456
FXUS02 KWBC 181933
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
333 PM 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 THE CONUS
NEXT WEEK AS A POTENT MID/UPPER LEVEL LOW SWINGS ACROSS NORTHERN
CALIFORNIA AND THE PACIFIC NORTHWEST BEFORE EJECTING EASTWARD INTO
THE NORTHERN PLAINS. THIS SYSTEM WILL BRING STRONG WINDS AND
WIDESPREAD PRECIPITATION, INCLUDING THE POTENTIAL FOR MODERATE TO
HEAVY RAIN AND MOUNTAIN SNOW. HEAVY RAIN AND SEVERE WEATHER THREATS
THEN EXPAND INTO THE CENTRAL U.S. BY LATE WEEK AS A SURFACE LOW
STRENGTHENS AND RICH MOISTURE IS DRAWN NORTHWARD FROM THE GULF.
THIS ACTIVE PATTERN WILL FOSTER SIGNIFICANT TEMPERATURE SWINGS,
WITH ABOVE NORMAL TEMPERATURES PUSHING FROM THE CENTRAL U.S.
EASTWARD, WHILE BELOW NORMAL TEMPERATURES RETURN ACROSS THE WEST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE CONTINUES TO HAVE A RELATIVELY GOOD HANDLE ON
THE LARGE SCALE PATTERN THROUGH MOST OF THE MEDIUM RANGE PERIOD.
MOST OF THE UNCERTAINTY STEMS FROM THE EVOLUTION OF SMALLER SCALE
WAVES WITHIN AND ROTATING AROUND THE INLAND PENETRATING MID/UPPER
LEVEL LOW/TROUGH ACROSS THE WESTERN/CENTRAL U.S., WITH THESE
DETAILS AFFECTING SURFACE LOW PLACEMENT AND DEVELOPMENT AND
SENSIBLE WEATHER. FORECAST PREFERENCES LEANED MORE HEAVILY TOWARDS
THE ECMWF AND EC-AIFS GIVEN SLIGHTLY BETTER RUN-TO-RUN STABILITY,
BUT MOST WEIGHT WAS PLACED ON THE ECMWF AND GEFS ENSEMBLE MEANS,
PARTICULARLY FOR DAYS 5 AND 6. THIS COMPOSITE BLEND SEEMED TO
PROVIDE A GOOD FOUNDATION OF LARGE SCALE FEATURES WHILE STILL
MAINTAINING AN ACCEPTABLE LEVEL OF FINER SCALE DETAILS.
..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 SOUTHEAST TX TUESDAY. LOCALLY HEAVY RAINFALL AND
ISOLATED FLASH FLOODING MAY BE POSSIBLE, AND THERE REMAINS A
MARGINAL RISK OF EXCESSIVE RAINFALL FOR THIS AREA IN THE DAY
4/TUESDAY EXCESSIVE RAINFALL OUTLOOK (ERO).
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 ALSO REPRESENTED BY A MARGINAL RISK OF EXCESSIVE
RAINFALL FOR PORTIONS OF NORTHERN CALIFORNIA IN THE DAY 4/TUESDAY
ERO.
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, A STRONG DEVELOPING
SURFACE LOW IS LIKELY TO LEAD TO INCREASING CHANCES FOR ORGANIZED
CONVECTION AND SEVERE WEATHER.
AS A RELATIVELY WEAK COLD FRONT MOVES THROUGH THE OHIO VALLEY,
MID- ATLANTIC, AND NORTHEAST EARLY NEXT WEEK, CHANCES FOR ISOLATED
TO SCATTERED SHOWERS WILL BE POSSIBLE FROM TUESDAY INTO THURSDAY.
MUCH OF THE DESERT SOUTHWEST AND SOUTHEAST WILL BE MAINLY DRY NEXT
WEEK, BUT A COLD FRONT WILL DIP INTO THE SOUTHEAST BY THE WEEKEND
BRINGING CHANCES FOR SHOWERS AND THUNDERSTORMS. 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 IN THE WAKE OF A COLD FRONT. TEMPERATURES IN TEXAS
WILL ALSO BE BELOW NORMAL AS A RESULT OF PRECIPITATION AND CLOUD
COVER. BELOW NORMAL TEMPERATURES WILL SPILL INTO CALIFORNIA AND
MUCH OF THE WEST AS THE STRONG MID/UPPER LEVEL LOW PUSHES INLAND.
ABOVE NORMAL TEMPERATURES WILL DEVELOP OVER MUCH OF CENTRAL AND
WESTERN U.S. AHEAD OF THIS STRONG SYSTEM, WITH THE ROCKIES AND
PLAINS SEEING HIGH TEMPERATURES RISE TO 20-30 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.
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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