577
FXUS02 KWBC 131854
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 PM EDT THU MAR 13 2025
VALID 12Z SUN MAR 16 2025 - 12Z THU MAR 20 2025
...HEAVY RAIN AND SEVERE WEATHER POSSIBLE FOR THE EAST COAST SUNDAY...
..ATMOSPHERIC RIVER FOR OREGON AND NORTHERN CALIFORNIA SUNDAY
..OVERVIEW
AS THE MEDIUM RANGE PERIOD BEGINS SUNDAY, A COLD FRONT WITH
REINFORCING FRONTS BEHIND IT WILL SWEEP ACROSS THE EAST. WIDESPREAD
THUNDERSTORMS ARE LIKELY AHEAD OF THE PRIMARY FRONT, WHICH COULD
BE SEVERE AND HAVE EMBEDDED HEAVY RAIN CAUSING FLOODING CONCERNS.
WARMER THAN NORMAL TEMPERATURES IN THE EAST AHEAD OF THE FRONT WILL
COOL TOWARD NORMAL BEHIND IT, BUT TEMPERATURES ARE FORECAST TO
WARM BACK UP IN THE CENTRAL AND THEN EASTERN U.S. AS THE WEEK
PROGRESSES. MEANWHILE IN THE WEST, AN ATMOSPHERIC RIVER COULD CAUSE
LOCALLY HEAVY RAIN AND HIGHER ELEVATION SNOW ON SUNDAY AHEAD OF AN
UPPER TROUGH. AS THIS UPPER TROUGH MOVES MOVES ACROSS THE WESTERN
AND CENTRAL U.S., RAIN AND SNOW IS FORECAST TO SPREAD THROUGH THE
INTERIOR WEST MONDAY-TUESDAY AND INTO THE CENTRAL AND EAST-CENTRAL
U.S. TUESDAY-WEDNESDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT EARLY NEXT WEEK WITH THE
SYNOPTIC SCALE PATTERN THAT CONSISTS OF AN UPPER TROUGH AXIS MOVING
EASTWARD FROM THE MISSISSIPPI VALLEY INTO THE EAST, ANOTHER TROUGH
TRACKING FROM THE EASTERN PACIFIC INTO THE INTERIOR WEST, AND
UPPER RIDGING IN BETWEEN. A MULTI-MODEL BLEND INCLUDING THE LATEST
RUNS OF THE GFS, ECMWF, CMC, AND UKMET WAS UTILIZED.
BY MONDAY-TUESDAY AND BEYOND, BOTH THE WESTERN AND EASTERN TROUGHS
SHOW SOME SPREAD REGARDING HOW QUICKLY THEY PROGRESS EASTWARD.
NEAR THE EAST COAST, GFS RUNS REMAIN A BIT FAST WITH ADDITIONAL
POSITIONING DIFFERENCES IN THE PLACEMENT OF A CUTOFF UPPER LOW IN
THE ATLANTIC TOWARD MIDWEEK. MEANWHILE AS THE OTHER TROUGH MOVES
INTO THE WESTERN AND THEN CENTRAL U.S., THE ECMWF ALONG WITH MANY
OF ITS ENSEMBLE MEMBERS CONTINUE TO BE SLOW OUTLIERS WITH ITS
PROGRESSION EASTWARD. THE UKMET IS ALSO ON THE SLOW SIDE BEFORE IT
PHASES OUT AFTER DAY 5. GFS AND CMC RUNS AND THEIR ENSEMBLE MEMBERS
TENDED TO BE FASTER IN SWEEPING THE TROUGH TOWARD THE CENTRAL U.S.
AS WELL AS THE ASSOCIATED SURFACE LOW. THE EC- BASED AI/ML MODELS
WERE UNIFORMLY FASTER THAN THE CONTROL 12Z ECMWF, WHICH CONTINUED
TO GIVE CONFIDENCE TO LEAN AWAY FROM THE SLOWER ECMWF/EC MEAN
SOLUTIONS. WPC LEANED MORE HEAVILY ON THE GFS AND GEFS/NAEFS RUNS
LATER IN THE PERIOD, MAINTAINING GOOD CONTINUITY WITH THE PREVIOUS
WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
THE EASTERN SEABOARD IS FORECAST TO SEE WIDESPREAD CONVECTION ON
SUNDAY AS MOISTURE STREAMS IN AHEAD OF THE COLD FRONTS. SEVERE
THUNDERSTORMS ARE POSSIBLE FROM THE MID-ATLANTIC TO CAROLINAS AND
SOUTHEAST PER THE STORM PREDICTION CENTER. LOCALLY HEAVY RAINFALL
IS ALSO POSSIBLE, WITH THE DAY 4/SUNDAY ERO MAINTAINING A BROAD
MARGINAL RISK STRETCHING ACROSS MUCH OF THE EASTERN SEABOARD. THERE
IS SOME UNCERTAINTY IN HOW QUICKLY THE COLD FRONT MOVES EASTWARD
INTO THE ATLANTIC OFF THE SOUTHEAST COAST, BUT HEAVY RAIN WITH HIGH
RATES IS LIKELY AHEAD OF IT. MEANWHILE FARTHER NORTH IN THE
NORTHERN MID- ATLANTIC AND NORTHEAST, MOISTURE ANOMALIES ARE
GENERALLY OVER THE 95TH PERCENTILE AND SOME MODEST INSTABILITY IS
IN PLACE, SO RAIN RATES FOR THE REGION COULD BE LOCALLY HIGH. ALL
THIS PROVIDES CONTINUED SUPPORT FOR A MARGINAL RISK BUT FUTURE
ADJUSTMENTS CERTAINLY COULD BE NECESSARY. THE QUICK MOVEMENT OF THE
HEAVY RAIN RATES EASTWARD AHEAD OF THE FRONT COULD LIMIT FLOODING
POTENTIAL TO STAY BELOW SLIGHT RISK LEVELS. RAIN AND STORMS MAY
CONTINUE INTO MONDAY FOR COASTAL AREAS OF THE NORTHEAST BEFORE
MOVING AWAY.
