126
FXUS02 KWBC 231859
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EST SUN FEB 23 2025
VALID 12Z WED FEB 26 2025 - 12Z SUN MAR 02 2025
..OVERVIEW
THE UPPER FLOW PATTERN SHOULD REMAIN RATHER PROGRESSIVE THROUGH
MUCH OF THE MEDIUM RANGE PERIOD. AT THE START OF THE PERIOD ON
WEDNESDAY, A SHORTWAVE ATOP THE NORTH-CENTRAL U.S. SHOULD
EVENTUALLY DEEPEN OVER THE EAST THURSDAY INTO FRIDAY, WITH
SECONDARY REINFORCING ENERGY BY SATURDAY. A RIDGE AXIS OVER THE
WEST WILL BE UNDERCUT BY A SOUTHERN STREAM CUTOFF LOW MOVING
INLAND ACROSS SOUTHERN CALIFORNIA AND THE SOUTHWEST THIS WEEKEND.
ANOTHER DEEP AND ELONGATED UPPER TROUGH LOOKS TO MOVE INTO THE WEST
COAST NEXT SUNDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THERE CONTINUES TO BE REASONABLE AGREEMENT ON THE LARGE SCALE
PATTERN DURING THE MEDIUM RANGE PERIOD, BUT STILL PLENTY OF
UNCERTAINTY IN THE DETAILS, SOME OF WHICH COULD HAVE NOTABLE
SENSIBLE WEATHER IMPACTS. INTO THURSDAY, A SHORTWAVE MOVING THROUGH
THE DEEPENING EAST-CENTRAL U.S. TROUGH LEADS TO SOME MINOR MODEL
DIFFERENCES IN THE ASSOCIATED SURFACE LOW POSITION OVER THE GREAT
LAKES OR SO, WITH THE GFS/UKMET FARTHER EAST OF THE CMC/EC. A
POSITION IN BETWEEN APPEARS BEST CONSIDERING THE AI MODELS AS WELL,
AND THE 12Z MODELS HAVE CONVERGED BETTER ON A POSITION. THEN BY
FRIDAY-SUNDAY, THE NEXT SHORTWAVE AND SURFACE LOW WILL TRACK FROM
SOUTH-CENTRAL CANADA THROUGH THE GREAT LAKES REGION AND NORTHEAST.
THE 00Z ECMWF APPEARED TO BE A NORTHERN OUTLIER COMPARED TO THE
DYNAMICAL AND AI GUIDANCE ON FRIDAY AND THEN BECAME SLOW BY SUNDAY.
THE 12Z EC LOOKED MORE REASONABLE BUT THERE IS STILL SOME MODEL
SPREAD TO KEEP AN EYE ON.
FARTHER WEST, MODELS CONTINUE TO WAFFLE ON THE TIMING AND POSITION
OF THE SOUTHERN STREAM UPPER LOW AS IT MOVES INTO SOUTHERN
CALIFORNIA ON FRIDAY. THE 00Z/06Z DETERMINISTIC MODELS WERE
ACTUALLY PRETTY AGREEABLE ON THE TIMING, WITH THE EC AND CMC
ENSEMBLE MEANS IN LINE, BUT THE GEFS MEANS WERE FASTER. BUT THE
NEWER 12Z EC/GFS RUNS JUMPED FARTHER WEST AND MAINTAIN A BIT SLOWER
OF A TRACK INTO THE SOUTHWEST TO SOUTHERN PLAINS THROUGH THE
WEEKEND. SO STILL SOME MODEL VARIATIONS THERE TO MONITOR. TO THE
NORTH THERE IS ALSO MODEL SPREAD WITH THE TROUGH MOVING ACROSS THE
EASTERN PACIFIC TOWARD THE PACIFIC NORTHWEST/CALIFORNIA NEXT
WEEKEND. GFS RUNS ARE PARTICULARLY SLOW AND CLOSE OFF AN UPPER LOW
WELL OFFSHORE NORTHERN CALIFORNIA; THE EC AND OTHER GUIDANCE
INCLUDING BOTH EC-BASED AND GFS-BASED AI MODELS HAVE THE TROUGH
COMING IN FASTER THAN THE GFS AND CMC. THUS LEANED TOWARD THE EC/EC
MEAN FOR THIS FEATURE.
