN
THE FORECAST PERIOD, MODEL ENSEMBLES ALL DEPICT A RETROGRESSION AND SLOW
DE-AMPLIFICATION OF THE EXPANSIVE RIDGE OVER CANADA, WHICH COULD BRING MUCH
ABOVE-NORMAL TEMPERATURES TO THE NORTHWESTERN CONUS TOWARDS THE MIDDLE AND END
OF WEEK-2. THERE IS STILL A LOT OF UNCERTAINTY WITH REGARD TO THIS POTENTIAL
FOR HAZARDOUS HEAT, BUT THERE ARE ENOUGH INDICATORS SHOWING THIS POTENTIAL TO
POST A SLIGHT RISK FOR EXCESSIVE HEAT OVER THE NORTHWEST FOR DAYS 10-14 (JUN
4-8).
DROUGHT CONCERNS ARE FORECAST TO INCREASE ACROSS PARTS OF THE CENTRAL AND
EASTERN CORN BELT AND ADJACENT AREAS DURING WEEK-2 DUE TO THE AFOREMENTIONED
WARMTH, THE EXPECTATION OF BELOW-NORMAL PRECIPITATION, AND PRECIPITATION TOTALS
ONE TO THREE INCHES BELOW NORMAL FOR THE PAST 30 TO 60 DAYS. SOIL MOISTURE IS
CURRENTLY BELOW THE 30TH CLIMATOLOGICAL PERCENTILE OVER MANY OF THESE AREAS.
DUE TO THESE FACTORS, A RAPID ONSET DROUGHT RISK IS HIGHLIGHTED ACROSS PARTS OF
THE EASTERN CORN BELT, SPECIFICALLY IN MUCH OF SOUTHERN IOWA, NORTHERN
MISSOURI, CENTRAL ILLINOIS AND INDIANA, AND SOUTHERN OHIO.
SNOWMELT CONTINUES ACROSS THE WESTERN CONUS AFTER ACCUMULATING A VERY LARGE AND
IN SOME CASES RECORD-BREAKING SNOWPACK, INDUCING RIVER FLOODING ESPECIALLY
ACROSS HIGHER ELEVATIONS FOR SOME AREAS IN THE WEST, WHERE A FEW SITES STILL
REPORT OVER 40 INCHES OF SNOW WATER CONTENT. AS SNOWMELT CONTINUES IN PARTS OF
THE SIERRA NEVADA, GREAT BASIN, AND NORTHERN ROCKIES, FLOODING MAY CONTINUE TO
OCCUR ALONG SOME RIVERS, AND IN AREAS ADJACENT TO THE HIGHER ELEVATIONS.
FLOODING IS ALSO EXPECTED TO CONTINUE ALONG THE JAMES RIVER IN SOUTH DAKOTA AS
RIVER LEVELS HAVE BEEN VERY SLOW TO RECEDE DUE TO SATURATED GROUND CONDITIONS
AND RELATIVELY FLAT TOPOGRAPHY. A SIMILAR SITUATION HAS DEVELOPED ALONG THE
SOURIS RIVER IN NORTH DAKOTA, WHICH SHOULD CAUSE ONGOING MINOR TO MODERATE
FLOODING TO CONTINUE INTO WEEK-2.
WEAK MID-LEVEL FLOW ACROSS ALASKA FAVORS ONLY A SLIGHT TILT IN PROBABILITIES
FOR ABOVE AND BELOW NORMAL TEMPERATURES 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
INCREASING SNOWMELT ACROSS EASTERN ALASKA IS ANTICIPATED TO CONTINUE THE
POTENTIAL FOR RIVER FLOODING THROUGHOUT THE ALASKAN INTERIOR. 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. ANOTHER FACTOR WHICH
COULD IMPACT CONDITIONS OVER PARTS OF ALASKA IS THE EVOLUTION OF SUPER TYPHOON
MAWAR, CURRENTLY WEST OF GUAM IN THE PACIFIC OCEAN WITH TOP WINDS NEAR 170 MPH.
THE TYPHOON IS EXPECTED TO CONTINUE WESTWARD FOR THE NEXT FEW DAYS BEFORE
TURNING TO THE NORTHEAST A FEW HUNDRED MILES EAST OF TAIWAN. AFTER RECURVATURE,
THE STORM IS ANTICIPATED TO SLOWLY BECOME EXTRATROPICAL WHILE CONTINUING
NORTHEASTWARD, BUT STILL REMAIN A POTENT STORM SYSTEM. SOME TOOLS BRING THE
REMNANTS OF MAWAR CLOSE TO ALASKA DURING WEEK-2, WHICH WOULD SIGNIFICANTLY
IMPACT SOME PART OF THE STATE. DUE TO MODEL GUIDANCE BEING TOO INCONSISTENT,
THERE ARE NO HIGHLIGHTED HAZARD RISKS ASSOCIATED WITH THIS SCENARIO AT THIS
TIME.
FORECASTER: DANNY BARANDIARAN
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