081
FXUS02 KWBC 290634
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 AM EDT SAT MAR 29 2025
VALID 12Z TUE APR 01 2025 - 12Z SAT APR 05 2025
...EMERGING HEAVY RAIN AND SEVERE THREAT FOR LOWER MISSISSIPPI,
TENNESSEE, AND OHIO VALLEYS FOR MIDWEEK AND BEYOND...
..OVERVIEW
THE MEDIUM RANGE UPPER PATTERN SHOULD TREND MORE AMPLIFIED MID TO
LATE NEXT WEEK AND INCREASINGLY ACTIVE. A SYSTEM INTO THE WEST
AROUND TUESDAY SHOULD ULTIMATELY LEAD TO A SURFACE LOW EMERGING
INTO THE PLAINS AROUND MIDWEEK AND TRACKING TOWARDS THE GREAT
LAKES. A BUILDING UPPER RIDGE OVER THE WESTERN ATLANTIC INTO THE
GULF SHOULD KEEP THE ASSOCIATED FRONTAL BOUNDARY FROM MAKING MUCH
PROGRESS, ESPECIALLY LATER IN THE WEEK. THIS SETS THE STAGE FOR A
MULTI-DAY HEAVY RAIN AND SEVERE WEATHER THREAT FROM THE LOWER
MISSISSIPPI INTO THE OHIO VALLEY ALONG THIS BOUNDARY. SOME LATE-
SEASON SNOW MAY BE POSSIBLE NORTH OF THIS SYSTEM FROM THE NORTHERN
PLAINS TO GREAT LAKES. THE WEST SHOULD STAY RELATIVELY COOL
UNDERNEATH OF PERSISTENT TROUGHING, WHILE ABOVE NORMAL TEMPERATURES
PROGRESS FROM THE CENTRAL U.S. AND MIDWEST, EVENTUALLY SETTLING
LATE WEEK ACROSS THE SOUTHEAST AND INTO THE MID-ATLANTIC.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS RELATIVELY AGREEABLE ON THE LARGE SCALE PATTERN
NEXT WEEK INTO THE WEEKEND, BUT STILL VERY UNCERTAIN WITH SOME OF
THE DETAILS, WHICH COULD HAVE SENSIBLE WEATHER IMPACTS. A SHORTWAVE
EXITING THE EAST ON TUESDAY WILL BE REPLACED BY A BUILDING RIDGE
OVER THE WESTERN ATLANTIC TO THE GULF THAT LASTS INTO NEXT WEEKEND.
THIS SHOULD HELP AMPLIFY AND RELOAD TROUGHING OVER THE WEST EARLY
TO MID WEEK. THE GUIDANCE SHOWS BETTER CONSISTENCY IN THIS
EVOLUTION COMPARED TO YESTERDAY, BUT STILL CONSIDERABLE UNCERTAINTY
IN THE DETAILS OF MULTIPLE PIECES OF ENERGY WITHIN THE OVERALL
TROUGH. A LEADING SHORTWAVE MAY BRIEFLY CLOSE OFF A COMPACT LOW
THAT INDUCES SURFACE CYCLOGENESIS ACROSS THE CENTRAL U.S. THAT
TRACKS INTO THE GREAT LAKES. ENERGY WILL ALLOW FOR THE WESTERN U.S.
TROUGH TO RELOAD LATE WEEK WITH A STATIONARY SURFACE BOUNDARY
SETTING UP BETWEEN THE SOUTHEAST RIDGE AND WESTERN TROUGH. THERE
ARE SUBTLE DIFFERENCES IN THE EXACT PLACEMENT OF THIS FRONT THOUGH,
WHICH HAS SIGNIFICANT IMPLICATIONS ON THE AXIS OF HEAVY RAINFALL
EXPECTED TO ACCOMPANY THIS. THE 18Z/MAR 28 GFS WAS A BIT FARTHER
EAST WITH THE OVERALL EVOLUTION, BUT THE NEW 00Z RUN (AVAILABLE
AFTER FORECAST GENERATION TIME) WAS MORE IN LINE WITH CONSENSUS.
UPPER RIDGING UPSTREAM FROM THIS MAY SNEAK BACK INTO THE NORTHWEST
NEXT WEEKEND.
THE WPC FORECAST WAS ABLE TO UTILIZE A GENERAL DETERMINISTIC MODEL
BLEND FEATURING THE GFS, ECMWF, CMC, AND UKMET THROUGH DAY 4. BY
DAY 5, BEGAN INCORPORATING SOME ENSEMBLE MEAN GUIDANCE TO HELP
TEMPER THE DETAIL DIFFERENCES. TRENDED DAYS 6 AND 7 TO A 60/40
ENSEMBLE MEAN/DETERMINISTIC GUIDANCE SPLIT. THIS APPROACH
MAINTAINED RELATIVELY GOOD AGREEMENT WITH THE PREVIOUS WPC FORECAST
(THROUGH DAY 6).
