611
FXUS02 KWBC 100702
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 AM EDT MON MAR 10 2025
VALID 12Z THU MAR 13 2025 - 12Z MON MAR 17 2025
...POTENT SYSTEM BRINGS PRECIPITATION TO THE WEST INTO THURSDAY,
THE CENTRAL U.S. FRIDAY, AND TOWARD THE EAST-CENTRAL/EASTERN U.S.
NEXT WEEKEND...
..OVERVIEW
THE PRIMARY WEATHER FEATURE OF CONCERN LATER THIS WEEK WILL BE A
DEEP AND PHASED UPPER TROUGH NEAR THE WEST COAST BY EARLY THURSDAY
THAT CLOSES OFF AN EMBEDDED UPPER LOW OVER THE PLAINS ON FRIDAY
WHILE SPINNING UP A STRONG SURFACE LOW. THE UPPER TROUGH WILL BRING
WIDESPREAD RAIN AND HIGHER ELEVATION SNOW ACROSS THE WEST ON
THURSDAY. THEN HAZARDS ASSOCIATED WITH THE SURFACE LOW PRESSURE
SYSTEM WILL INCLUDE HEAVY RAIN AND SEVERE THUNDERSTORMS IN THE
MISSISSIPPI VALLEY BEGINNING FRIDAY AND INTO THE SOUTHEAST AND
TENNESSEE/LOWER OHIO VALLEYS SATURDAY. CONVECTION SHOULD REACH THE
EASTERN SEABOARD SUNDAY. SNOW IS POSSIBLE ON THE BACKSIDE OF THE
LOW IN THE NORTHERN HALF OF THE PLAINS INTO THE UPPER MIDWEST
FRIDAY-SATURDAY. MEANWHILE AREAS OF STRONG WINDS ARE LIKELY, WHICH
COULD CAUSE FIRE DANGER ESPECIALLY IN THE SOUTHERN PLAINS. BEHIND
THAT SYSTEM, ANOTHER UPPER TROUGH IS FORECAST TO APPROACH THE WEST
THIS WEEKEND AND SPREAD ADDITIONAL PRECIPITATION THERE. THE LEADING
PACIFIC TROUGH CROSSING THE WEST WILL BRING BELOW NORMAL HIGHS TO
THAT REGION WHILE THE LEADING RIDGE (AND POSSIBLY A WEAKER ONE
FARTHER EAST) SHOULD PROMOTE ABOVE NORMAL TEMPERATURES OVER THE
CENTRAL/EASTERN U.S., GRADUALLY LESSENING IN SCOPE WITH TIME.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD/BETTER THAN AVERAGE AGREEMENT WITH
THE SYNOPTIC PATTERN THROUGH THE WEEKEND, AS THE UPPER TROUGH MOVES
THROUGH THE WEST THURSDAY AND CONSOLIDATES ENERGY TO DEVELOP A LOW
ALOFT THAT SUPPORTS A QUICKLY STRENGTHENING SURFACE LOW THAT
TRACKS ACROSS THE CENTRAL PLAINS TO UPPER MIDWEST. THE EXACT DEPTH
OF THE LOW IS STILL IN QUESTION, WITH OPERATIONAL GUIDANCE
GENERALLY DEEPER THAN AI/ML MODELS IN THE 970S. THE WPC FORECAST
BLEND WAS BASED ON DETERMINISTIC MODELS FAVORING THE 12Z EC AND 18Z
GFS DURING THE FIRST HALF OF THE MEDIUM RANGE PERIOD.
INTO EARLY NEXT WEEK, MOST GUIDANCE SHOWS A LOW AMPLITUDE RIDGE
BEHIND THE MAIN UPPER TROUGH, WITH ADDITIONAL TROUGHING FORMING
UPSTREAM IN THE EASTERN PACIFIC TOWARD THE WEST COAST. THE TROUGH
WILL SUPPORT A SURFACE LOW THAT CONTINUES TO VARY QUITE A BIT WITH
ITS DEPTH CONSIDERING DIFFERENCES IN SUPPORTING SHORTWAVE ENERGY
WITHIN THE MORE PREDICTABLE MEDIUM TO LARGER SCALE UPPER TROUGH.
