603
FXUS02 KWBC 201914
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 PM EDT WED MAY 20 2026
VALID 12Z SAT MAY 23 2026 - 12Z WED MAY 27 2026
...HEAVY RAIN AND THUNDERSTORMS EXPECTED TO CONTINUE ACROSS
EASTERN TEXAS INTO THE LOWER MISSISSIPPI RIVER VALLEY...
..OVERVIEW
A SLOW-MOVING UPPER LOW WILL TRACK ACROSS THE SOUTH-CENTRAL U.S.
THIS MEMORIAL DAY WEEKEND, WHILE MOISTURE AND INSTABILITY FEED
INTO A WEAK FRONTAL BOUNDARY. THIS WILL PRODUCE WIDESPREAD SHOWERS
AND THUNDERSTORMS FOR THAT REGION, AND FLOODING WILL BE A CONCERN
AS RAIN TOTALS PILE UP. MEANWHILE A NORTHERN STREAM UPPER TROUGH IS
FORECAST TO PUSH ACROSS THE NORTH-CENTRAL U.S., BRINGING RAIN TO
THE NORTHEASTERN QUADRANT OF THE U.S. FOR THE WEEKEND AND
POTENTIALLY LASTING INTO MONDAY. A DEEPER UPPER TROUGH/LOW IS
FORECAST TO ARRIVE IN THE NORTHWEST EARLY NEXT WEEK, YIELDING
COOLER TEMPERATURES AND PRECIPITATION, AS WELL AS DEVELOPING A MORE
AMPLIFIED PATTERN AS A DOWNSTREAM UPPER RIDGE DEVELOPS ACROSS THE
EAST-CENTRAL U.S. BY MIDWEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE SHOWS REASONABLE AGREEMENT THROUGH THE WEEKEND WITH
THE PRIMARY FEATURES OF NOTE, INCLUDING THE NORTH-CENTRAL AND
SOUTH-CENTRAL UPPER TROUGHS MENTIONED ABOVE. TYPICAL SMALLER SCALE
DIFFERENCES COULD CAUSE SENSIBLE WEATHER DIFFERENCES LIKE PLACEMENT
OF QPF, BUT THESE WILL LIKELY REMAIN UNCERTAIN INTO THE SHORT
RANGE. THE NORTHERN STREAM TROUGH WILL SHIFT ACROSS SOUTHEASTERN
CANADA MONDAY-TUESDAY WHILE THE SOUTHERN STREAM TROUGH ERODES
DURING THAT TIME. A MULTI-MODEL BLEND WORKED WELL FOR THE EARLY
PART OF THE PERIOD.
THE PRIMARY LARGER SCALE MODEL VARIATIONS ARE WITH THE UPPER
TROUGH MOVING TOWARD AND INTO THE NORTHWEST EARLY TO MID-NEXT WEEK.
THE 00/06Z MODEL GUIDANCE SUITE WAS RATHER AGREEABLE WITH ITS
TRACK AND TIMING OF THE TROUGH AND EMBEDDED LOW. HOWEVER, THE NEWER
12Z SUITE HAS DIVERGED SOMEWHAT, WITH THE GFS A BIT FARTHER EAST
AND THE CMC FARTHER SOUTHWEST BY TUESDAY-WEDNESDAY. THE 12Z ECMWF
SEEMS TO BE LOCATED THE CLOSEST TO PREVIOUS CONSENSUS, SO WOULD
FAVOR THAT POSITION, WHICH IS A GOOD MIDDLE GROUND AND IN LINE WITH
THE ENSEMBLE MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
HEAVY RAIN WILL CONTINUE TO MAKE WEATHER HEADLINES GOING INTO THE
MEMORIAL DAY WEEKEND ACROSS MUCH OF THE SOUTH-CENTRAL U.S. AS
MULTIPLE MESOSCALE CONVECTIVE SYSTEMS DEVELOP. THESE WILL BE IN
RESPONSE TO ENHANCED ASCENT FROM A SOUTHERN STREAM UPPER TROUGH
COUPLED WITH A WEAK FRONT IN THE REGION AND PLENTY OF MOISTURE AND
INSTABILITY. SLIGHT RISKS FOR EXCESSIVE RAINFALL REMAIN IN PLACE
FOR SOUTHERN/SOUTHEASTERN TEXAS AND WESTERN LOUISIANA ON DAY
4/SATURDAY AND SHIFTED A BIT EAST ON DAY 5/SUNDAY, WHERE THE
POTENTIAL EXISTS FOR SEVERAL INCHES OF RAINFALL OVER THIS TIME
PERIOD OVER SOILS THAT WILL BE BECOMING INCREASINGLY SATURATED.
