559
FXUS02 KWBC 181735
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 PM EDT MON MAY 18 2026
VALID 12Z THU MAY 21 2026 - 12Z MON MAY 25 2026
***MULTIPLE ROUNDS OF HEAVY RAIN AND SEVERE STORMS EXPECTED FOR THE
SOUTHERN PLAINS, AND EARLY SEASON HEATWAVE ENDS FOR THE EAST
COAST STATES***
..GENERAL OVERVIEW
A MODERATELY AMPLIFIED UPPER LEVEL PATTERN OVER THE COUNTRY DURING
THE MIDDLE OF THE WEEK IS EXPECTED TO BECOME MORE QUASI-ZONAL BY
NEXT WEEKEND, AS THE TROUGH LIFTS OUT FROM THE ROCKIES AND THE
NORTHERN PLAINS, AND THE EASTERN U.S. RIDGE GETS FLATTENED WITH A
RETURN TO MORE TYPICAL TEMPERATURES FOR THE MONTH OF MAY, WITH
RELIEF FROM THE EARLY SEASON HEAT WAVE. A STALLING FRONTAL BOUNDARY
WITH SHORTWAVE IMPULSES ALOFT WILL FUEL THE DEVELOPMENT OF MULTIPLE
THUNDERSTORM COMPLEXES FROM TEXAS TO THE DEEP SOUTH, WITH EPISODES
OF HEAVY RAINFALL AND STRONG/SEVERE STORMS. MAINLY DRY CONDITIONS
ARE EXPECTED FOR MOST OF THE WESTERN U.S.
..GUIDANCE/PREDICTABILITY ASSESSMENT
OVERALL MODEL AGREEMENT CONTINUES FOR THE LARGE SCALE FEATURES OF
THE QUASI-STATIONARY FLOW THROUGH MUCH OF CONUS AND A TROUGH OVER
WESTERN U.S. THROUGH THE FIRST PORTION OF THE PERIOD. MODELS BEGIN
TO DIVERGE TOWARDS THE WEEKEND IN REGARD TO THE SHORTWAVE FEATURES
ALONG THE SOUTH-SOUTHWEST, ESPECIALLY WITH CMC WHERE THE TROUGH
OVER THE SOUTHWEST IS SLOWER COMPARED TO THE GFS AND ECMWF. IN
ADDITION, THE GFS BEGIN TO SHOW AMPLITUDE DIFFERENCES TOWARDS
SUNDAY. THE ENSEMBLE MEANS SEEM TO SMOOTH SOME OF THESE
DIFFERENCES, BUT THE GEFS CONTINUES AS AN OUTLIER IN REGARD TO
FEATURES OVER THE WEST EARLY NEXT WEEK. ECMWF SHOWS A TROUGH
ENTERING THE WEST COAST BY MONDAY, WHILE THE GFS AND CMC SHOWS
SLOWER SOLUTIONS IN TERMS OF TIMING. THEREFORE, THE WPC FORECAST
ENCOMPASSED A BLEND OF THE CMC/GFS/ECMWF/UKMET/EC- AIFS FOR THE
FIRST PORTION OF THE PERIOD, WHILE INCORPORATING THE ENSEMBLE
MEANS FOR THE REMAINDER OF THE TIMEFRAME.
..WEATHER/HAZARDS HIGHLIGHTS
HEAVY RAINFALL IS EXPECTED TO MAKE WEATHER HEADLINES GOING INTO THE
LATTER HALF OF THE WORK WEEK FROM CENTRAL TEXAS TO THE TENNESSEE
RIVER VALLEY. THE HIGHEST QPF SHOULD BE ACROSS EAST-CENTRAL TEXAS
WHERE MULTIPLE MESOSCALE CONVECTIVE SYSTEMS WILL DEVELOP AND AFFECT
THE SAME AREAS ON MULTIPLE DAYS. FOR THE DAY 4/THURSDAY ERO, A
SLIGHT RISK WILL REMAIN VALID FROM NEAR SAN ANTONIO TO NORTHEAST
TEXAS WHERE 1-3 INCHES OF RAINFALL IS LIKELY WITH STORMS PRODUCING
HIGH RAINFALL RATES. THIS LINGERS GOING INTO FRIDAY AS WELL WITH A
BROAD MARGINAL RISK FOR THE DAY 5/FRIDAY ERO, EXTENDING FROM THE
RIO GRANDE TO OHIO, WITH POSSIBLE UPGRADES TO SLIGHT RISK IN FUTURE
OUTLOOKS AS TIMING AND PLACEMENT BECOME CLEARER.
ELSEWHERE ACROSS THE COUNTRY, LIGHTER PRECIPITATION IS EXPECTED
FARTHER TO THE EAST ACROSS THE CAROLINAS INTO VIRGINIA WITH
OVERRUNNING FLOW NORTH OF THE FRONTAL BOUNDARY. THERE SHOULD ALSO
BE CORRIDORS OF MODERATE RAINFALL ACROSS PORTIONS OF THE
CENTRAL/NORTHERN PLAINS TO THE MIDWEST STATES THROUGH FRIDAY. THE
POTENTIAL EXISTS FOR THIS REGION TO SEE AN UPWARD TREND IN RAINFALL
TOTALS IN FUTURE FORECASTS. MOUNTAIN SNOW ACROSS THE NORTHERN
ROCKIES ON THURSDAY SHOULD ABATE IN INTENSITY BEFORE A DRIER
WEATHER PATTERN ENSUES BY FRIDAY.
IN TERMS OF TEMPERATURES, A WELCOMED RELIEF FROM THE HEAT WAVE
ACROSS THE EASTERN U.S. IS EXPECTED TO ARRIVE ON THURSDAY AS A
STRONG COLD FRONT REACHES THE MID-ATLANTIC, AND THEN DROPS SOUTH
ACROSS NORTH CAROLINA GOING INTO FRIDAY BEFORE STALLING. A COLD
AIR DAMMING TYPE EVENT WILL LIKELY BECOME ESTABLISHED EAST OF THE
APPALACHIANS WITH OVERCAST SKIES AND PERIODS OF MAINLY LIGHT RAIN
AT TIMES, AND WARM AND HUMID CONDITIONS CONTINUING SOUTH OF THE
BOUNDARY. ELSEWHERE, RELATIVELY COOL CONDITIONS ACROSS THE
CENTRAL/NORTHERN PLAINS ARE EXPECTED TO GRADUALLY WARM THROUGH THE
FORECAST PERIOD.
OUDIT/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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