381
FXUS02 KWBC 101900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM 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
MOST DYNAMICAL GUIDANCE AGREES REASONABLY WELL FOR THE LARGE SCALE
PATTERN EVOLUTION, WITH MODEST SPREAD FOR THE DEEP PLAINS/UPPER
MIDWEST STORM AND ASSOCIATED UPPER TROUGH ALONG WITH ACCEPTABLE
CLUSTERING FOR THE NEXT UPPER TROUGH NEARING THE WEST COAST BY NEXT
MONDAY. SOME GUIDANCE GUIDANCE DIFFERS MORE SIGNIFICANTLY FOR
SMALLER SCALE FRONTAL WAVE DETAILS OVER THE EASTERN HALF OF THE
COUNTRY DURING THE WEEKEND AS WELL AS FOR SPECIFICS OF THE SURFACE
SYSTEM NEARING THE WEST COAST AROUND SUNDAY AHEAD OF THE SECOND
UPPER TROUGH. THE EARLY-MID PART OF THE FORECAST MAINTAINED GOOD
CONTINUITY BY WAY OF A 06Z/00Z MODEL COMPOSITE WITH MORE GFS/ECMWF
EMPHASIS RELATIVE TO THE UKMET/CMC. DAYS 6-7 SUNDAY-MONDAY
INTRODUCED 20-40 PERCENT TOTAL WEIGHT OF THE 06Z GEFS/00Z ECENS
MEANS, LEADING TO MODEST DETAIL ADJUSTMENTS WITHIN THE MORE
PERSISTENT GENERAL EVOLUTION OF FORECAST SYSTEMS.
FOR THE CENTRAL HIGH PLAINS THROUGH UPPER MIDWEST STORM FRIDAY-
SATURDAY, GUIDANCE AS A WHOLE HAS BEEN FAIRLY STEADY OVER THE PAST
DAY WITH SOME LINGERING TYPICAL SPREAD FOR DEPTH/TRACK/TIMING. AS
OF EARLY FRIDAY OVER THE HIGH PLAINS, THE MEMBERS FROM MOST
ENSEMBLE SYSTEMS FAVOR A DEPTH IN THE 980S MB (SOME GEFS MEMBERS
LEANING A BIT DEEPER). THEN BY SATURDAY ENSEMBLE MEMBERS
CONCENTRATE IN THE 970S MB. OPERATIONAL MODELS GENERALLY FIT WITHIN
THIS ENVELOPE. AHEAD OF THIS SYSTEM BY EARLY SATURDAY, THERE IS
SOME DIVERGENCE IN GUIDANCE FOR HOW QUICKLY THE FRONT NEAR THE EAST
COAST MAY RETURN NORTH AS A WARM FRONT. IN PARTICULAR THERE ARE
SOME MACHINE LEARNING (ML) MODELS THAT SUGGEST POTENTIAL FOR
SURFACE RIDGING TO BE MORE PERSISTENT NORTH OF THE FRONT THAN SEEN
IN THE DYNAMICAL GUIDANCE, DELAYING NORTHWARD PROGRESS.
THEN BY SATURDAY INTO SUNDAY LATEST GUIDANCE IS SHOWING MORE OF A
SIGNAL TODAY THAT THE FRONT ANCHORED BY THE CENTRAL U.S. STORM MAY
CONTAIN A WESTERN GULF COAST INTO GREAT LAKES WAVE. THUS FAR THE
DYNAMICAL MODELS SAY THAT THE PARENT LOW WILL CONTINUE NORTHEAST
INTO CANADA WITH THE FRONTAL WAVE LAGGING, BUT A NUMBER OF RECENT
ML MODELS HAVE BEEN SHOWING SLOW ENOUGH PROGRESSION OF THE MAIN LOW
FOR THE FRONTAL WAVE TO MERGE WITH IT OVER THE GREAT LAKES BY
EARLY SUNDAY. WILL MONITOR FOR ANY DYNAMICAL MODEL TRENDS, BUT FOR
NOW THE FORECAST DOES NOT ACCOUNT FOR THE ALTERNATIVE ML MODEL
SCENARIO. HEADING INTO NEXT MONDAY THERE IS ALSO SPREAD FOR FRONTAL
TIMING AND POSSIBLE ADDITIONAL EMBEDDED WAVINESS DUE TO
DIFFERENCES IN HOW ENERGY IS DISTRIBUTED WITHIN THE OVERALL UPPER
TROUGH. THIS LEADS TO SIGNIFICANT DIFFERENCES FOR
EXISTENCE/MAGNITUDE OF RAINFALL ALONG THE EAST COAST. POSSIBLY DUE
IN PART TO THAT ALTERNATIVE ML EVOLUTION, ML FRONTAL TIMING LEANS
SLOWER THAN THE DYNAMICAL CONSENSUS BY MONDAY, THOUGH THE 00Z/06Z
AVERAGE HAS NUDGED A BIT SLOWER VERSUS CONTINUITY. THE 12Z ECMWF
HAS TRENDED SLOWER AS WELL.
