103
FXUS02 KWBC 071910
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 PM EST FRI MAR 7 2025
VALID 12Z MON MAR 10 2025 - 12Z FRI MAR 14 2025
..WETTER/SNOWIER PATTERN EMERGING FOR THE WEST NEXT WEEK
..OVERVIEW
AS THE MEDIUM RANGE PERIOD BEGINS MONDAY, A COUPLE OF SOUTHERN
STREAM UPPER/SURFACE LOWS WILL SURROUND A CENTRAL U.S. UPPER RIDGE.
ONE OVER THE SOUTHEAST WILL LIKELY PRODUCE SOME RAIN THROUGH THE
DAY ON MONDAY BEFORE PULLING AWAY, WHILE ANOTHER IN THE EASTERN
PACIFIC SPREADS LIGHT TO MODERATE PRECIPITATION FROM SOUTHERN
CALIFORNIA INTO THE SOUTHWEST AS IT MOVES INLAND. THE LATTER WILL
END UP WITH A CONSOLIDATING SURFACE LOW IN THE SOUTH-CENTRAL PLAINS
BY MIDWEEK AND SOME GENERALLY LIGHT TO MODERATE PRECIPITATION IN
THE EASTERN HALF OF THE U.S. WEDNESDAY-THURSDAY. THEN THERE IS GOOD
MODEL AGREEMENT FOR A DEEP AND PHASED UPPER TROUGH TO PIVOT
THROUGH THE EASTERN PACIFIC MIDWEEK INTO THE WEST LATER WEEK ALONG
WITH AN ATMOSPHERIC RIVER, WHICH WILL BRING WIDESPREAD RAIN AND
HIGHER ELEVATION SNOW ACROSS THE WEST. BY THE END OF THE PERIOD,
MODEL AGREEMENT REMAINS REMARKABLY GOOD FOR A STRONG SURFACE LOW
TO DEVELOP ACROSS THE CENTRAL PLAINS IN THE LEE OF THE COLORADO
ROCKIES. FARTHER EAST, BOUTS OF UPPER RIDGING WILL ALLOW FOR ABOVE
NORMAL TEMPERATURES ACROSS THE CENTRAL AND EASTERN U.S. FOR MUCH OF
NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
OVERALL, THE LATEST MODEL GUIDANCE CONTINUES TO HAVE A GOOD HANDLE
OF THE LARGE SCALE PATTERN OVER THE NEXT 3 TO 7 DAYS. HOWEVER,
VARYING DEGREES OF SPREAD STILL REMAIN WITHIN SOME SMALLER SCALE
FEATURES. STARTING WITH THE SHORTWAVE/SMALL UPPER LOW AND SURFACE
LOW MOVING THROUGH THE SOUTHEAST, GFS TRENDS FROM LAST NIGHT AND
THE DAYS PRIOR CONTINUED TODAY, SHOWING A SLOWER, STRONGER, AND
MORE COMPACT SURFACE LOW JUST OFF THE COAST OF THE SOUTHEAST U.S.
(THOUGH STILL ON THE FASTER SIDE OF THE OTHERWISE FAIRLY WELL
CLUSTERED GUIDANCE) BY 12Z MONDAY. MODELS HAVE ALSO COME INTO
BETTER AGREEMENT WITH THE QPF FOOTPRINT IN THE DEFORMATION AXIS OF
THE SURFACE LOW, DEPICTING STEADY MODERATE TO BORDERLINE HEAVY
PRECIPITATION FROM GEORGIA TO THE CAROLINAS THROUGH MONDAY, ENDING
BY EARLY TUESDAY. IN THE WEST EARLY NEXT WEEK, THE 12Z RUNS FROM
THE CMC AND UKMET CONTINUED THEIR TRENDS FROM 00Z. THESE MODELS
DEPICTED A SLOWER UPPER LOW EVOLUTION WHICH MORE FAVORABLY MATCHED
THE EC/GFS CONSENSUS. ELSEWHERE, SHALLOW SHORTWAVES IN THE NORTHERN
STREAM ALSO SHOWED SOME MODEL SPREAD THAT NECESSITATED TYPICAL
CHANGES TO THE ASSOCIATED FRONTAL AND SURFACE LOW TIMING.