THE WPC FORECAST USED A BLEND OF DETERMINISTIC MODELS FAVORING THE
GFS AND ECMWF EARLY IN THE PERIOD. AS THE PERIOD PROGRESSED,
QUICKLY RAMPED UP THE PROPORTION OF ENSEMBLE MEANS, PARTICULARLY
THE EC MEAN, GIVEN THE INCREASING SPREAD WITH MULTIPLE FEATURES.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT SHIFTING ACROSS THE OHIO/TENNESSEE VALLEYS INTO THE
EASTERN SEABOARD WILL SPREAD GENERALLY LIGHT TO MODERATE
PRECIPITATION ACROSS THIS REGION WEDNESDAY INTO THURSDAY. SOME
PRECIPITATION COULD BE SNOW IN THE NORTHERN PART OF THE
PRECIPITATION SHIELD ACROSS THE INTERIOR NORTHEAST. A CLIPPER
SYSTEM SHOULD BRING AN ADDITIONAL ROUND OF PRECIPITATION TO THE
GREAT LAKES AND NORTHEAST FRIDAY INTO SATURDAY.
A BUILDING RIDGE SHOULD KEEP CONDITIONS QUIET AND DRY ACROSS THE
WEST WEDNESDAY AND THURSDAY, OTHER THAN A LITTLE LIGHT
PRECIPITATION POSSIBLE IN THE PACIFIC NORTHWEST. THE SOUTHERN
STREAM UPPER LOW MOVING ACROSS SOUTHERN CALIFORNIA FRIDAY AND
INLAND NEXT WEEKEND MAY LEAD TO LIGHT SHOWERS OVER CALIFORNIA, THE
SOUTHWEST, AND INTO THE SOUTH-CENTRAL U.S., WITH INCREASING RAIN
CHANCES IN THE SOUTHERN PLAINS BY NEXT SUNDAY AS MOISTURE
INCREASES. THE NORTHERN STREAM TROUGH MOVING THROUGH THE EASTERN
PACIFIC AND INTO THE WEST NEXT WEEKEND WILL ALSO BRING
PRECIPITATION BACK INTO THE FORECAST FOR THE WEST COAST AND GREAT
BASIN.
BY THE START OF THE PERIOD ON WEDNESDAY, MUCH OF THE LOWER 48 WILL
BE MUCH ABOVE NORMAL IN TERMS OF TEMPERATURES, WITH DECENT
COVERAGE OF PLUS 10-20 DEGREE ANOMALIES. THE NORTHERN/CENTRAL
PLAINS CAN EXPECT THE HIGHEST ANOMALIES OF 20 TO LOCALLY 30 DEGREES
ABOVE NORMAL, WITH 60S FOR HIGHS AS FAR NORTH AS NEBRASKA OR
PERHAPS EVEN SOUTH DAKOTA AT TIMES. THE SOUTHWEST AND GREAT BASIN
CAN ALSO EXPECT WARMER THAN AVERAGE CONDITIONS UNDERNEATH THE
BUILDING UPPER RIDGE. PARTS OF THE DESERT SOUTHWEST COULD REACH
INTO THE 90S ESPECIALLY WEDNESDAY, AND SOME SITES COULD SET DAILY
RECORD HIGH MAX/MIN TEMPERATURES IN THE VICINITY. AREAS EAST OF THE
MISSISSIPPI SHOULD ALSO SEE WARM CONDITIONS INTO WEDNESDAY, BUT
ARE LIKELY TO COOL BACK TO NEAR NORMAL (OR SLIGHTLY BELOW IN SPOTS)
BY LATE WEEK UNDERNEATH UPPER TROUGHING.
TATE/SANTORELLI
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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