THE 12Z CMC WAS AMONG THE STRONGEST WITH THE SURFACE LOW IN THE
970S 12Z SUNDAY BUT THE 00Z GFS CAME IN ALMOST AS STRONG. THE
MANUAL FORECAST STAYS ON THE CONSERVATIVE SIDE DEPTH-WISE GIVEN THE
WIDE SPREAD AMONG DYNAMICAL AND ML GUIDANCE AT THIS TIME. THE
ORIENTATION AND TIMING OF THE TROUGH ALSO HAVE SOME MODEL SPREAD.
IN PARTICULAR, THE 12Z CONTROL RUN OF THE ECMWF WAS SLOWER/FARTHER
SOUTHWEST WITH THE TROUGH AXIS COMPARED TO THE BULK OF OTHER
GUIDANCE, INCLUDING THE EC-BASED AI/ML MODELS, SO LEANED AWAY FROM
THAT. THE 00Z EC HAS ADJUSTED FAVORABLY SOMEWHAT EASTWARD. INTO THE
LATER PERIOD, THE FORECAST BLEND INCLUDED AND GRADUALLY INCREASED
THE PROPORTION OF GEFS AND EC ENSEMBLE MEANS TO ABOUT HALF DAY 6
AND MORE DAY 7 WITH THE INCREASING SPREAD.
..WEATHER/HAZARDS HIGHLIGHTS
ON THURSDAY, THE TAIL END OF A WEAK ATMOSPHERIC RIVER AND POSSIBLE
CONVECTIVE SHOWERS BEHIND IT COULD BRING MODERATE TO HEAVY
PRECIPITATION TO SOUTHERN CALIFORNIA, AND A MARGINAL RISK REMAINS
IN PLACE IN THE DAY 4 ERO. MORE BROADLY, AREAS OF RAIN AND HIGHER
ELEVATION SNOW ARE FORECAST ACROSS MUCH OF THE WEST INTO THURSDAY.
HIGHER ELEVATION SNOW COULD BE HEAVY ACROSS THE SIERRA NEVADA AND
INTO THE TERRAIN OF THE CENTRAL GREAT BASIN AND MOGOLLON RIM.
WIDESPREAD HIGH WINDS WILL ALSO BE A CONCERN IN THE WEST ON
THURSDAY.
AHEAD OF THIS SYSTEM, AN INITIAL SHORTWAVE WILL PRODUCE SOME LIGHT
TO MODERATE RAIN ACROSS THE SOUTHEAST ON THURSDAY. PRECIPITATION
REMAINS MORE QUESTIONABLE FARTHER NORTH, BUT WITH A GENERAL FOCUS
FOR LIGHT PRECIPITATION FROM THE GREAT LAKES/OHIO VALLEY REGION TO
THE NORTHEAST.
AS THE PRIMARY UPPER TROUGH MOVES INTO THE CENTRAL U.S., THERE IS
HIGH CONFIDENCE IN SURFACE LOW DEVELOPMENT/CONSOLIDATION IN THE
CENTRAL PLAINS BY FRIDAY WITH STRONG FRONTS. ON THE BACKSIDE OF THE
LOW, SNOW COULD SPREAD ACROSS THE CENTRAL HIGH PLAINS AND INTO THE
DAKOTAS ON FRIDAY AND INTO THE UPPER MIDWEST ON SATURDAY. SOME OF
THESE AREAS MAY INITIALLY SEE RAIN IN THE WARM SECTOR, AND A
TRANSITION ZONE OF ICE IS ALSO POSSIBLE. RAIN AND THUNDERSTORM
CHANCES EMERGE AHEAD OF THE COLD FRONT ACROSS THE MISSISSIPPI
VALLEY FRIDAY. THE STORM PREDICTION CENTER IS HIGHLIGHTING THE BEST
SEVERE POTENTIAL FROM PARTS OF THE MIDWEST SOUTHWARD ALMOST TO THE
WEST-CENTRAL GULF COAST ON FRIDAY. MOST GUIDANCE SHOWS HEAVY RAIN
RATES BEGINNING LATE FRIDAY INTO FRIDAY NIGHT THAT COULD CAUSE
FLOODING CONCERNS. THE FIRST TAKE AT THE DAY 5 ERO FOR FRIDAY
INDICATES A MARGINAL RISK FOR THE LOWER/MIDDLE MISSISSIPPI VALLEY
AND MID-SOUTH. RAIN TOTALS ARE FORECAST TO BECOME EVEN HEAVIER BY
SATURDAY CENTERED IN THE TENNESSEE VALLEY, AND SPC INDICATES SEVERE
POTENTIAL FOR THE TENNESSEE VALLEY AND SOUTHEAST. AS THE UPPER
TROUGH AND SURFACE FRONTS MOVE EAST, RAIN AND THUNDERSTORMS WILL
OVERSPREAD THE EAST ON SUNDAY. WINDS ARE ANOTHER POSSIBLE CONCERN
NEAR THE DEEP LOW TRACK, AS WELL AS IN THE PLAINS BEHIND THE COLD
FRONT. CURRENTLY THE GUIDANCE SHOWS THE POTENTIAL FOR HIGHEST WIND
SPEEDS OVER THE SOUTHERN ROCKIES/HIGH PLAINS AROUND FRIDAY, LIKELY
PRODUCING FIRE WEATHER CONCERNS. IN ADDITION SOUTHERLY WINDS IN THE
WARM SECTOR COULD GET FAIRLY STRONG OVER/NEAR THE APPALACHIANS AND
EAST COAST NEXT WEEKEND.
