536
FXUS02 KWBC 110658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT SUN MAY 11 2025
VALID 12Z WED MAY 14 2025 - 12Z SUN MAY 18 2025
..HEAVY RAIN FOR THE NORTHERN PLAINS AND HEAT BUILDS ACROSS TEXAS
..GENERAL OVERVIEW
THE SLOW MOVING UPPER LOW ACROSS THE SOUTHEAST U.S. WILL BE
WEAKENING AND EVOLVING INTO AN OPEN TROUGH BY THURSDAY AS IT EXITS
THE EAST COAST. ANOTHER UPPER TROUGH AND CLOSED LOW ACROSS THE
NORTHERN ROCKIES MID-WEEK WILL SUSTAIN A SURFACE LOW CROSSING THE
NORTHERN PLAINS AND THEN INTO SOUTH-CENTRAL CANADA BY THE END OF
THE WEEK, WITH HEAVY RAIN FOR THE DAKOTAS/MINNESOTA AND LATE
SEASON MOUNTAIN SNOW FOR THE NORTHERN ROCKIES. A SECOND TROUGH WILL
LIKELY DEVELOP ACROSS THE INTERIOR WEST BY NEXT WEEKEND WITH AN
UPPER RIDGE TRYING TO RE-DEVELOP ACROSS THE PLAINS. WIDESPREAD
ABOVE NORMAL TEMPERATURES ARE LIKELY EAST OF THE ROCKIES THROUGH
MUCH OF THE FORECAST PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE FEATURES VERY GOOD SYNOPTIC SCALE
AGREEMENT FOR THE MIDDLE OF THE WEEK, WITH A MULTI-DETERMINISTIC
MODEL BLEND SUFFICING AS A STARTING POINT IN THE FORECAST PROCESS.
THE ECMWF IS SLIGHTLY SOUTH OF THE MODEL CONSENSUS BY FRIDAY WITH
THE LOCATION OF THE CLOSED LOW OVER MINNESOTA, BUT STILL HAS ENOUGH
ENSEMBLE AND MACHINE LEARNING GUIDANCE SUPPORT TO INCLUDE IN THE
MODEL PREFERENCES. LOOKING AHEAD TO NEXT SATURDAY, THE GUIDANCE
BEGINS TO DIFFER MORE SUBSTANTIALLY ACROSS THE WESTERN U.S. AS A
SECOND UPPER TROUGH LIKELY DEVELOPS. GIVEN THE NORTHWARD
DISPLACEMENT WITH THE LOW ACROSS SOUTHERN CANADA WITH THE 12Z CMC,
THE WPC FRONT/PRESSURES RELIED MORE ON THE GFS/ECMWF/ENSEMBLE
MEANS BY NEXT WEEKEND, WITH ABOUT HALF MEANS BY SUNDAY.
..WEATHER/HAZARDS HIGHLIGHTS
THE REGION WITH HEAVIEST RAINFALL GOING INTO THE SECOND HALF OF THE
WORK WEEK WILL BE ACROSS THE NORTHERN PLAINS ON THE BACK SIDE OF
THE DEVELOPING SURFACE LOW. ALTHOUGH RAINFALL RATES ARE NOT
EXPECTED TO BE ALL THAT HIGH, MULTIPLE HOURS OF MODERATE RAINFALL
WITH RATES OF HALF AN INCH PER HOUR IN SOME CASES MAY JUST BE
ENOUGH TO CAUSE SOME MINOR FLOODING ISSUES IN VULNERABLE AREAS, AND
THEREFORE THE MARGINAL RISK AREA HAS BEEN MAINTAINED FOR WEDNESDAY
(DAY 4) FROM EASTERN MONTANA INTO WESTERN NORTH DAKOTA. GOING INTO
THURSDAY (DAY 5), THE HEAVIER RAINFALL REACHES EASTERN NORTH DAKOTA
INTO NORTHERN MINNESOTA WHERE A MARGINAL RISK AREA IS NOW PLANNED,
WITH SOME OF THE GUIDANCE INDICATING THE POTENTIAL FOR 1-2 INCH
RAINFALL TOTALS WITH SOME EMBEDDED CONVECTION.
ELSEWHERE ACROSS THE NATION, QPF HAS TRENDED A LITTLE LOWER ACROSS
THE MID-ATLANTIC REGION FOR WEDNESDAY AS THE FORCING ASSOCIATED
WITH THE UPPER LOW WEAKENS AND CONVECTION IS MORE SCATTERED AND
LESS ORGANIZED. AFTER CONSULTATION WITH AFFECTED WFOS, THE MARGINAL
RISK HAS BEEN DROPPED FOR THE NEW DAY 4 PERIOD. THE STORM
PREDICTION CENTER IS ALSO MONITORING THE POTENTIAL FOR SOME SEVERE
STORMS ON THURSDAY ACROSS PORTIONS OF THE MIDWEST. OUT WEST, OLD
MAN WINTER WILL CONTINUE TO MAKE ITS PRESENCE KNOWN ACROSS THE
NORTHERN ROCKIES WITH HEAVY SNOW FOR THE HIGHEST RANGES OF
SOUTHWESTERN MONTANA AND NORTHERN WYOMING, WITH THE POTENTIAL FOR
6-12 INCHES OF ACCUMULATION IN SOME CASES. LIGHTER SNOWS ARE LIKELY
ELSEWHERE ACROSS THE HIGHER TERRAIN OF THE NORTHERN ROCKIES AND
INTERMOUNTAIN WEST.
VERY WARM WEATHER WILL CONTINUE ACROSS THE UPPER MIDWEST FOR THE
MIDDLE OF THE WEEK, WITH HIGHS REACHING 85-90 DEGREES ON WEDNESDAY
ACROSS THE EASTERN DAKOTAS AND MUCH OF MINNESOTA. THE ANOMALOUS
WARMTH THEN SHIFTS EASTWARD TO THE GREAT LAKES AND OHIO VALLEY
REGIONS TO CLOSE OUT THE WEEK, AND MUCH OF THE EAST COAST FRIDAY
INTO SATURDAY AHEAD OF THE COLD FRONT. VERY HOT CONDITIONS ARE
EXPECTED ACROSS SOUTHERN TEXAS FOR THE ENTIRE FORECAST PERIOD WITH
HIGHS EXCEEDING 100 DEGREES NEAR THE RIO GRANDE, AND HEATRISK
REACHING THE MAJOR CATEGORY FOR THESE AREAS. IN CONTRAST, CHILLY
CONDITIONS ARE LIKELY FOR THE INTERMOUNTAIN WEST AND NORTHERN
ROCKIES WITH HIGHS RUNNING 5-15 DEGREES BELOW AVERAGE WITH THE
UPPER LEVEL TROUGH AND INCREASED CLOUD COVER.
HAMRICK
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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