534
FXUS02 KWBC 210455
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1255 AM EDT TUE APR 21 2026
VALID 12Z FRI APR 24 2026 - 12Z TUE APR 28 2026
..OVERVIEW
A FAIRLY ACTIVE AND PROGRESSIVE LARGE-SCALE PATTERN WILL PERSIST
ACROSS MUCH OF CONUS AS A MID/UPPER-LEVEL LOW AND TROUGH WILL
GRADUALLY TRANSLATE EAST ACROSS THE NORTHERN PLAINS INTO THROUGH THE
WEEKEND, WITH TROUGHING EXTENDING BACK INTO THE WEST. THIS SYSTEM
WILL BRING STRONG WINDS ACROSS THE WEST AND PLAINS, WITH SOME
LINGERING RAIN AND MOUNTAIN SNOW THROUGH FRIDAY. AS THE TROUGH AND
STRENGTHENING SURFACE LOW INTERACTS WITH A NORTHERN STREAM OF GULF
MOISTURE, EPISODES OF HEAVY RAIN AND SEVERE WEATHER WILL BECOME
MORE LIKELY ACROSS PARTS OF THE CENTRAL U.S. AND MUCH OF THE
EASTERN U.S. THROUGH THE PERIOD. THE SYSTEM WILL BRING PERIODS OF
ANOMALOUS WARMTH AHEAD OF IT FOR THE EAST AND LATE- SEASON COOL
INTRUSIONS AS BELOW AVERAGE TEMPERATURES EXPAND FROM THE WESTERN
U.S. TO THE CENTRAL U.S. BEHIND A STRONG EASTWARD ADVANCING COLD
FRONT.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST DETERMINISTIC MODEL SUITE REMAINS IN REASONABLY GOOD
AGREEMENT ON THE SYNOPTIC-SCALE EVOLUTION THROUGH DAY 5 (SUNDAY),
PARTICULARLY REGARDING THE PROGRESSION OF THE PACIFIC TROUGH OVER
WESTERN/CENTRAL U.S. INTO SOUTH-CENTRAL CANADA. LATER IN THE
PERIOD, SPREAD INCREASES WITH RESPECT TO THE TIMING AND AMPLITUDE
OF THE SHORTWAVE ENERGY EMBEDDED WITHIN THE MEAN FLOW. DIFFERENCES
ARE ALSO APPARENT IN A PACIFIC ENERGY DEVELOPING TOWARDS DAY 6-7.
THE NBM PROVIDES A GOOD BASELINE FOR THE SENSIBLE WEATHER FIELDS,
WITH INCORPORATING THE ENSEMBLE MEANS TO MITIGATE SOME OF THE
FINER AND SMALL SCALE DIFFERENCES. THEREFORE, THE FORECAST
MAINTAINED A MULTI-MODEL BLEND WEIGHTED TOWARDS DETERMINISTIC
GUIDANCE FOR THE FIRST PORTION OF THE PERIOD, AND THE ENSEMBLE
MEANS TOWARD THE LATER IN THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER LOW OVER THE NORTHERN HIGH PLAINS WILL GRADUALLY LIFT
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 HEAVY PRECIPITATION POSSIBLE ALONG FAVORED
TERRAIN OVER THE INTERMOUNTAIN WEST, ROCKIES, AND PLAINS.
ACCUMULATING SNOW WILL PRIMARY BE CONFINED TO HIGHER ELEVATIONS,
WITH IMPACTS LIMITED TO HIGH MOUNTAIN PASSES AND MOUNTAIN TOWNS. IN
ADDITION, STRONG GUSTY WINDS ARE EXPECTED ACROSS PARTS OF THE
ROCKIES INTO THE PLAINS.
THIS SYSTEM WILL SUPPORT THE 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 INTO OHIO/TENNESSEE VALLEY. THIS FLOODING THREAT IS
HIGHLIGHTED BY A MARGINAL RISK IN THE DAY 4/FRIDAY ERO. GIVEN
INCREASING SOIL MOISTURE FROM PREVIOUS BOUTS OF CONVECTION, AN
UPGRADE TO A SLIGHT RISK IS NOT OUT OF THE QUESTION IN FUTURE
UPDATES.
THE FRONT WILL BEGIN TO 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. OVER INTO THE WEST, THE UPPER-LEVEL TROUGH LINGERING OVER
THE WEST WILL MAINTAIN UNSETTLED CONDITIONS THROUGH MONDAY,
INCLUDING LOWER ELEVATION RAIN AND MOUNTAIN SNOW.
BELOW NORMAL TEMPERATURES OVER MUCH OF WESTERN U.S. WILL EXPAND
EAST INTO THE NORTHERN/CENTRAL PLAINS BY FRIDAY AND PARTS OF THE
MISSISSIPPI VALLEY BY THE WEEKEND BEHIND THE COLD FRONT. PARTS OF
THE NORTHERN PLAINS/ROCKIES WILL DROP TO 20-25 DEGREES BELOW NORMAL,
WHERE HIGHS WILL DROP BETWEEN 30S AND 40S ON FRIDAY THROUGH SUNDAY.
AHEAD OF THE FRONTAL SYSTEM, ABOVE AVERAGE TEMPERATURES WILL PERSIST
THROUGH FRIDAY ACROSS THE SOUTHERN PARTS OF CENTRAL U.S. INTO MUCH
OF THE EASTERN U.S. BEFORE TEMPERATURES MODERATE INTO THE WEEKEND
INTO THE BEGINNING OF THE NEXT WEEK. OVER THE PACIFIC NORTHWEST,
TEMPERATURES WILL BEGIN TO TREND SLIGHTLY ABOVE AVERAGE LATE IN THE
PERIOD AS UPPER LEVEL RIDGING SNEAKS INTO THE REGION.
OUDIT
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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