984
FXUS02 KWBC 130659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM 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 12/18Z
GFS AND 12Z ECMWF AND CMC COULD BE USED TO DEPICT THIS PATTERN.
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 HAVE BEEN PERSISTENTLY FAST IN
LIFTING THE TROUGH EAST COMPARED TO THE SLOWER ECMWF. EVEN AROUND
MONDAY THIS LED TO MODEL DIFFERENCES IN HOW QUICKLY PRECIPITATION
MOVES OFF THE EAST COAST, AND THEN POSITIONING DIFFERENCES IN THE
PLACEMENT OF A RESULTING UPPER LOW IN THE ATLANTIC TOWARD MIDWEEK.
AN INTERMEDIATE SOLUTION LIKE THE ENSEMBLE MEANS AND EVEN THE CMC
SEEMED MORE REASONABLE. MEANWHILE AS THE OTHER TROUGH MOVES INTO
THE WESTERN AND THEN CENTRAL U.S., THE 12Z ECMWF ALONG WITH MANY OF
ITS ENSEMBLE MEMBERS HAVE BEEN SLOW OUTLIERS WITH ITS PROGRESSION
EASTWARD. 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 GAVE CONFIDENCE
TO LEAN AWAY FROM THE SLOW ECMWF/EC MEAN SOLUTIONS. FOR THE
FORECAST BLEND, LEANED MORE TOWARD THE 18Z GFS AND CMC AND THEIR
ENSEMBLE MEANS BY THE LATE PERIOD. THE NEWER 00Z ECMWF IS NOW
FASTER AND THUS IN BETTER ALIGNMENT WITH THIS LARGER GUIDANCE
CLUSTER. HOWEVER, THE 00Z GFS IS SHALLOWER WITH THE TROUGH AND
PROGRESSES IT EAST SO QUICKLY THAT THE SURFACE LOW AND
PRECIPITATION ARE FARTHER NORTHEAST THAN ITS PREVIOUS FAVORED RUN.
..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. THE DAY 4/SUNDAY ERO MAINTAINS A 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 HEAVY. 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 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 LOOKS TO
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, A 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.
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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