418
FXUS02 KWBC 281913
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
313 PM EDT FRI MAR 28 2025
VALID 12Z MON MAR 31 2025 - 12Z FRI APR 04 2025
...EMERGING HEAVY RAIN AND SEVERE THREAT FOR LOWER MISSISSIPPI,
TENNESSEE, AND OHIO VALLEYS FOR MIDWEEK AND BEYOND...
..OVERVIEW
A PARADE OF SYSTEMS SHOULD BRING PERIODS OF ACTIVE WEATHER TO MUCH
OF THE U.S. NEXT WEEK. A COLD FRONT INTO THE EAST NEXT MONDAY
SHOULD BRING WIDESPREAD RAIN AND THUNDERSTORM CHANCES, WITH SOME
LOCALLY HEAVY RAIN ACROSS THE SOUTH. ANOTHER SYSTEM INTO THE WEST
SHOULD ULTIMATELY LEAD TO A SURFACE LOW EMERGING INTO THE PLAINS
AROUND MIDWEEK AND TRACKING TOWARDS THE GREAT LAKES. WIDESPREAD
MODERATE TO HEAVY RAIN WILL ACCOMPANY THIS SECOND COLD FRONT IN THE
EAST-CENTRAL CONUS, WHILE LATE-SEASON SNOW IS POSSIBLE IN THE
NORTHERN TIER. THE WEST SHOULD STAY RELATIVELY COOL UNDERNEATH OF
ALMOST PERSISTENT TROUGHING, WHILE THE CENTRAL TO EASTERN U.S.
EXPERIENCES PERIODS OF NORMAL TO ABOVE NORMAL TEMPERATURES.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS REASONABLY AGREEABLE AT THE START OF THE MEDIUM
RANGE PERIOD, WITH A SHORTWAVE MOVING THROUGH THE MIDWEST TO
NORTHEAST MONDAY-TUESDAY (THOUGH THE 00Z UKMET WAS A SLOW OUTLIER)
AND AN UPPER LOW OFFSHORE OF THE PACIFIC NORTHWEST. THE LATTER WILL
SEND ENERGY EASTWARD REACHING THE PLAINS BY MIDWEEK, POTENTIALLY
FORMING A WEAK CLOSED LOW, ALONG WITH A REASONABLY STRONG SURFACE
LOW THAT SHOWS TYPICAL TIMING AND PLACEMENT DIFFERENCES AS IT
TRACKS FROM THE CENTRAL U.S. TO THE UPPER GREAT LAKES BY THURSDAY.
UPPER RIDGING IN THE EAST AND MEAN TROUGHING ACROSS THE WEST LOOKS
TO SET UP BY LATER WEEK. THE TROUGHING ACROSS THE WEST HAS SHOWN
THE MOST MODEL DIFFERENCES OVER THE PAST COUPLE OF DAYS. FINALLY
THE 06Z GFS AND NOW THE NEWER 12Z GFS IS SHOWING MORE AGREEMENT
WITH THE LARGER ECMWF/CMC CLUSTER OF GUIDANCE BY AROUND MIDWEEK
(THE 00Z GFS AND OLDER GFS RUNS WERE PULLING SIGNIFICANT AMOUNTS OF
ENERGY AND TROUGHING INTO THE EASTERN PACIFIC AT THAT TIME).
HOWEVER, THE 00Z ECMWF APPEARED TO PULL A DIFFERENT SHORTWAVE
SOUTHWARD ALONG THE WEST COAST THURSDAY-FRIDAY, WHICH REALLY ONLY
THE PANGU AI/ML MODEL AGREED WITH--OTHER AI MODELS AND THE CMC
SHOWED THE TROUGH AXIS FARTHER EAST. SO DID NOT FAVOR THE 00Z EC AS
MUCH DURING THE LATE PERIOD.
THUS THE WPC FORECAST WAS BASED ON A BLEND INITIALLY FAVORING THE
00Z ECMWF WITH LESSER PROPORTIONS OF THE 06Z GFS AND 00Z CMC EARLY
IN THE PERIOD. AS THE PERIOD PROGRESSED, LESSENED THE PROPORTION OF
DETERMINISTIC MODELS IN FAVOR OF THE ENSEMBLE MEANS TO HALF DAY 6
AND MORE DAY 7 AS SPREAD INCREASED. NOTABLE EDITS TO THE NBM
INCLUDED LOWERING QPF IN THE WEST WHERE THE OLDER GFS RUNS THAT
WERE NOT FAVORED SEEMED TO BE CONTRIBUTING HEAVY QPF INTO THE BLEND
WHILE THE EC/CMC AND THEIR MEANS SHOWED LESS. QPF INCREASED FROM
CONTINUITY IN THE EAST-CENTRAL U.S. AS MODELS STARTED TO BE MORE
AGREEABLE WITH HEAVY AMOUNTS FOR THE LATTER HALF OF NEXT WEEK.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT MOVING INTO THE EAST SHOULD ALLOW FOR WIDESPREAD RAIN
AND THUNDERSTORMS ACROSS MUCH OF THE EASTERN SEABOARD ON MONDAY.
