702
FXUS02 KWBC 241858
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
158 PM EST FRI JAN 24 2025
VALID 12Z MON JAN 27 2025 - 12Z FRI JAN 31 2025
..OVERVIEW
THE FORECAST PERIOD FOR NEXT WEEK BEGINS WITH A SLOW-MOVING CLOSED
LOW OVER CALIFORNIA AND BROAD CYCLONIC FLOW ALOFT FROM THE
NORTHERN PLAINS TO THE NORTHEAST STATES, WITH A SPLIT UPPER LEVEL
FLOW PATTERN IN PLACE. THE CLOSED LOW MAKES SLOW EASTWARD PROGRESS
THROUGH THE MIDDLE OF THE WEEK, WHILE A RIDGE AXIS BUILDS NORTH
INTO THE NORTHWEST AND A TROUGH REMAINS OVER THE NORTHEASTERN
QUADRANT OF THE COUNTRY. IT APPEARS LIKELY THAT SURFACE
CYCLOGENESIS WILL TAKE PLACE OVER THE SOUTHERN PLAINS IN RESPONSE
TO THE APPROACHING UPPER LOW, AND THIS WILL LIKELY FUEL AN INCREASE
IN RAIN FROM TEXAS TO PORTIONS OF THE DEEP SOUTH FOR THE END OF
THE WEEK. WINTRY WEATHER IS POSSIBLE ON THE WESTERN AND NORTHERN
SIDES OF THE PRECIPITATION SHIELD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS IN GOOD AGREEMENT EARLY-MID FORECAST PERIOD, AND
A MULTI-MODEL DETERMINISTIC BLEND WORKED WELL TO SMOOTH OUT MINOR
DIFFERENCES WITH SHORTWAVES AND EMBEDDED SURFACE LOWS. RECENT
MODELS ARE INDICATING A STRONGER SURFACE FRONTAL LOW TRACKING
THROUGH THE UPPER MIDWEST TO GREAT LAKES AND/OR NEARBY SOUTHERN
CANADA AROUND TUESDAY-WEDNESDAY COMPARED TO THE PREVIOUS FORECAST,
ALONG WITH SOME FRONTAL TIMING DIFFERENCES THAT ARE FAIRLY TYPICAL
FOR THE MID-MEDIUM RANGE PERIOD.
MODEL DIFFERENCES INCREASE BY LATE NEXT WEEK WITH THE SOUTHWEST
UPPER LOW. SOME MODELS LINGER THE UPPER LOW NEAR THE U.S./MEXICO
BORDER THROUGH SATURDAY, NAMELY THE GFS AND CMC RUNS, WHILE THE 00Z
ECMWF AND AI/ML RUNS ARE FASTER TO LIFT THE UPPER LOW
NORTHEASTWARD. THIS WILL AFFECT THE PLACEMENT OF THE SURFACE LOW
PRESSURE/FRONTAL SYSTEM IN THE SOUTH-CENTRAL U.S., WITH THE GFS/CMC
MORE SUPPRESSED AND THE 00Z ECMWF TRACKING MUCH FARTHER NORTHEAST,
AND IN TURN AFFECT THE PRECIPITATION AMOUNTS AND PLACEMENT. THIS
WPC FORECAST FAVORS THE MORE PROGRESSIVE SIDE OF THE GUIDANCE,
WHICH WAS CLOSER TO THE PREVIOUS FORECAST AND THE ENSEMBLE MEANS,
BUT NOT TO THE EXTENT OF THE 00Z ECMWF THAT BECAME FAR NORTHEAST
WITH THE SURFACE LOW. THE NEWER 12Z ECMWF HAS COME IN
SLOWER/FARTHER SOUTHWEST THAN THE 00Z RUN. ENSEMBLE MEANS SHOWED A
MORE REASONABLE MIDDLE GROUND WITH THE GEFS MEAN MORE PROGRESSIVE
THAN THE DETERMINISTIC GFS RUNS, WHILE THE EC MEAN WAS SOUTHWEST OF
THE 00Z EC. THUS BY DAY 6-7 QUICKLY RAMPED UP THE PROPORTION OF
ENSEMBLE MEANS IN THE FORECAST BLEND AS THE DETERMINISTIC MODELS
DIVERGED.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER LOW THROUGH MOVING SLOWLY THROUGH CALIFORNIA INTO MONDAY
COULD PROVIDE SOME LINGERING SHOWERS EARLY IN THE DAY, BUT
TAPERING OFF COMPARED TO THE RAIN AMOUNTS AND RATES SEEN OVER THE
WEEKEND, SO NO AREA SEEMS WARRANTED IN THE ERO. LIGHT TO MODERATE
SNOW IS POSSIBLE IN HIGHER ELEVATIONS OF SOUTHERN CALIFORNIA INTO
THE SOUTHWEST PARTICULARLY MONDAY. SOME MOISTURE COULD POOL ALONG A
FRONT IN THE SOUTH-CENTRAL TO SOUTHEASTERN U.S. FOR SOME LIGHT TO
MODEST RAIN MONDAY-TUESDAY.
