421
FXUS02 KWBC 191924
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
324 PM EDT SUN APR 19 2026
VALID 12Z WED APR 22 2026 - 12Z SUN APR 26 2026
..OVERVIEW
UNSETTLED WEATHER WILL PERSIST THROUGH THE PERIOD AS A PACIFIC
MID/UPPER-LEVEL TROUGH PUSHES ACROSS THE GREAT BASIN, INTERMOUNTAIN
WEST AND NORTHERN ROCKIES BEFORE EJECTING EASTWARD INTO THE
NORTHERN PLAINS MID TO LATE WEEK. THIS SYSTEM WILL BRING VERY
STRONG WINDS AND WIDESPREAD PRECIPITATION, INCLUDING LOW ELEVATION
RAIN AND HEAVY MOUNTAIN SNOW. AS THE TROUGH AND ITS ASSOCIATED
SURFACE LOW INTERACTS WITH SURGING GULF MOISTURE OVER THE CENTRAL
U.S., EPISODES OF HEAVY RAIN AND SEVERE WEATHER WILL BECOME MORE
LIKELY THURSDAY AND FRIDAY. COOLER THAN NORMAL TEMPERATURES WILL
EXPAND FROM THE WESTERN U.S. TO THE CENTRAL U.S. BEHIND A STRONG
EASTWARD ADVANCING COLD FRONT.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL GUIDANCE CONTINUES TO HAVE A FAIRLY DECENT GRASP
OF THE LARGE SCALE PATTERN THROUGH THE MEDIUM RANGE PERIOD. THAT
BEING SAID, UNCERTAINTY REMAINS RELATIVELY HIGH WITHIN THE SMALLER
SCALE DETAILS OF A DYNAMIC MID/UPPER-LEVEL PACIFIC LOW/TROUGH,
ESPECIALLY FOR DAY 5 AND BEYOND. GIVEN THE UNCERTAINTY, THE WPC
FORECAST LEANED MORE HEAVILY INTO THE ECMWF AND GEFS ENSEMBLE MEANS
TO SMOOTH OUT THE SMALL SCALE DIFFERENCES, WITH WEIGHTING OF THE
MEANS INCREASING TO 40% BY DAY 5 AND 60% BY DAY 7. ADDITIONALLY,
THE WEIGHTING OF DETERMINISTIC MODELS LEANED MORE ON THE 00Z EC AND
THE 06Z GFS, WITH LESS WEIGHTING ON THE 00Z CMC AND 00Z EC-AIFS
GIVEN MORE EMPHASIS ON THE DEVELOPMENT OF THE LEAD WAVE VS THE
KICKER WAVE. DESPITE THESE PREFERENCES, SOLUTIONS INVOLVING
MULTIPLE SHORTWAVES ROTATING WITHIN AND AROUND THE PARENT LOW ARE
NOTORIOUSLY VOLATILE, SO CONTINUE TO EXPECT RUN-TO-RUN CHANGES IN
THE NEAR TERM BEFORE SOLUTIONS STABILIZE.
..WEATHER/HAZARDS HIGHLIGHTS
THE PACIFIC SYSTEM AND AMPLIFIED TROUGH LIFTING ACROSS THE WESTERN
U.S. WILL SUPPORT UNSETTLED CONDITIONS FROM CALIFORNIA INTO THE
GREAT BASIN AND CENTRAL/NORTHERN ROCKIES ON WEDNESDAY. MULTIPLE
EMBEDDED SHORTWAVES ROTATING WITHIN AND AROUND THE BASE OF THE
TROUGH WILL BRING PERIODS OF WIDESPREAD LOW ELEVATION RAIN AND
MOUNTAIN SNOW, WITH LOCALLY HEAVY PRECIPITATION POSSIBLE ALONG
FAVORED TERRAIN. 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 AS
THE SYSTEM MOVES ACROSS THE INTERMOUNTAIN WEST INTO THE PLAINS AND
MISSISSIPPI VALLEY THROUGH THE WEEK.