FOR THE SYSTEM THAT MAY APPROACH THE PACIFIC NORTHWEST/VANCOUVER
ISLAND BY NEXT SUNDAY, THERE WAS STILL A LOT OF SPREAD FOR SYSTEM
SPECIFICS THROUGH THE 00Z/06Z CYCLE GIVEN DEPENDENCE ON SMALL-SCALE
EVOLUTION OF SUPPORTING DYNAMICS. THIS SPREAD INCLUDES A BROAD
ENVELOPE FOR TRACK AND DEPTH AMONG ENSEMBLE MEMBERS AND SEPARATE
CLUSTERS DEPICTED BY THE ML MODELS. HOWEVER THERE WAS VERY LITTLE
SUPPORT FOR THE SUPPRESSED STRUCTURE IN THE PAST COUPLE ECMWF RUNS.
THUS PREFERENCE FAVORED THE DEPICTION NON- ECMWF MODELS AND THE
ENSEMBLE MEANS, STILL LEANING ON THE WEAKER SIDE DUE TO DEPTH
UNCERTAINTY (THOUGH A FEW MB DEEPER THAN CONTINUITY). INCOMING 12Z
GUIDANCE SUGGESTS GROWING CONFIDENCE IN A STRONGER SYSTEM, WITH THE
NEW ECMWF NOW LOOKING MORE SIMILAR IN SHAPE TO OTHER DYNAMICAL
MODELS. AN AVERAGE OF GUIDANCE LOOKS GOOD FOR RESOLVING
TIMING/DETAIL DIFFERENCES WITH THE UPPER TROUGH AND ASSOCIATED
SURFACE REFLECTION OVER THE WEST BY NEXT MONDAY.
..WEATHER/HAZARDS HIGHLIGHTS
ON THURSDAY, THE TAIL END OF A WEAK ATMOSPHERIC RIVER (WITH
PRECIPITABLE WATER VALUES BRIEFLY AROUND 2-3 STANDARD DEVIATIONS
ABOVE NORMAL VERY EARLY IN THE DAY) 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
WITH LATEST GUIDANCE MAINTAINING SUPPORT. 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, WITH LATEST GUIDANCE
BECOMING LIGHTER AND MORE SCATTERED WITH ANY GREAT LAKES/OHIO
VALLEY INTO NORTHEAST ACTIVITY THAT DOES OCCUR.
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 AND NORTHEASTWARD
PROGRESSION OF THE SYSTEM THEREAFTER. POTENTIAL EXISTS FOR THIS LOW
TO CHALLENGE SOME SEA LEVEL PRESSURE RECORDS FOR MARCH FROM
EASTERN NEBRASKA INTO PARTS OF MINNESOTA/WISCONSIN. 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. BEST POTENTIAL OF
MEANINGFUL SNOW WAITS UNTIL SATURDAY, WHEN PROBABILITIES FOR 0.25
INCH LIQUID IN THE FORM OF SNOW MAXIMIZE IN THE 30 TO SLIGHTLY MORE
THAN 50 PERCENT RANGE OVER WESTERN MINNESOTA AND EASTERN DAKOTAS.
RAIN AND THUNDERSTORM CHANCES WILL EMERGE AHEAD OF THE COLD FRONT
ACROSS THE MISSISSIPPI VALLEY ON 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 (MINUS THE GFS/GEFS) SHOWS HEAVY RAIN RATES BEGINNING
LATE FRIDAY INTO FRIDAY NIGHT THAT COULD CAUSE FLOODING CONCERNS.
THE UPDATED DAY 5 ERO FOR FRIDAY MAINTAINS A MARGINAL RISK FOR THE
LOWER/MIDDLE MISSISSIPPI VALLEY AND MID- SOUTH WITH MINIMAL
ADJUSTMENT FROM CONTINUITY. 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.
DURING FRIDAY-SATURDAY SPC SHOWS A RELATIVELY GREATER SEVERE THREAT
FROM PARTS OF MISSOURI/ARKANSAS INTO MISSISSIPPI AND ALABAMA. 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, WITH ONE FRONTAL SYSTEM FORECAST TO
ARRIVE AROUND FRIDAY-SATURDAY AND ANOTHER STORM/FRONTAL SYSTEM
LIKELY ARRIVING BY SUNDAY. 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. THE UPPER TROUGH SUPPORTING THE LATTER SYSTEM SHOULD
REACH AT LEAST AS FAR EAST AS THE WEST COAST BY MONDAY, LEADING TO
A DECREASE IN PRECIPITATION INTENSITY NEAR THE COAST AND EASTWARD
EXPANSION OF THE MOISTURE SHIELD OVER PARTS OF THE INTERIOR WEST
AND ROCKIES.
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.
RAUSCH/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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