IN THE WEST, AN ATMOSPHERIC RIVER OF MODERATE STRENGTH IS FORECAST
TO IMPACT OREGON AND NORTHERN CALIFORNIA ON SUNDAY AND PRODUCE
HEAVY PRECIPITATION (LOWER ELEVATION RAIN AND HIGHER ELEVATION
SNOW). SOME LOCALIZED RAIN RATES OF OVER AN INCH PER HOUR ARE
LIKELY, AND THE AR MAY STALL BRIEFLY NEAR THE CA/OR BORDER.
CONTINUE TO DELINEATE A MARGINAL RISK IN THE DAY 4/SUNDAY ERO, BUT
HELD OFF ON ANY SLIGHT RISK AS THE AREA LIKELY TO RECEIVE THE
HEAVIEST RAIN IS NOT VERY SENSITIVE TO FLOODING. THE AR SHOULD
WEAKEN AS IT PUSHES INTO CENTRAL AND SOUTHERN CALIFORNIA LATER
SUNDAY AND INTO MONDAY, WHICH SHOULD PRECLUDE TOO MANY FLOODING
ISSUES OVER RECENT BURN SCARS. HEAVY SNOW MAY PILE UP OVER HIGHER
ELEVATIONS OF THE CASCADES, SIERRA NEVADA, AND THE INTERIOR WEST
AND ROCKIES INTO EARLY NEXT WEEK AS PRECIPITATION CHANCES GRADUALLY
SHIFT EAST. WHILE THE DETAILS ARE STILL COMING INTO FOCUS, ANOTHER
LOW PRESSURE SYSTEM IS FORECAST TO STRENGTHEN IN THE CENTRAL
PLAINS BY TUESDAY (THOUGH WEAKER THAN THE SHORT RANGE LOW) AND MOVE
EAST OR NORTHEAST. THIS LOW AND ITS FRONTAL BOUNDARIES WILL ALLOW
FOR SOME PRECIPITATION TO SPREAD GENERALLY ACROSS THE
CENTRAL/NORTHERN PLAINS INTO THE GREAT LAKES, WITH SOME MIXED
PRECIPITATION AND/OR SNOW POSSIBLE NORTHWEST OF THE SYSTEM TRACK.
RAIN IS FORECAST TO DEVELOP IN THE EAST-CENTRAL U.S. BY MIDWEEK.
ANOTHER THREAT AS THE UPPER TROUGH PUSHES EAST THROUGH THE WESTERN
AND CENTRAL U.S. WILL BE HIGH WINDS. WINDS IN THE SOUTHERN ROCKIES
AND SOUTHERN PLAINS COULD ONCE AGAIN CAUSE FIRE DANGER MONDAY-
TUESDAY.
ABOVE NORMAL TEMPERATURES ARE LIKELY ACROSS THE EASTERN THE U.S.
ON SUNDAY, WITH GREATEST ANOMALIES OF 20-30 DEGREES WARMER THAN
AVERAGE FOR HIGHS LIKELY IN THE MID-ATLANTIC AND NORTHEAST. EXPECT
MORNING LOWS TO BE EVEN MORE ABOVE AVERAGE, WELL INTO THE 50S AND
60S, WHICH COULD SET RECORDS FOR WARM MINS--IF THE LOCATIONS DO NOT
HAVE THOSE TEMPERATURES FALL LOWER BEFORE THE CALENDAR DAY AFTER
THE COLD FRONTAL PASSAGE. WHILE TEMPERATURES COOL IN THE EAST FOR
MONDAY, MILDER THAN AVERAGE TEMPERATURES ARE FORECAST TO REBUILD IN
THE CENTRAL U.S., SPREADING INTO THE EAST BY TUESDAY-WEDNESDAY
UNDERNEATH UPPER RIDGING. TEMPERATURES WILL ONCE AGAIN COOL FROM
WEST TO EAST BEHIND ANOTHER COLD FRONT WEDNESDAY-THURSDAY.
MEANWHILE, PERIODS OF TROUGHING ACROSS THE WEST WILL PRODUCE BELOW
NORMAL TEMPERATURES ON AVERAGE, LIKELY MOST BELOW AVERAGE ON
TUESDAY-WEDNESDAY. HIGHS SHOULD GENERALLY BE A BIT MORE BELOW
NORMAL COMPARED TO LOW TEMPERATURES GIVEN CLOUDS AND PRECIPITATION.
SANTORELLI/TATE
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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