BY THURSDAY, THE DEEPENING PACIFIC SYSTEM EJECTS EASTWARD INTO THE
PLAINS, SETTING THE STAGE FOR LATE WEEK HEAVY RAIN AND SEVERE
WEATHER THREATS AS RICH GULF MOISTURE SURGES NORTHWARD. LARGE SCALE
FORCING COMBINED WITH INCREASING INSTABILITY ALONG AND AHEAD OF A
STRENGTHENING SURFACE LOW AND STRONG COLD FRONT WILL LIKELY RESULT
IN THE DEVELOPMENT OF WIDESPREAD CLUSTERS OF STRONG TO SEVERE
THUNDERSTORMS CAPABLE OF PRODUCING HEAVY RAINFALL AND ISOLATED
FLASH FLOODING. THIS FLOODING THREAT IS HIGHLIGHTED BY A MARGINAL
RISK IN THE DAY 5/THURSDAY ERO, WHICH HAS BEEN EXPANDED IN AREAL
EXTENT WITH THE AFTERNOON UPDATE GIVEN A LARGER QPF FOOTPRINT.
GIVEN INCREASING SOIL MOISTURE FROM PREVIOUS BOUTS OF CONVECTION,
AN UPGRADE TO A SLIGHT RISK IS NOT OUT OF THE QUESTION IN FUTURE
UPDATES.
FARTHER SOUTH, SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE
POSSIBLE ACROSS PARTS OF SOUTHEAST TEXAS AND SOUTHWEST LOUISIANA
ON WEDNESDAY. SUFFICIENT INSTABILITY AND ABOVE NORMAL MOISTURE WILL
SUPPORT ANOTHER RISK FOR LOCALIZED FLASH FLOODING CONCERNS,
CONTINUING FROM DAY 3/TUESDAY. AS A RESULT, DECIDED TO INTRODUCE A
MARGINAL RISK IN THE DAY 4/WEDNESDAY ERO TO ACCOUNT FOR THIS
ISOLATED THREAT.
ELSEWHERE, A RELATIVELY WEAK COLD FRONT WILL CONTINUE TO PUSH
THROUGH THE OHIO VALLEY, MID-ATLANTIC, AND NORTHEAST WEDNESDAY INTO
THURSDAY, BRINGING CHANCES FOR ISOLATED TO SCATTERED SHOWERS.
OTHERWISE, MUCH OF THE DESERT SOUTHWEST AND SOUTHEAST WILL BE
MAINLY DRY NEXT WEEK, BEFORE THE COLD FRONT DROPS INTO THE SOUTHERN
PLAINS/MISSISSIPPI VALLEY BY FRIDAY. AS THE FRONT PUSHES EASTWARD,
SHOWERS AND THUNDERSTORMS MAY DEVELOP FRIDAY INTO THE WEEKEND.
BELOW NORMAL TEMPERATURES OVER THE WESTERN U.S. WILL CONTINUE
THROUGH THE PERIOD WITH TEMPERATURES DROPPING 10-15 DEGREES BELOW
AVERAGE ACROSS CALIFORNIA ON WEDNESDAY BEHIND THE COLD FRONT. AHEAD
OF THE SYSTEM, TEMPERATURES 20-30 DEGREES ABOVE AVERAGE WILL
PERSIST OVER THE CENTRAL U.S. ON WEDNESDAY. AS THE COLD FRONT
PUSHES INTO THE PLAINS BY FRIDAY, ABOVE NORMAL TEMPERATURES
GRADUALLY MOVE EASTWARD BY THE END OF THE WEEK, WHILE BELOW NORMAL
TEMPERATURES WILL SPREAD INTO NORTHERN/CENTRAL PLAINS AND MIDWEST
BY THE WEEKEND. OVER INTO THE WEST, TEMPERATURES WILL BEGIN TO
MODERATE LATE IN THE PERIOD.
MILLER/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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