170
FXUS02 KWBC 271912
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
212 PM EST MON JAN 27 2025
VALID 12Z THU JAN 30 2025 - 12Z MON FEB 03 2025
...HEAVY RAIN AND STRONG THUNDERSTORMS EXPECTED ACROSS THE LOWER
MISSISSIPPI VALLEY TO MID-SOUTH TO CLOSE OUT THE WORKWEEK...
..OVERVIEW
THE FORECAST PERIOD BEGINS THURSDAY WITH A CUTOFF UPPER LOW
EJECTING EASTWARD FROM THE SOUTHERN ROCKIES TO THE WESTERN HIGH
PLAINS, AND THIS WILL SUSTAIN A SURFACE LOW THAT IS EXPECTED TO
TRACK FROM TEXAS AND EVENTUALLY TO THE EAST COAST BY SATURDAY. THIS
IS EXPECTED TO FUEL THE DEVELOPMENT OF RAIN AND SOME STRONG/SEVERE
THUNDERSTORMS ACROSS PARTS OF TEXAS THROUGH THE LOWER MISSISSIPPI
VALLEY THURSDAY, MIGRATING EAST TO THE LOWER OHIO/TENNESSEE VALLEYS
AND SOUTHEAST FRIDAY. A COUPLE ROUNDS OF SNOW ARE POSSIBLE ACROSS
THE NORTHERN TIER THROUGH THE PERIOD. BACK ACROSS THE PACIFIC
NORTHWEST, A COLD FRONT AND ASSOCIATED MOISTURE FEED AHEAD OF IT
WILL LEAD TO THE RETURN OF RAIN AND MOUNTAIN SNOW BY FRIDAY AND
CONTINUING INTO THE WEEKEND. MOST OF THE LOWER 48 WILL SEE NEAR OR
ABOVE NORMAL TEMPERATURES THROUGH THE PERIOD, UNTIL EARLY NEXT WEEK
WHEN AN ARCTIC AIRMASS SETTLES ACROSS THE NORTHERN PLAINS BEHIND A
STRONG COLD FRONT.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THE LARGE SCALE
THROUGH LATE WEEK. MODELS CONTINUE TO SHOW A FASTER TREND COMPARED
TO A DAY OR TWO AGO WITH THE EJECTION OF THE UPPER LOW EASTWARD.
BUT THERE ARE STILL SOME VARIATIONS IN JUST HOW FAST IT WILL MOVE
OUT. THROUGH 00/06Z, THE DETERMINISTIC GFS/ECMWF/UKMET WERE FASTER
LATE FRIDAY INTO SATURDAY WITH THE REMAINING SHORTWAVE COMPARED TO
THE CMC AND ENSEMBLE MEANS. THE 12Z CMC HAS JUMPED FASTER. AS THAT
FEATURE WEAKENS, THE PATTERN TRANSITIONS TO MORE ZONAL FLOW OVER
THE WEEKEND WITH SOME SHORTWAVES AND SURFACE LOW VARIATIONS THAT
HAVE TYPICAL PREDICTABILITY ISSUES FOR SMALL SCALE FEATURES. THE
SOMEWHAT MORE NOTABLE MODEL DISCREPANCIES ARE WITH AN UPPER
LOW/TROUGH FOCUSED OFF OF BRITISH COLUMBIA BY EARLY NEXT WEEK. GFS
RUNS SHOW IT ORIENTED SOUTHWEST TO NORTHEAST AND A BIT FARTHER
SOUTH IN THE NORTHWEST COMPARED TO THE ECMWF/CMC, AND THIS HAS
IMPLICATIONS FOR THE POSITION AND MAGNITUDE OF ATMOSPHERIC RIVER
PRECIPITATION. THE 12Z GFS ADJUSTED JUST A BIT IN THE DIRECTION OF
THE NON-NCEP MODELS.
THE WPC FORECAST TRANSITIONED FROM A MULTI-MODEL DETERMINISTIC
BLEND EARLY IN THE FORECAST PERIOD TO AROUND HALF ENSEMBLE MEANS BY
DAYS 6-7 (WITH THE EC THE MAIN REMAINING DETERMINISTIC MODEL) AS
MODEL SPREAD INCREASED.
