850
FXUS02 KWBC 180546
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 AM EDT SAT APR 18 2026
VALID 12Z TUE APR 21 2026 - 12Z SAT APR 25 2026
..OVERVIEW
AN ACTIVE SPRING WEATHER PATTERN WILL PERSIST ACROSS CONUS WITH AN
UPPER LEVEL TROUGH/LOW MOVES INTO THE WEST AND SHORTWAVE ENERGY
EJECTING ACROSS THE INTERMOUNTAIN WEST AND INTO THE PLAINS. THE
FRONTAL SYSTEM DOWNSTREAM WILL STRENGTHEN AND PUSH ACROSS THE WEST
INTO CENTRAL U.S. BY MID-TO-LATE NEXT WEEK, WHICH WILL BRING
CHANCES FOR WIDESPREAD PRECIPITATION AND MOUNTAIN SNOW. NOTABLE
TEMPERATURE SWING WILL DEVELOP WITH ABOVE NORMAL TEMPERATURES
PUSHING EASTWARD BY MID-WEEK, AND BELOW AVERAGE TEMPERATURES
RETURNING FOR THE WEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS CONTINUE TO SHOW GOOD AGREEMENT ON THE OVERALL PATTERN WITH
TROUGHING MOVING OFF OF THE EAST COAST, THE RIDGE OVER
WESTERN/CENTRAL U.S., AND THE UPPER-LEVEL TROUGH/LOW OFF THE WEST
COAST. NOTICEABLE DIFFERENCES ARISE LATER IN THE PERIOD ON
THURSDAY, SPECIFICALLY OVER THE NORTHWEST/WEST. CMC, UKMET, AND GFS
SEEMED TO SHOW AGREEMENT WITH THE SHORTWAVE TROUGHS, COMPARED TO
THE ECMWF. GFS ALSO SHOWED HIGHER RUN-TO-RUN VARIABILITY COMPARED
TO THE OTHER MODELS. OVERALL, THE DETERMINISTIC MODELS SEEMED TO
SHOW VARIOUS SOLUTIONS FOR THE PACIFIC UPPER-LEVEL LOW/TROUGH, BUT
THE ENSEMBLE MEANS SEEMED TO HELP ERADICATE SOME OF THE
DIFFERENCES. THEREFORE, A MULTI-MODEL BLEND WAS USED FOR THE FIRST
PORTION OF THE FORECAST, WITH PHASING IN THE ENSEMBLE MEANS TOWARDS
MID-TO- LATE WEEK.
..WEATHER/HAZARDS HIGHLIGHTS
AN UNSTABLE AIRMASS SUPPORTED BY INCREASING RETURN FLOW FROM THE
GULF WILL SUPPORT A BROAD AXIS OF MOISTURE CONVERGENCE ALONG A
FRONTAL BOUNDARY OVER THE GULF, WHICH WILL TRIGGER CONVECTION OVER
PORTIONS OF CENTRAL, SOUTH, AND EAST TEXAS TUESDAY. LOCALLY HEAVY
RAINFALL AND ISOLATED FLASH FLOODING MAY BE POSSIBLE, AND THERE IS
A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THESE AREAS IN THE DAY
4/TUESDAY EXCESSIVE RAINFALL OUTLOOKS (EROS).
MEANWHILE, A PACIFIC FRONTAL SYSTEM WILL CONTINUE TO PUSH EAST INTO
WESTERN U.S. ON TUESDAY, RESULTING IN INCREASING PRECIPITATION
CHANCES ACROSS MUCH OF CALIFORNIA. MODERATE RAINFALL AND MOUNTAIN
SNOW ARE EXPECTED, WITH LOCALLY HEAVY RAINFALL POSSIBLE IN NORTHERN
CALIFORNIA THAT COULD LEAD TO ISOLATED FLOODING CONCERNS. THIS FLOOD
THREAT IS REPRESENTED BY A MARGINAL RISK OF EXCESSIVE RAINFALL FOR
PORTIONS OF NORTHERN CALIFORNIA IN THE DAY4/TUESDAY EROS.
THE PACIFIC SYSTEM AND AMPLIFIED TROUGH WILL MOVE ACROSS THE
INTERMOUNTAIN WEST ON WEDNESDAY AND EMERGE IN THE PLAINS WHILE
STRENGTHENING WEDNESDAY NIGHT INTO THURSDAY. THE SYSTEM IS EXPECTED
TO BRING WIDESPREAD PRECIPITATION AND STRONG GUSTY WINDS ACROSS THE
INTERMOUNTAIN WEST TO THE PLAINS AND MISSISSIPPI VALLEY.
ACCUMULATING MOUNTAIN SNOW WILL BE POSSIBLE ACROSS PORTIONS OF THE
CENTRAL AND NORTHERN ROCKIES AND INTO THE NORTHERN PLAINS. WHILE
IMPACTS SHOULD BE MAINLY CONFINED TO HIGHER ELEVATIONS, SOME TRAVEL
IMPACTS MAY BE POSSIBLE. LOWER ELEVATION RAIN MAY BE MODERATE TO
HEAVY AT TIMES, PARTICULARLY ALONG FAVORED UPSLOPE REGIONS. AS THIS
ENERGY EJECTS INTO THE PLAINS LATE WEEK, CYCLOGENESIS WILL BE
LIKELY, LEADING TO INCREASING CHANCES FOR ORGANIZED CONVECTION.
AS A RELATIVELY COLD WEAK FRONT MOVES THROUGH OHIO VALLEY AND ACROSS
NEW ENGLAND EARLY NEXT WEEK, CHANCES FOR ISOLATED TO SCATTERED
PRECIPITATION WILL BE POSSIBLE FROM TUESDAY INTO THURSDAY. MUCH OF
THE DESERT SOUTHWEST AND SOUTHEAST WILL EXPERIENCE MAINLY DRY
CONDITIONS NEXT WEEK, BUT A COLD FRONT WILL DIP INTO THE SOUTHEAST
BY THE WEEKEND BRINGING CHANCES FOR SHOWERS AND THUNDERSTORMS OVER
THE AREA. IN ADDITION, SOME ISOLATED SHOWERS AND STORMS WILL BE
POSSIBLE FOR SOUTH FLORIDA NEAR A STALLED FRONTAL BOUNDARY THROUGH
THE WEEK.
TEMPERATURES WILL CONTINUE TO TREND BELOW AVERAGE ON TUESDAY FOR
MUCH OF THE EAST COAST, NORTHEAST IN WAKE OF A COLD FRONT. TEXAS
WILL ALSO SEE BELOW AVERAGE TEMPERATURES AS A RESULT OF FORECAST
PRECIPITATION AND CLOUD COVER. AS THE FRONT MOVES INTO WESTERN U.S.,
TEMPERATURES OVER CALIFORNIA WILL DROP 10-20 DEGREES BELOW NORMAL ON
TUESDAY. ABOVE NORMAL TEMPERATURES WILL DEVELOP OVER MUCH OF CENTRAL
AND WESTERN U.S. AHEAD OF THE STRONG FRONTAL SYSTEM, WITH THE
ROCKIES AND PLAINS SEEING HIGH TEMPERATURES RISE TO 15-25 DEGREES
ABOVE AVERAGE. BY MID-WEEK AND FOR THE REMAINDER OF THE PERIOD,
BELOW NORMAL TEMPERATURES WILL SPREAD FROM WEST TO EAST BEHIND THE
WESTERN FRONTAL SYSTEM.
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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