THEN THE UPPER LOW THAT SLOWLY APPROACHES THE SOUTHERN PLAINS WILL
PROVIDE SUPPORT FOR NUMEROUS SHOWERS AND POSSIBLY THUNDERSTORMS
DEVELOPING FROM CENTRAL TEXAS TO THE LOWER MISSISSIPPI VALLEY
THROUGH LATE WEEK. THE CURRENT FORECAST SHOWS RAINFALL AMOUNTS
MAXIMIZING IN THE ARK-LA-TEX REGION AT 2 TO 4 INCHES PEAKING
THURSDAY. MEANWHILE, PROBABILITIES ARE INCREASING FOR WINTRY
WEATHER NORTH AND WEST OF THE HEAVIEST RAIN, INCLUDING SNOW IN THE
SOUTH-CENTRAL ROCKIES AND HIGH PLAINS AND SOME EMERGING CHANCE OF
FREEZING RAIN. MODEL SPREAD FOR THIS SYSTEM REMAINS HIGH THOUGH, SO
STAY TUNED FOR UPDATES TO THE FORECAST.
ELSEWHERE, SNOW IS POSSIBLE ACROSS THE GREAT LAKES TO NORTHEAST
WITH A CLIPPER SYSTEM OR TWO MONDAY-WEDNESDAY, WITH LAKE
ENHANCEMENT AS WELL AS TERRAIN ENHANCEMENT IN PLACES LIKE THE
ADIRONDACKS. BY LATE NEXT WEEK, NORTHERN STREAM TROUGHING IN THE
EASTERN PACIFIC MAY DIRECT MOISTURE ONSHORE TO THE WEST COAST FOR
RAIN AND HIGHER ELEVATION SNOW.
MUCH OF THE EAST SHOULD FINALLY BE BACK UP TOWARDS NORMAL
TEMPERATURES EARLY NEXT WEEK, THOUGH HIGHS A FEW DEGREES BELOW
NORMAL ARE POSSIBLE ACROSS THE SOUTHEAST ON MONDAY. ANOMALOUSLY
COOL TEMPERATURES WILL ALSO DEVELOP ACROSS THE SOUTHWESTERN U.S.
UNDER THE INFLUENCE OF UPPER TROUGHING/CLOSED LOW. THE NORTHEAST
U.S. SHOULD ALSO COOL BACK DOWN TO BELOW AVERAGE BY THE LATTER HALF
OF NEXT WEEK AFTER ANOTHER COLD FRONTAL PASSAGE. MEANWHILE THE
NORTHERN PLAINS TO MIDWEST ARE FORECAST TO SEE TEMPERATURES OF
10-20 DEGREES ABOVE AVERAGE, WHILE PERIODS OF ABOVE NORMAL
TEMPERATURES STRETCH THROUGH THE REST OF THE PLAINS INTO THE
MISSISSIPPI AND OHIO/TENNESSEE VALLEYS.
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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