557
FXUS02 KWBC 131835
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
235 PM EDT TUE MAY 13 2025
VALID 12Z FRI MAY 16 2025 - 12Z TUE MAY 20 2025
...HEAT BUILDS ACROSS THE SOUTHERN PLAINS WHILE LATE SEASON SNOW
IS EXPECTED FOR THE ROCKIES...
..GENERAL OVERVIEW
THE STRONG LOW PRESSURE SYSTEM OVER THE NORTHERN PLAINS ON
THURSDAY IS FORECAST TO LIFT NORTHEAST ACROSS ONTARIO GOING INTO
FRIDAY, WITH A STRONG TRAILING COLD FRONT DRAPING THROUGH THE MID-
SOUTH. NUMEROUS SHOWERS AND STORMS ARE LIKELY ALONG AND AHEAD OF
THE FRONT FROM THE MID- SOUTH TO THE OHIO VALLEY AND GREAT LAKES.
ATTENTION THEN TURNS TO THE INTERMOUNTAIN WEST BY THE WEEKEND AS
ANOTHER AMPLIFIED UPPER TROUGH AND CLOSED LOW DEVELOPS AND BRINGS
ADDITIONAL ROUNDS OF VALLEY RAIN AND MOUNTAIN SNOW ALONG WITH COLD
CONDITIONS FOR THIS TIME OF YEAR. EARLY SEASON HEAT WILL CONTINUE
TO MAKE WEATHER HEADLINES FOR THE SOUTH- CENTRAL U.S. WITH AN UPPER
RIDGE AXIS GOVERNING THE OVERALL WEATHER PATTERN.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 12Z MODEL GUIDANCE SUITE TODAY CONTINUES TO OFFER VERY GOOD
SYNOPTIC SCALE AGREEMENT FOR THE END OF THE WEEK, WITH A MULTI-
DETERMINISTIC MODEL BLEND SUFFICING AS A STARTING POINT IN THE
FORECAST PROCESS AND SLIGHTLY MORE WEIGHTING APPLIED TO THE
ECMWF/GFS SOLUTIONS. THE UKMET REMAINS A BIT NORTH OF THE BETTER
CONSENSUS WITH THE GREAT LAKES LOW AND THEN LATER IN THE PERIOD
THERE ARE SOME DIFFERENCES WITH HOW THIS ENERGY MAY OR MAY NOT
COMBINE WITH ANOTHER SHORTWAVE TO THE NORTH, OR THE EVOLUTION OF
THIS OFF THE NORTHEAST COAST. GUIDANCE AGREES WELL WITH ANOTHER
TROUGH AMPLIFYING OVER THE WEST THIS WEEKEND, WITH AN EVENTUAL
CLOSED LOW LOCATED OVER/NEAR THE CENTRAL GREAT BASIN. THIS LOW WILL
EVENTUALLY LIFT NORTHWARD INTO THE NORTH-CENTRAL U.S. EARLY NEXT
WEEK BUT WITH PLENTY OF UNCERTAINTY IN ENERGY DISPERSION WITHIN AND
AROUND LOW WHICH WOULD HAVE IMPLICATIONS ON SENSIBLE WEATHER
ACROSS THIS REGION. THE WPC FORECAST TRENDED TOWARDS THE ENSEMBLE
MEANS LATE PERIOD WHICH SHOWED BETTER CONSISTENCY AND SMOOTHED OUT
THE SMALLER SCALE DIFFERENCES.
..WEATHER/HAZARDS HIGHLIGHTS
SHOWERS AND THUNDERSTORMS INCREASE IN COVERAGE AND INTENSITY
ACROSS THE MID-SOUTH AND OHIO VALLEY AHEAD OF A COLD FRONT THAT
WILL BE INTERCEPTING DEEPER RETURN MOISTURE. AN BROAD ERO MARGINAL
RISK AREA REMAINS VALID FOR FRIDAY (DAY 4) FROM ARKANSAS TO THE
CENTRAL APPALACHIANS, INCLUDING PORTIONS OF THE OHIO VALLEY. GOING
INTO SATURDAY (DAY 5) ATTENTION THEN TURNS TO PORTIONS OF THE
SOUTHERN PLAINS AND EXTENDING TO THE MID-SOUTH WITH ENHANCED
MOISTURE CONVERGENCE NEAR THE SAME FRONTAL BOUNDARY AND AHEAD OF A
DEVELOPING WAVE OF LOW PRESSURE NEAR THE TEXAS PANHANDLE. ANOMALOUS
MOISTURE COMBINED WITH LOW FLASH FLOOD GUIDANCE VALUES ACROSS
PARTS OF THE NORTHEAST ALLOWED FOR THE INTRODUCTION OF A MARGINAL
RISK AREA ON THE DAY 5/SATURDAY ERO FOR THIS REGION AHEAD OF A
DEPARTING FRONT AND REDEVELOPMENT OF LOW PRESSURE OFFSHORE.
ELSEWHERE ACROSS THE NATION, THE STORM PREDICTION CENTER IS
MONITORING THE POTENTIAL FOR SEVERE WEATHER FROM THE MIDWEST TO THE
MID-SOUTH TO CLOSE OUT THE WORK WEEK WITH FAVORABLE INSTABILITY
AND KINEMATICS. ACROSS THE ROCKIES, EXPECT ADDITIONAL CHANCES FOR
LATE SEASON SNOW FOR THE CENTRAL AND NORTHERN ROCKIES BY SUNDAY
INTO MONDAY AS THE NEXT UPPER TROUGH AND SHORTWAVE MOVES IN, WITH
THE POTENTIAL FOR OVER A FOOT OF ACCUMULATION FOR SOME OF THE
HIGHEST MOUNTAIN RANGES. AT LEAST LOCALLY HEAVY RAINFALL SEEMS
LIKELY TO DEVELOP ACROSS THE GREAT BASIN OVER THE WEEKEND AND INTO
THE NORTH-CENTRAL U.S. EARLY NEXT WEEK IN RESPONSE TO THE
DEVELOPING UPPER LOW WHICH WILL CONTINUE TO BE MONITORED.
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 SOME LOWER-MIDDLE 90S FROM THE OHIO VALLEY AND MID-
ATLANTIC SOUTHWARD TO THE GULF COAST. EARLY SEASON EXCESSIVE HEAT
IS EXPECTED ACROSS SOUTHERN TEXAS THROUGH THE UPCOMING WEEKEND WITH
HIGHS EXCEEDING 100 DEGREES NEAR THE RIO GRANDE AND INTO MUCH OF
CENTRAL TEXAS, AND HEATRISK REACHING THE MAJOR TO EXTREME CATEGORY
FOR SOME OF THESE AREAS, WITH TEMPERATURES IN THE 70S PROVIDING
LITTLE TO NO RELIEF OVERNIGHT. IN CONTRAST, CHILLY CONDITIONS ARE
LIKELY FOR THE INTERMOUNTAIN WEST AND NORTHERN ROCKIES/PLAINS WITH
HIGHS RUNNING 10 TO PERHAPS 20 DEGREES BELOW AVERAGE WITH THE UPPER
LEVEL TROUGH AND INCREASED CLOUD COVER.
SANTORELLI/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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