ADDITIONAL ROUNDS OF PRECIPITATION ARE LIKELY IN THE WEST LATE
THIS WEEK INTO THE WEEKEND AS ANOTHER FRONTAL SYSTEM OR TWO
APPROACH. RAIN AMOUNTS IN THE PACIFIC NORTHWEST TO NORTHERN
CALIFORNIA LOOK TO STAY BELOW THRESHOLDS FOR ANY EXCESSIVE RAINFALL
RISK THROUGH FRIDAY, BUT CHANCES FOR HEAVY PRECIPITATION (LOWER
ELEVATION RAIN AND HIGHER ELEVATION SNOW) COULD INCREASE BY THE
WEEKEND FOR THE PACIFIC NORTHWEST INTO CALIFORNIA.
ABOVE AVERAGE TEMPERATURES ARE LIKELY OVER MOST AREAS EAST OF THE
ROCKIES TO START THE PERIOD. TEMPERATURE ANOMALIES OF 20 TO AS MUCH
AS 35 DEGREES ABOVE NORMAL ARE FORECAST THURSDAY FOR THE NORTHERN
PLAINS TO MIDWEST AS HIGHS REACH THE 60S AND 70S. FARTHER SOUTH,
TEMPERATURES IN TEXAS AND LOUISIANA COULD REACH THE 80S WHILE
LOCALIZED AREAS LIKE FAR SOUTH TEXAS CAN EXPECT 90S, EVEN
APPROACHING 100F. WARMER THAN NORMAL TEMPERATURES WILL GRADUALLY
SHRINK IN AREA LATE WEEK INTO THE WEEKEND AS POSSIBLY MULTIPLE COLD
FRONTS TRACK EAST. THE MIDWEST AND GREAT LAKES CAN EXPECT PLUS
20-30F ANOMALIES ON FRIDAY BUT MORE LIMITED TO THE GREAT LAKES ON
SATURDAY, AND WARMER THAN NORMAL TEMPERATURES BY 10-20F ARE LIKELY
IN THE NORTHEAST OVER THE WEEKEND. DAILY RECORD HIGHS LOOK FAIRLY
ISOLATED ACROSS THE CENTRAL TO EASTERN U.S., BUT THERE COULD BE
MORE WIDESPREAD RECORD WARM LOWS FROM THE MIDWEST THROUGH THE EAST
FRIDAY-SUNDAY IF THE MORNING MINS HOLD FOR THE CALENDAR DAY. IN THE
WEST, THE UPPER TROUGHING ALONG WITH CLOUDS AND PRECIPITATION WILL
PROMOTE BELOW NORMAL TEMPERATURES SPREADING ACROSS THE REGION MID-
LATE WEEK. HIGHS ARE FORECAST TO BE GENERALLY BELOW AVERAGE BY
15-20 DEGREES FOR THE CENTRAL GREAT BASIN AND SOUTHWEST, WHILE LOWS
OF 5-15 DEGREES BELOW NORMAL ARE LIKELY. TEMPERATURES SHOULD
MODERATE SOMEWHAT OVER THE WEEKEND AS THE TROUGH PULLS AWAY, BUT
ANOTHER TROUGH APPROACHING COULD LEAD TO ANOTHER BOUT OF COOL
TEMPERATURES THERE EARLY NEXT WEEK.
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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