THE BEST CHANCE FOR LOCALLY HEAVY TO EXCESSIVE RAINFALL SHOULD BE
OVER PARTS OF THE SOUTHEAST WHERE MORE INSTABILITY WILL ALLOW FOR
HEAVIER RAIN RATES, SO A MARGINAL RISK REMAINS IN PLACE FOR THE DAY
4/MONDAY EXCESSIVE RAINFALL OUTLOOK. LOCALLY HEAVY RAIN MAY ALSO
OCCUR FARTHER NORTH FROM THE APPALACHIANS TO MID-ATLANTIC AND
NORTHEAST. THE STORM PREDICTION CENTER ALSO SUGGESTS STRONG TO
SEVERE WEATHER IS POSSIBLE FROM THE SOUTHEAST INTO THE MID-
ATLANTIC AS WELL ON MONDAY.
EXPECT MULTIPLE SYSTEMS TO BRING RAIN AND HIGHER ELEVATION SNOW TO
THE WEST DURING THE PERIOD. THE BEST PRECIPITATION FOCUS LOOKS TO
BE ACROSS NORTHERN CALIFORNIA ON MONDAY, AND A MARGINAL RISK
REMAINS IN PLACE FOR COASTAL REGIONS INTO FAR SOUTHWEST OREGON FOR
THE DAY 4/MONDAY ERO WITH A WEAK ATMOSPHERIC RIVER. PRECIPITATION
WITH SOME HIGHER ELEVATION SNOW WILL SPREAD THROUGH THE
INTERMOUNTAIN WEST AND ROCKIES MONDAY-TUESDAY, WHILE THE PATTERN
ALSO SUPPORTS HIGH WINDS FOCUSED FROM THE CENTRAL GREAT BASIN INTO
THE CENTRAL ROCKIES. AS THE UPPER TROUGH IN THE WEST RELOADS INTO
MID AND LATE NEXT WEEK, IT 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 HEAVY
RAINFALL IS ALSO A CONCERN. THE LOW IS FORECAST TO MOVE
NORTHEASTWARD THURSDAY-FRIDAY BUT LEAVE A WAVY FRONT BEHIND ACROSS
THE MID-SOUTH TO OHIO VALLEY, CAUSING LIKELY MULTIPLE ROUNDS OF
HEAVY RAIN OVER SIMILAR AREAS, ENHANCING FLOODING CONCERNS.
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. MEANWHILE
SOME MODEST RAIN AND SNOW COULD CONTINUE ACROSS THE WEST
THROUGHOUT NEXT WEEK, THOUGH WITH RAPIDLY INCREASING UNCERTAINTY IN
THE DETAILS AFTER EARLY NEXT WEEK.
THE WARM SECTOR AHEAD OF THE FRONT CROSSING THE EASTERN HALF OF
THE COUNTRY INTO MONDAY WILL FEATURE WELL ABOVE NORMAL
TEMPERATURES. EXPECT PLUS 10-20F ANOMALIES FOR HIGHS AND UP TO PLUS
20-25F ANOMALIES FOR MORNING LOWS. NEAR TO BELOW NORMAL READINGS
WILL PROGRESS EASTWARD BEHIND THE EASTERN U.S. FRONT, WITH
PRECIPITATION KEEPING SOME NORTHERN PLAINS TO GREAT LAKES LOCATIONS
5-10F OR SO BELOW NORMAL FOR HIGHS INTO TUESDAY. TEMPERATURES MAY
REBOUND BACK ABOVE NORMAL OVER THE SOUTHERN HALF OF THE PLAINS ON
WEDNESDAY WITH THE WARMING TREND SPREADING BACK INTO THE EAST
THEREAFTER. PERIODS OF UNSETTLED WEATHER WILL KEEP THE DIURNAL
SPREAD OVER THE WEST COAST STATES MORE NARROW THAN USUAL, WITH COOL
HIGHS AND NEAR NORMAL LOWS.
TATE/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
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