INTO WEDNESDAY AND THURSDAY, MODELS SHOW REASONABLE AGREEMENT IN
THE TROUGH TO MOVE FROM THE SOUTHWEST INTO THE SOUTHERN/CENTRAL
PLAINS AND THE TENNESSEE VALLEY AND VICINITY. A SURFACE LOW SHOULD
CONSOLIDATE IN THE SOUTH-CENTRAL PLAINS BY WEDNESDAY BUT THERE IS
SPREAD IN ITS TRACK AFTER THAT. ALSO COMPLICATING THINGS ARE
DIFFERENCES AMONG MODELS WITH RESPECT TO THE STRENGTH AND TRACK OF
A NORTHERN STREAM SHORTWAVE SCOOTING ACROSS NORTHERN MINNESOTA BY
12Z WEDNESDAY. THE ECMWF REMAINS THE MOST BULLISH WITH THIS
FEATURE, WHICH ULTIMATELY DEVELOPS A STRONGER SURFACE LOW NEAR THE
GREAT LAKES BY THURSDAY. MEANWHILE MODEL AGREEMENT REMAINS GOOD
FOR TROUGHING TO MAKE ITS WAY FROM THE EASTERN PACIFIC WEDNESDAY
INTO THE WEST COAST THURSDAY. THE 00Z ECMWF AND UKMET WERE QUITE
AGGRESSIVE IN SHOWING A CLOSED LOW WITHIN THE UPPER TROUGH BY
WEDNESDAY OFFSHORE OF THE PACIFIC NORTHWEST AND DEEP WITH THE
ASSOCIATED SURFACE LOW. THE 12Z RUNS OF THE THOSE MODELS CONTINUED
TO BE BULLISH, AND THE 12Z GFS JUMPED ON BOARD AS WELL. WILL HAVE
TO SEE IF THE 12Z RUNS OF THE AI/ML MODELS AGREE WITH THIS, BUT THE
00Z RUNS LARGELY DID NOT. BY FRIDAY, THERE IS REMARKABLE AGREEMENT
AMONGST NEARLY ALL GUIDANCE FOR A DEEP SURFACE LOW TO EMERGE IN
THE CENTRAL HIGH PLAINS AHEAD OF THE HIGHLY AMPLIFIED TROUGH AXIS.
FOR THE FIRST HALF OF THE MEDIUM RANGE PERIOD, THE WPC FORECAST
FAVORED A GENERAL MODEL BLEND OF DETERMINISTIC GUIDANCE, FAVORING
THE 00Z ECMWF AND THE 06Z GFS. BEYOND DAY 5, THE BLEND GRADUALLY
LESSENED THE PROPORTION OF THE DETERMINISTIC MODELS IN FAVOR OF
THE EC AND GEFS ENSEMBLE MEANS AS THE PERIOD PROGRESSED.
