479
FXUS02 KWBC 211936
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
336 PM EDT TUE APR 21 2026
VALID 12Z FRI APR 24 2026 - 12Z TUE APR 28 2026
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE SOLUTIONS REMAIN REASONABLY WELL CLUSTERED WITH THE MID-
LARGER SCALE PATTERN EVOLUTION OVER MUCH OF THE NEXT WEEK,
BOLSTERING FORECASY CONFIDENCE. A BROAD COMPOSITE BLEND OF THE
LATEST GFS/ECMWF/UKMET/CANADIAN MODELS AND GEFS/ECMWF/CANADIAN
ENSEMBLE MEANS ALONG WITH EC-AIFS MACHINE LEARNING GUIDANCE SEEMS
TO PROVIDE A SOLID FORECAST BASIS GENERALLY IN LINE WITH NATIONAL
BLEND OF MODEL GUIDANCE THROUGH MEDIUM-RANGE TIME SCALES FOR MOST
AREAS. THIS SOLUTION TENDS TO ADDRESS LINGERING SMALLER SCALE
GUIDANCE DIFFERENCES AS CONSISTENT WITH INDIVIDUAL PREDICTABILITY
IN AN EFFORT TO MAINTAIN BEST POSSIBLE PRODUCT CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER LOW OVER THE NORTHERN HIGH PLAINS WILL GRADUALLY LIFT
AND SETTLE INTO SOUTH-CENTRAL CANADA LATE THIS WEEK, CARRYING
MULTIPLE EMBEDDED SHORTWAVES ROTATING AROUND THE BASE OF THE
TROUGH. THIS WILL CONTINUE TO BRING PERIODS OF LOW ELEVATION RAIN
AND MOUNTAIN SNOW, WITH LOCALLY HEAVIER PRECIPITATION POSSIBLE
ALONG FAVORED TERRAIN OVER THE INTERMOUNTAIN WEST, ROCKIES, AND
INTO THE PLAINS. MOST ACCUMULATING SNOW WILL PRIMARILY BE CONFINED
TO HIGHER ELEVATIONS, WITH MAIN IMPACTS LIMITED TO HIGH MOUNTAIN
PASSES AND MOUNTAIN TOWNS, ALBEIT SPILLING INTO THE NORTHERN HIGH
PLAINS. IN ADDITION, STRONG GUSTY WINDS ARE EXPECTED ACROSS PARTS
OF THE ROCKIES INTO THE PLAINS. NBM 5.0 IS SCHEDULED TO BECOME
OPPERATIONAL TOMORROW AND USED THOSE ENHANCED WINDS/GUSTS VALUES.
THIS SYSTEM WILL SUPPORT AN EASTWARD PROJECTION OF A SURFACE LOW
AND COLD FRONT ACROSS THE PLAINS INTO THE MIDWEST BY THE END OF THE
WEEK AND EVENTUALLY THE EAST BY THE WEEKEND. THE COLD FRONT WILL
INTERACT WITH WARM GULF MOISTURE AND AN UNSTABLE AIRMASS, WHICH
WILL SUPPORT A CORRIDOR OF SHOWERS AND THUNDERSTORMS ACROSS THE
PLAINS INTO MUCH OF THE EASTERN U.S. THROUGH THE WEEKEND. THE
COMBINATION OF THE LARGE SCALE FORCING AND INCREASING INSTABILITY
ALONG AND AHEAD OF A STRENGTHENING SURFACE LOW AND STRONG COLD
FRONT, WILL SUPPORT WIDESPREAD CLUSTERS OF STRONG TO SEVERE
THUNDERSTORMS WITH THE POTENTIAL FOR LOCALLY HEAVY RAINFALL AND
ISOLATED FLASH FLOODING OVER THE PARTS OF MID/LOWER MISSISSIPPI
VALLEY TO OHIO/TENNESSEE VALLEY. THIS FLOODING THREAT IS
HIGHLIGHTED BY A MARGINAL RISK AREA IN THE DAY 4/FRIDAY EXCESSIVE
RAINFALL OUTLOOK (ERO). GIVEN INCREASING SOIL MOISTURE FROM REPEAT
BOUTS OF CONVECTION, AN UPGRADE TO A SLIGHT RISK IS NOT OUT OF THE
QUESTION IN FUTURE UPDATES TO MONITOR. THE FRONT WILL THEN DRAPE
ACROSS MUCH OF THE SOUTHERN U.S. AND WILL SLOWLY MOVE ACROSS THE
SOUTHEAST THROUGH THE WEEKEND, WITH A CHANCE FOR A WEAK AREA OF LOW
PRESSURE REDEVELOPING ALONG THE FRONT. THIS WILL REINFORCE SHOWERS
AND THUNDERSTORM THREATS ACROSS THE SOUTH-CENTRAL PLAINS, OHIO
VALLEY, AND SOUTHEAST THROUGH MONDAY, WITH LOCALLY HEAVY RAINFALL
AND POSSIBLE FLOOD THREAT TO MONITOR.
BACK OVER INTO THE WEST, THE UPPER-LEVEL TROUGH LINGERING OFFSHORE
TO OVER THE WEST WILL MAINTAIN UNSETTLED CONDITIONS OVER THE
WEEKEND, INCLUDING LOWER ELEVATION RAIN AND MOUNTAIN SNOW AS POST-
FRONTAL COLD AIR FILTERS DOWN INTO THE WEST. THERE IS A GROWING
SIGNAL THAT A PARTICULARLY ENERGETIC SOUTHERN STREAM UPPER TROUGH
MAY WORK INLAND INTO THE SOUTHWEST SUNDAY WITH ANOTHER ROUND OF
WIDESPREAD RAIN/MOUNTAIN SNOWS ALONG/NORTH OF THE MAIN SYSTEM TRACK
FROM THE GREAT BASIN TO THE ROCKIES, LINGERING THERE INTO MONDAY.
BY MONDAY, EXPECT DOWNSTREAM SYSTEM TRANSLATION WILL LEAD TO PLAINS
CYCLOGENESIS WITH THE ORGANIZED LOW AND ASSOCIATED FRONTAL SYSTEM
TRACK INTO THE GREAT LAKES/MIDWEST TUESDAY SPREADING POTENTIAL FOR
ENHANCED RAINFALL ACROSS THE CENTRAL TO EASTERN U.S. TO MONITOR.
OUDIT/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, 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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