172
FXUS02 KWBC 162019
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
419 PM EDT SAT MAY 16 2026
VALID 12Z TUE MAY 19 2026 - 12Z SAT MAY 23 2026
***MULTIPLE ROUNDS OF HEAVY RAIN AND SEVERE STORMS EXPECTED FOR THE
SOUTHERN PLAINS, AND EARLY SEASON HEATWAVE FOR THE EAST COAST***
..GENERAL OVERVIEW
AN AMPLIFIED UPPER LEVEL PATTERN WILL BE IN PLACE FOR THE
BEGINNING OF NEXT WEEK, WITH AN ANOMALOUS RIDGE OVER THE EAST-
CENTRAL U.S. SUPPORTING AN EARLY SEASON HEAT WAVE, AND A STRONG
TROUGH OVER THE ROCKIES THAT WILL BRING A ROUND OF LATE SEASON SNOW
FOR THE HIGHER ELEVATIONS OF COLORADO AND WYOMING. AT THE
INTERFACE OF THESE TWO FEATURES WILL BE BROAD DIFFLUENT FLOW OVER A
STRONG COLD FRONT THAT WILL CROSS THE PLAINS AND MIDWEST, BRINGING
MULTIPLE ROUNDS OF HEAVY RAINFALL AND STRONG/SEVERE THUNDERSTORMS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MOST OF THE LATEST DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS
WELL-CLUSTERED THROUGH A MAJORITY OF THE PERIOD, WITH THE OVERALL
PATTERN FEATURING A SHIFTING TREND FROM MORE AMPLIFIED FLOW TO
QUASI-ZONAL. AN INITIAL UPPER-LEVEL SHORTWAVE WITHIN MEAN CENTRAL
TO WESTERN U.S. TROUGHING AND ACCOMPANYING LOW PRESSURE/FRONTAL
SYSTEM REFLECTION AT THE SURFACE OVER THE GREAT LAKES SHOWS TYPICAL
SMALLER-SCALE DIFFERENCES IN PROGRESSION AND TRACK AT THIS TIME
FRAME BUT FOLLOWS A MOSTLY AGREEABLE TRAJECTORY NORTHEASTWARD INTO
CANADA. A TRAILING COLD FRONT WILL SPREAD TOWARDS THE EAST AND GULF
COASTS WITH SUBTLE DIFFERENCES IN FRONTAL POSITION AND A POTENTIAL
SOUTHERN STREAM SHORT-WAVE BRINGING UNCERTAINTY TO QPF
COVERAGE/AMOUNTS PARTICULARLY OVER THE SOUTH-CENTRAL U.S., BUT
AGAIN WITH AN AGREEABLE OVERALL PATTERN. THE PROGRESSION OF THE
UPPER-WAVE/SURFACE LOW PRESSURE NOTABLY SLOWED IN THE CMC COMPARED
TO THE OTHER GUIDANCE BY THE MIDDLE PART OF THE PERIOD, WITH THE
LOW STALLING AND WEAKENING IN THE VICINITY OF THE NORTHEAST
COMPARED TO LIFTING NORTHEASTWARD INTO CANADA.
AS THE FLOW TRENDS MORE QUASI-ZONAL, UNCERTAINTY INCREASES WITH
INDIVIDUAL NORTHERN STREAM SHORT-WAVE TIMING/PROGRESSION ACROSS
SOUTHERN CANADA AND INTO THE NORTHWESTERN TO NORTH-CENTRAL U.S.