..WEATHER/HAZARDS HIGHLIGHTS
ON MONDAY, RAIN IS LOOKING INCREASINGLY LIKELY ACROSS THE
SOUTHEAST/CAROLINAS NEAR THE SURFACE LOW TRACK. MODEL SPREAD IN
THE PLACEMENT AND AMOUNTS OF THE QPF HAS BEEN REDUCED WITH THIS
CYCLE, AS MOST GUIDANCE NOW DEPICTS A PERIOD OF STEADIER MODERATE
TO EVEN BORDERLINE HEAVY RAIN THROUGH THE DAY AND POSSIBLY THE
NIGHT. HOWEVER, INSTABILITY WITHIN THE DEFORMATION AXIS ON THE COLD
SIDE OF THE LOW LOOKS TO BE MINIMAL, WHICH SHOULD LIMIT ANY
PROBLEMATIC RAIN RATES. THUS, OPTED TO LEAVE THE CURRENT NULL EXCESSIVE
RAINFALL RISK AS IS. MEANWHILE, SOME LOWER ELEVATION RAIN AND
HIGHER ELEVATION SNOW IS FORECAST TO COME INTO CENTRAL AND SOUTHERN
CALIFORNIA MONDAY AND SPREADING INTO THE SOUTHWEST TUESDAY, BUT
THIS ALSO APPEARS TO BE BELOW ERO THRESHOLDS. THEN THE MAIN
ATMOSPHERIC RIVER WILL COME INTO THE WEST AHEAD OF THE DEEP EASTERN
PACIFIC/WEST TROUGH BY LATE TUESDAY OR WEDNESDAY. THERE IS SOME
MODEL VARIABILITY ON WHEN EXACTLY THE INITIAL PUSH OF THE AR COMES
ASHORE, WITH SOME POTENTIAL FOR THAT TO OCCUR ON TUESDAY NIGHT
BEFORE 12Z WEDNESDAY, SO WITHIN THE DAY 5 ERO PERIOD. DECIDED TO
HOLD OFF FROM DELINEATING A MARGINAL RISK ON THE DAY 5 ERO BECAUSE
SOME MODELS HELD OFF UNTIL WEDNESDAY, BUT WILL HAVE TO KEEP A CLOSE
EYE ON THE TIMING OF THE AR AND WHEN THE MODERATE TO HIGH RAIN
RATES BEGIN. AREAS OF RAIN AND HIGHER ELEVATION SNOW SHOULD SPREAD
ACROSS MUCH OF THE WEST WEDNESDAY-THURSDAY. HIGH WINDS WILL ALSO
BE A CONCERN ACROSS MUCH OF THE WEST. BY NEXT FRIDAY, WILL ALSO
MONITOR THE POSSIBILITY OF SNOW IN THE NORTHERN/CENTRAL PLAINS ON
THE BACKSIDE OF THE SURFACE LOW EMERGING IN THE CENTRAL HIGH
PLAINS.
FARTHER EAST, RAIN IS FORECAST TO SPREAD ACROSS THE TENNESSEE
VALLEY AND SOUTHEAST MIDWEEK AHEAD OF A COUPLE OF FRONTAL SYSTEMS.
LIGHT SNOW IS POSSIBLE ON THE NORTHERN SIDE AROUND THE GREAT LAKES
REGION. THIS PRECIPITATION SHOULD SPREAD ACROSS THE APPALACHIANS TO
EASTERN SEABOARD ON THURSDAY, WITH SOME NORTHERN NEW ENGLAND SNOW
POSSIBLE.
ABOVE AVERAGE TEMPERATURES ARE LIKELY EARLY NEXT WEEK IN THE
NORTH- CENTRAL U.S. UNDERNEATH THE UPPER RIDGE. TEMPERATURES OF
15-30 DEGREES ABOVE AVERAGE COULD PUSH HIGHS WELL INTO THE 60S FROM
THE DAKOTAS INTO IOWA. THE UPPER RIDGE AND THUS THE WARMTH WILL
EXPAND EASTWARD ACROSS THE GREAT LAKES/OHIO VALLEY AND MID-
ATLANTIC/NORTHEAST WITH TEMPERATURES GENERALLY 15-20 DEGREES ABOVE
NORMAL FOR TUESDAY AND WEDNESDAY. HIGHS IN THE 70S ARE LIKELY FROM
THE LOWER OHIO VALLEY TO MID-ATLANTIC. WARMER THAN NORMAL
TEMPERATURES ARE FORECAST TO SPREAD ACROSS THE SOUTHERN TIER AS THE
WEEK PROGRESSES, FOR WARMER THAN NORMAL TEMPERATURES MOST
EVERYWHERE EAST OF THE ROCKIES. TEMPERATURES COULD NEAR 100F IN
SOUTH TEXAS BY NEXT FRIDAY. MEANWHILE THE TROUGHING ACROSS THE WEST
ALONG WITH INCREASING CLOUDS AND PRECIPITATION WILL PROMOTE BELOW
NORMAL TEMPERATURES ESPECIALLY FOR HIGHS, GROWING IN MAGNITUDE AND
AREA AS THE WEEK PROGRESSES.
MILLER/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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