..WEATHER/HAZARDS HIGHLIGHTS
EXPECT A SERIES OF SHORTWAVES TO BRING RAIN AND HIGHER ELEVATION
SNOW TO THE WEST NEXT WEEK. AN ATMOSPHERIC RIVER SHOULD BE SINKING
SOUTHWARD ALONG THE CALIFORNIA COAST BY TUESDAY, BUT SOME LINGERING
PRECIPITATION ALONG THE NORTHWEST COAST MAY BRING AT LEAST LOCALLY
MODERATE TO HEAVY RAINFALL. OPTED TO NOT INCLUDE A MARGINAL RISK
ON THE DAY 4 ERO TONIGHT GIVEN THE BETTER DYNAMICS AND MOISTURE
ANOMALIES WERE SOUTH. PRECIPITATION WILL SPREAD THROUGH THE
INTERMOUNTAIN WEST AND ROCKIES INTO TUESDAY, WHILE THE PATTERN MAY
ALSO SUPPORT HIGH WINDS FOCUSED FROM THE CENTRAL GREAT BASIN INTO
THE CENTRAL ROCKIES. MODERATE TO HEAVY SNOW MAY FALL IN PARTS OF
THE SIERRA NEVADA.
OVERALL PATTERN AMPLIFICATION AND A LEADING SHORTWAVE WILL SUPPORT
A SURFACE LOW PRESSURE SYSTEM FORMING IN THE CENTRAL U.S. BY
WEDNESDAY WITH WIDESPREAD THUNDERSTORMS ACROSS THE EAST- CENTRAL
U.S. IN ITS WARM SECTOR. SPC INDICATES ANOTHER ROUND OF SEVERE
WEATHER FROM THE SOUTH-CENTRAL U.S. INTO THE MID- SOUTH AND OHIO
VALLEY ON WEDNESDAY (AND POSSIBLY BEYOND). POTENTIAL FOR A MULTI-
DAY HEAVY RAINFALL EVENT IS INCREASING AS A WAVY BOUNDARY SITS OVER
THE OHIO VALLEY TO LOWER MISSISSIPPI VALLEY INTO NEXT WEEKEND.
AMPLE MOISTURE AND INSTABILITY ALONG AND AHEAD OF THE FRONT SHOULD
SUPPORT TRAINING THUNDERSTORMS AND HIGH RAIN RATES. AT THIS POINT,
THE DAY 5/WEDNESDAY ERO INDICATES A SLIGHT RISK FROM ARKANSAS INTO
SOUTHERN INDIANA AND SOUTHWEST OHIO, SURROUNDED BY A BROAD MARGINAL
RISK TO ACCOUNT FOR UNCERTAINTY. GIVEN THE PATTERN, IT'S ENTIRELY
POSSIBLE A MODERATE RISK MAY EVENTUALLY BE NEEDED IN SUBSEQUENT
UPDATES, BUT THERE IS STILL SOME UNCERTAINTY IN EXACTLY WHERE THE
SURFACE BOUNDARY SETS UP. ADDITIONALLY, SOME APRIL SNOW IS LIKELY
ON THE BACKSIDE OF THE LOW ACROSS THE NORTHERN PLAINS AND UPPER
MIDWEST TUESDAY- WEDNESDAY AND SPREADING INTO THE INTERIOR
NORTHEAST WEDNESDAY- THURSDAY. SOME MODEST RAIN AND SNOW COULD ALSO
CONTINUE ACROSS THE WEST THROUGHOUT NEXT WEEK, THOUGH WITH RAPIDLY
INCREASING UNCERTAINTY IN THE DETAILS AFTER EARLY NEXT WEEK.
ABOVE NORMAL TEMPERATURES WILL SHIFT FROM THE CENTRAL/SOUTHERN
PLAINS ON TUESDAY INTO THE MIDWEST ON WEDNESDAY, AND SETTLE ACROSS
MUCH OF THE EASTERN U.S. THURSDAY AND BEYOND. DAYTIME HIGHS 10 TO
20 DEGREES ABOVE NORMAL ARE POSSIBLE. MEANWHILE, THE WEST SHOULD
TREND AND STAY COOLER UNDERNEATH UPPER TROUGHING THROUGH FRIDAY. BY
NEXT WEEKEND, TEMPERATURES MAY MODERATE SOMEWHAT AND SHIFT
SLIGHTLY EAST AS EASTERN PACIFIC UPPER RIDGING MOVES IN TOWARDS THE
WEST COAST.
SANTORELLI
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page