..WEATHER/HAZARDS HIGHLIGHTS
AN OCCLUDED LOW PRESSURE SYSTEM IS FORECAST TO MOVE ACROSS THE
SOUTHERN PLAINS THURSDAY AND INTO THE MID-MISSISSIPPI VALLEY BY
EARLY FRIDAY. IN THE WARM SECTOR OF THE SURFACE LOW, WARM AIR
ADVECTION IN COMBINATION WITH STRONG FORCING ALOFT WILL CREATE A
FAVORABLE ENVIRONMENT FOR HEAVY RAINFALL FROM THE ARKLATEX REGION
TO THE MID-SOUTH. THERE WILL LIKELY BE A CORRIDOR OF 2 TO 4 INCH
RAINFALL TOTALS ACROSS PORTIONS OF THIS REGION, AND THERE COULD BE
THE POTENTIAL FOR TRAINING/REPEATED CONVECTION AHEAD OF THE
INITIALLY SLOW TRAILING COLD FRONT. A SLIGHT RISK REMAINS IN PLACE
FROM NORTHEAST TEXAS TO NEAR THE GREATER MEMPHIS AREA IN THE DAY
4/THURSDAY ERO. THE LOW PRESSURE SYSTEM IS FORECAST TO MOVE QUICKLY
EASTWARD ON FRIDAY, BUT SOME CONVECTION WITH LOCALLY HEAVY
RAINFALL RATES ALONG THE TRAILING FRONT COULD PRODUCE ISOLATED
FLOODING FROM THE SOUTHEAST TOWARD THE TENNESSEE/OHIO VALLEYS FOR A
LOW-END MARGINAL RISK ON THE DAY 5 ERO.
MEANWHILE WITH THIS SYSTEM, PRECIPITATION CHANCES WILL EXPAND TO
THE WEST AND NORTH OF THE OCCLUDED LOW WITH POTENTIAL FOR SNOW AND
ICE. WINTRY WEATHER IS ANTICIPATED TO LINGER IN THE SOUTH-CENTRAL
ROCKIES TO PLAINS THURSDAY AND COULD SPREAD INTO THE LOWER GREAT
LAKES REGION TO NORTHEAST FRIDAY. CURRENT FORECASTS SHOW POTENTIAL
FOR WINTER WEATHER TO LINGER IN THE NORTHERN MID-ATLANTIC TO
NORTHEAST SATURDAY, WITH WINTER PRECIPITATION PERHAPS REACHING NYC
TO BOSTON. ANOTHER ROUND OF WINTER WEATHER COULD TRACK ACROSS THE
GREAT LAKES TO NORTHEAST ON SUNDAY WITH A CLIPPER SYSTEM.
MOIST INFLOW IS FORECAST TO RETURN TO THE WEST COAST LATE THIS
WEEK, EXPANDING INTO THE NORTHERN GREAT BASIN/ROCKIES, WITH ROUNDS
OF LOW PRESSURE/FRONTAL SYSTEMS TRACKING THROUGH. MAINTAINED A LOW-
END MARGINAL RISK FOR COASTAL NORTHWEST CALIFORNIA THROUGH THE
PACIFIC NORTHWEST FOR DAY 5/FRIDAY AS A MODERATE ATMOSPHERIC RIVER
EVENT BEGINS AND COULD LEAD TO SOME PERIODS OF HEAVIER RAINFALL ON
FRIDAY. THIS IS EXPECTED TO CONTINUE INTO THE WEEKEND AS WELL WITH
ADDITIONAL MOIST ONSHORE FLOW.
TEMPERATURES ARE EXPECTED TO BE ABOVE AVERAGE TO CLOSE OUT THE
WEEK FOR THIS TIME OF YEAR ACROSS MUCH OF THE CENTRAL AND EASTERN
U.S., WITH HIGHS RUNNING ABOUT 5-15 DEGREES ABOVE AVERAGE IN MOST
CASES, AND LIKELY 20+ DEGREES ABOVE AVERAGE ACROSS PARTS OF THE
UPPER MIDWEST ON THURSDAY. THIS ALSO HOLDS TRUE GOING INTO THE
WEEKEND, ALTHOUGH NEW ENGLAND AND THE MID-ATLANTIC REGION LIKELY
REMAIN CLOSER TO SEASONAL AVERAGES. THE NEXT ROUND OF ARCTIC COLD
LIKELY ARRIVES ACROSS MONTANA ON SUNDAY AND EXTENDS INTO THE
DAKOTAS BY MONDAY, WITH HIGHS POTENTIALLY 15-25 DEGREE BELOW
AVERAGE IN MANY CASES.
TATE/HAMRICK
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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