042
FXUS02 KWBC 121859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT MON MAY 12 2025
VALID 12Z THU MAY 15 2025 - 12Z MON MAY 19 2025
..MAJOR HEAT TO BUILD OVER TEXAS LATE WEEK/WEEKEND
..HEAVY RAIN FOR THE NORTHERN PLAINS INTO LATE WEEK
..GENERAL OVERVIEW
A DEEPLY WET AND SLOW MOVING UPPER LOW NOW WORKING INTO THE
SOUTHEAST U.S. WILL EJECT AND WEAKEN INTO AN OPEN TROUGH INTO
THURSDAY AS IT FINALLY EXITS THE EAST COAST. MEANWHILE, AN UPPER
TROUGH AND CLOSED LOW LIFTING OVER THE NORTHERN ROCKIES WILL
SUPPORT DEEP CYCLOGENESIS UP THROUGH THE NORTHERN PLAINS/UPPER
MIDWEST AND INTO CANADA. THIS WILL SUPPORT WRAPPING HEAVY RAIN FOR
THE DAKOTAS/MINNESOTA AND LINGERING SPRING MOUNTAIN SNOW FOR THE
NORTHERN ROCKIES. LATER, AN UPSTREAM TROUGH WILL DIG INTO THE WEST
COAST BY THE WEEKEND AND GUIDANCE IS TRENDING TO INCREASINGLY
AMPLIFIED DEVELOPING ACROSS THE WEST NEXT WEEKEND AS A WARMING AND
DOWNSTREAM UPPER RIDGE BUILDS OVER MUCH OF THE PLAINS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES OFFER A REASONABLY SIMILAR MID-LARGER SCALE
PATTERN EVOLUTION, ALBEIT WITH SMALLER SCALE VARIANCES STARTING
UNCHARACTERISTICALLY EARLY IN THE FORECAST PERIOD. EVEN SO, A
MODEL COMPOSITE STILL SEEMS TO OFFER A SOLID FORECAST BASE FOR
LATER THIS WEEK WITH ADDITION OF A FEW MANUAL ADJUSTMENTS TO ENSURE
LOW DEPTHS GIVEN UPPER SUPPORT. LATER, BLENDED GEFS/ECMWF/CANADIAN
ENSEMBLE MEANS GUIDANCE COUPLED WITH WPC CONTINUITY. THIS PLAN
TENDS TO MITIGATE DIFFERENCES AS CONSISTENT WITH INDIVIDUAL
PREDICTABILITY. WPC PRODUCT CONTINUITY IS GOOD AND IN LINE WITH
LATEST 12 UTC GUIDANCE TRENDS THAT CONTINUE TO LEAN TOWARD
AMPLIFIED UPPER TROUGH SCENARIOS OVER THE WEST BY THE WEEKEND.
..WEATHER/HAZARDS HIGHLIGHTS
THE REGION WITH HEAVIEST RAINFALL GOING INTO THE SECOND HALF OF THE
WORK WEEK WILL BE IN NORTH DAKOTA AND MINNESOTA. ALTHOUGH RAINFALL
RATES ARE NOT EXPECTED TO BE VERY HIGH, MULTIPLE HOURS OF MODERATE
RAINFALL WITH RATES OF HALF AN INCH PER HOUR IN SOME CASES MAY BE
ENOUGH TO CAUSE MINOR FLOODING ISSUES IN VULNERABLE AREAS, AND
THEREFORE A WPC EXCESSIVE RAINFALL OUTLOOK (ERO) MARGINAL RISK
AREA WAS MAINTAINED FOR DAY 4/THURSDAY FROM EASTERN NORTH DAKOTA
INTO CENTRAL/NORTHERN MINNESOTA. INTO DAY 5/FRIDAY, SHOWERS AND
THUNDERSTORMS INCREASE IN COVERAGE AND INTENSITY ACROSS THE MID-
SOUTH IN THE GENERAL VICINITY OF A QUASI-STATIONARY FRONT THAT
WILL BE INTERCEPTING DEEPER RETURN MOISTURE. AN ERO MARGINAL RISK
AREA WAS MODIFIED SMALLER GIVEN A MORE FOCUS SIGNAL FROM ARKANSAS
TO EASTERN KENTUCKY WHERE THE MODEL QPF/CONVECTION IS STRONGEST.
ELSEWHERE ACROSS THE NATION, THE STORM PREDICTION CENTER OFFERS
POTENTIAL FOR SEVERE STORMS THURSDAY INTO FRIDAY FOR PORTIONS OF
THE MIDWEST/MID-SOUTH. UPSTREAM, EXPECT LINGERING HEAVY SNOW FOR
THE HIGHEST RANGES OF THE NORTHERN ROCKIES INTO THURSDAY,
ADDITIONAL CHANCES FOR SNOW FOR THE CENTRAL AND NORTHERN ROCKIES
BY SUNDAY/MONDAY AS THE NEXT UPPER TROUGH AND SHORTWAVE MOVES IN.
VERY WARM WEATHER WILL BE COMMONPLACE ACROSS THE EASTERN HALF OF
THE COUNTRY TO CLOSE OUT THE WORK WEEK, WITH HIGHS WELL INTO THE
80S AND EVEN LOWER 90S FROM THE OHIO VALLEY AND MID-ATLANTIC
SOUTHWARD TO THE GULF COAST. 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 TO EXTREME CATEGORY FOR SOME OF THESE AREAS. IN
CONTRAST, CHILLY CONDITIONS ARE LIKELY FOR THE INTERMOUNTAIN WEST
AND NORTHERN ROCKIES/PLAINS WITH HIGHS RUNNING 5-15 DEGREES BELOW
AVERAGE WITH THE UPPER LEVEL TROUGH AND INCREASED CLOUD COVER.
HAMRICK/SCHICHTEL
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page