711
FXUS02 KWBC 070717
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
217 AM 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 COULD PRODUCE SOME RAIN INTO 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. 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
THERE IS SOME MODEL SPREAD EVEN EARLY IN THE MEDIUM RANGE PERIOD
NEXT WEEK WITH THE DETAILS OF SOME FEATURES THAT COULD CAUSE
SENSIBLE WEATHER IMPACTS. THE FIRST OF NOTE WAS THE SHORTWAVE/SMALL
UPPER LOW AND SURFACE LOW MOVING THROUGH THE SOUTHEAST.
FORTUNATELY THE 18Z AND NOW THE NEWER 00Z GFS HAVE SLOWED DOWN AND
ARE IN BETTER ALIGNMENT WITH THE NON-NCEP GUIDANCE COMPARED TO
OLDER GFS RUNS THAT WERE QUITE FAST. HOWEVER THERE ARE STILL SOME
DIFFERENCES IN THE ORIENTATION OF THE UPPER LOW OPENING UP, E.G. A
POSITIVELY TILTED SHORTWAVE WOULD KEEP QPF SUPPRESSED SOUTHEASTWARD
INTO GA/SC AND OFFSHORE. BUT MANY OF THE GFS- AND EC-BASED AI/ML
MODELS INDICATED QPF FARTHER NORTH IN THE CAROLINAS. SECOND, IN THE
WEST EARLY NEXT WEEK, THE EC AND GFS SUITES SHOWED GOOD AGREEMENT
IN THE TIMING OF THE UPPER LOW MOVING IN--BUT THE 12Z CMC AND
ESPECIALLY THE UKMET WERE FASTER. THE 00Z CMC AND UKMET BOTH SLOWED
AND MORE FAVORABLY MATCHED THE EC/GFS CONSENSUS. SHALLOW
SHORTWAVES IN THE NORTHERN STREAM ALSO SHOWED SOME MODEL SPREAD
THAT NECESSITATED TYPICAL CHANGES TO THE ASSOCIATED FRONTAL AND
SURFACE LOW TIMING; THE SURFACE LOW NORTH OF THE GREAT LAKES
TUESDAY TRENDED DEEPER COMPARED TO THE PREVIOUS FORECAST.
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. MEANWHILE MODEL AGREEMENT IS GOOD
FOR TROUGHING TO MAKE ITS WAY FROM THE EASTERN PACIFIC WEDNESDAY
INTO THE WEST COAST THURSDAY. THE NEW 00Z ECMWF IS RATHER
AGGRESSIVE IN SHOWING A CLOSED LOW WITHIN THE UPPER TROUGH BY
WEDNESDAY OFFSHORE OF THE PACIFIC NORTHWEST AND DEEP WITH THE
ASSOCIATED SURFACE LOW. WILL HAVE TO SEE IF THE 00Z RUNS OF THE
AI/ML MODELS AGREE WITH THIS. A LITTLE MORE SPREAD ARISES BY FRIDAY
AS THE 12Z CMC BRINGS A SHORTWAVE IN THE EASTERN PACIFIC UPSTREAM
AND DISRUPTS THE TROUGH A BIT, WHILE THE 18Z GFS MAY BE A BIT WEST
WITH THE TROUGH AXIS. A DEEP SURFACE LOW LOOKS TO EMERGE IN THE
CENTRAL HIGH PLAINS BY NEXT FRIDAY AHEAD OF THE TROUGH AXIS.
FOR THE EARLY PART OF THE MEDIUM RANGE PERIOD, THE WPC FORECAST
FAVORED THE 12Z ECMWF WITH LESSER PROPORTIONS OF THE 18Z GFS, 12Z
CMC, AND THE 12Z EC ENSEMBLE MEAN. GRADUALLY LESSENED THE
PROPORTION OF THE DETERMINISTIC MODELS AND ELIMINATED THE CMC IN
FAVOR OF THE ENSEMBLE MEANS AS THE PERIOD PROGRESSED. THE MEANS
REACHED HALF THE BLEND BY DAY 7 THOUGH WITH A HEALTHY PROPORTION OF
THE 12Z ECMWF.
..WEATHER/HAZARDS HIGHLIGHTS
ON MONDAY, RAIN IS POSSIBLE ACROSS THE SOUTHEAST/CAROLINAS NEAR
THE SURFACE LOW TRACK. THERE IS SOME MODEL SPREAD IN THE PLACEMENT
AND AMOUNTS OF THE QPF, PLUS INSTABILITY LOOKS TO BE ON THE LOW
SIDE LIMITING RAIN RATES, TO PRECLUDE ANY EXCESSIVE RAINFALL RISK
AT THIS POINT. 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. HOWEVER, ON TUESDAY
NIGHT, THE MAIN ATMOSPHERIC RIVER MAY PUSH ASHORE IN SOUTHERN
OREGON AND NORTHERN CALIFORNIA AHEAD OF THE DEEP EASTERN
PACIFIC/WEST TROUGH. WHILE WEDNESDAY SHOULD BE THE WETTER DAY
OVERALL, THE INITIAL PUSH OF THE AR INLAND WITH ASSOCIATED MODERATE
TO HIGH RAIN RATES LOOKS LIKE IT MAY OCCUR BEFORE 12Z WEDNESDAY,
THUS DURING THE DAY 5 ERO PERIOD. HAVE A MARGINAL RISK DRAWN UP IN
THE DAY 5 ERO TO COVER TUESDAY NIGHT, BUT WILL HAVE TO KEEP A CLOSE
EYE ON THE TIMING OF THE AR. 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.
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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