WITH GROWING DIVERGENCE OVERALL BETWEEN THE DETERMINISTIC GUIDANCE
WITH REGARDS TO AT LEAST ONE IF NOT MORE POSSIBLE SYSTEMS. THE
UPDATED WPC FORECAST WAS BASED ON A COMPOSITE BLEND OF THE 06Z
GFS/EC AIFS AND 00Z ECMWF/CMC/UKMET FOR THE FIRST PART OF THE
PERIOD GIVEN GOOD AGREEMENT, WITH THE CMC DROPPED BY MID-PERIOD
GIVEN THE OUTLIER NATURE OF THE NORTHEASTERN UPPER-WAVE/SURFACE LOW
PROGRESSION. A CONTRIBUTION FROM THE ECENS AND THEN GEFS MEANS
REPLACED THE CMC AND THEN TIME-LIMITED UKMET WHICH ALSO HELPED TO
TREND TOWARDS A COMPROMISE SOLUTION OVER THE NORTHWEST TO NORTH-
CENTRAL U.S. GIVEN GROWING UNCERTAINTY AND ALLOWED FOR GOOD WPC
FORECAST CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
A DYNAMIC STORM SYSTEM CROSSING THE PLAINS WILL BRING WIDESPREAD
SHOWERS AND THUNDERSTORMS FROM TEXAS TO THE OHIO VALLEY AHEAD OF A
STRONG COLD FRONT. ON TUESDAY, THE BEST FOCUS FOR HEAVY RAINFALL IS
EXPECTED TO BE ACROSS TEXAS AND EXTENDING EASTWARD TO ARKANSAS AND
THE MID-SOUTH AS THE FRONT INTERCEPTS DEEPER MOISTURE AND SLOWS
DOWN IN ITS FORWARD PROGRESS. A SLIGHT RISK OF EXCESSIVE RAINFALL
REMAINS OUTLOOKED ACROSS PORTIONS OF SOUTH-CENTRAL TO EASTERN
OKLAHOMA/THE RED RIVER VALLEY AND INTO NORTHWESTERN ARKANSAS.
SPREAD AMONGST THE GUIDANCE WITH REGARDS TO THE FRONTAL POSITION AS
WELL AS POTENTIAL INFLUENCE OF A SUBTLE SOUTHERN STREAM WAVE HAS
RESULTED IN GREATER UNCERTAINTY WITH REGARDS TO THE HIGHEST QPF
LOCATION/COVERAGE ACROSS THE SOUTHERN PLAINS INTO THE OZARKS AND
SOUTHWARD TOWARDS THE GULF COAST. THEREFORE, SOME ADJUSTMENT OF
THIS RISK AREA MAY BE NECESSARY IN THE COMING DAYS, THOUGH
PLENTIFUL MOISTURE/THUNDERSTORM POTENTIAL DOES AT LEAST SUPPORT THE
POTENTIAL FOR SCATTERED FLASH FLOODING. ADDITIONAL HEAVY RAINFALL
IS LIKELY GOING INTO DAY 5/WEDNESDAY WITH A BROAD MARGINAL RISK
EXTENDING FROM WESTERN TEXAS TO THE CENTRAL APPALACHIANS.
IN THE TEMPERATURE DEPARTMENT, HEAT WILL BE MAKING HEADLINES FOR
MUCH OF THE EASTERN U.S. THROUGH THE MIDDLE OF THE WEEK, WITH THE
HOTTEST CONDITIONS ACROSS INTERIOR PORTIONS OF THE MID-ATLANTIC
INTO THE CAROLINAS WHERE HIGHS ARE LIKELY TO REACH THE LOWER TO
MIDDLE 90S. THIS WILL LIKELY BE WARM ENOUGH TO ESTABLISH SOME DAILY
RECORD HIGHS BEFORE A COLD FRONT BRINGS RELIEF FROM THE OHIO
VALLEY TO THE MID-ATLANTIC/NORTHEAST BY THURSDAY WITH MUCH COOLER
TEMPERATURES FORECAST HEADING INTO MEMORIAL DAY WEEKEND. THE
OPPOSITE WILL HOLD TRUE FOR THE INTERMOUNTAIN WEST AND ROCKIES WITH
BELOW NORMAL READINGS TO START THE WEEK, AND SNOW FOR THE HIGHER
ELEVATIONS, FOLLOWED BY A MODERATION TREND.
PUTNAM/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, EXCESSIVE RAINFALL OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY MESSAGES ARE AT:
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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