ANOTHER CORRIDOR OF MODERATE TO HEAVY RAINFALL IS POSSIBLE ACROSS
NORTHERN PORTIONS OF THE MID-ATLANTIC AND SOUTHERN PORTIONS OF THE
NORTHEAST ON SATURDAY, WHERE INSTABILITY WILL BE LIMITED BUT
MOISTURE ANOMALIES WILL BE HIGH AND A FRONTAL SYSTEM IS IN PLACE TO
FOCUS THE MOISTURE. A MARGINAL RISK REMAINS IN PLACE FOR THE DAY 4
ERO IN THAT CORRIDOR, BUT ITS POSITION COULD CONTINUE TO SHIFT
AROUND AS MODEL SPREAD PERSISTS. FARTHER SOUTH, SCATTERED SHOWERS
AND THUNDERSTORMS ARE LIKELY TO DEVELOP ACROSS THE SOUTHEAST AND
CAROLINAS THIS WEEKEND INTO NEXT WEEK. DESPITE DROUGHT CONDITIONS,
THERE MAY BE A NONZERO CHANCE OF FLASH FLOODING IN THESE AREAS
WHERE RAIN RATES ARE HIGH, BUT WILL KEEP THIS SUB-MARGINAL RISK
FOR NOW.
UPPER TROUGHING MOVING INTO THE NORTHWEST EARLY NEXT WEEK AND A
FRONTAL SYSTEM AHEAD OF IT WILL ALLOW FOR INCREASED PRECIPITATION
REACHING THE PACIFIC NORTHWEST SUNDAY AND SPREADING SOUTHEAST ON
MONDAY AND TUESDAY. SNOW IS POSSIBLE AT THE HIGHEST ELEVATIONS OF
THE CASCADES TO ROCKIES. THE FOUR CORNERS STATES CAN ALSO EXPECT
INCREASING RAIN AND THUNDERSTORM CHANCES BY MONDAY.
LINGERING CLOUD COVER AND RAINFALL WITH RESIDUAL COLD AIR DAMMING
ACROSS PORTIONS OF THE MID-ATLANTIC AND NORTHEAST SHOULD CONTINUE
TO KEEP TEMPERATURES ON THE COOL SIDE ON SATURDAY, WITH HIGHS
RUNNING 10-20 DEGREE BELOW AVERAGE BEFORE A GRADUAL MODERATING
TREND ENSUES BY EARLY NEXT WEEK. IT SHOULD ALSO BE SLIGHTLY BELOW
AVERAGE ACROSS TEXAS GIVEN THE WIDESPREAD RAINFALL THAT IS EXPECTED
THROUGH THE WEEKEND. WITH THE UPPER LOW DEVELOPING OVER THE
NORTHWESTERN U.S., A RETURN TO COLDER CONDITIONS IS ALSO LIKELY
IN THAT REGION GOING INTO TUESDAY AND WEDNESDAY. THE GREATEST
POSITIVE TEMPERATURE ANOMALIES WILL LIKELY BE OVER THE NORTHERN
PLAINS AND UPPER MIDWEST WITH THE UPPER RIDGE AXIS MONDAY THROUGH
WEDNESDAY, WITH READINGS UP TO 20 DEGREES ABOVE AVERAGE.
TATE/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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