306
FXUS02 KWBC 031947
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 PM EST SAT JAN 3 2026
VALID 12Z TUE JAN 06 2026 - 12Z SAT JAN 10 2026
..OVERVIEW
QUASI-ZONAL FLOW OVER THE CONUS (WITH PROGRESSIVE NORTH-CENTRAL TO
NORTHEASTERN U.S. CLIPPER SYSTEMS) AT THE START OF THE MEDIUM
RANGE PERIOD TUESDAY WILL TURN INCREASINGLY MORE AMPLIFIED BY LATE
WEEK INTO NEXT WEEKEND. SOUTHERN STREAM TROUGHING OFF THE WEST
COAST MAY CLOSE OFF INTO AN UPPER LOW OFF CALIFORNIA BEFORE IT
MOVES INTO THE SOUTHWEST MIDWEEK AND WEAKENS IN FAVOR OF ADDITIONAL
ENERGY DIVING DOWN THE WEST COAST LATE WEEK. THIS ENERGY SHOULD
HELP DEVELOP DEEPER TROUGHING MOVING THROUGH THE WEST INTO THE
CENTRAL U.S., WITH A STRENGTHENING RIDGE OVER THE EAST. THE PATTERN
WILL ALLOW FOR AN INCREASE IN PRECIPITATION COVERAGE ACROSS THE
CENTRAL U.S. FOR MID TO LATE WEEK, WHILE SHIFTING WELL ABOVE NORMAL
TEMPERATURES FROM THE PLAINS/MISSISSIPPI VALLEY INTO THE EAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS REASONABLY AGREEABLE WITH THE LARGE SCALE
PATTERN OVER THE LOWER 48 NEXT WEEK, BUT PLENTY OF UNCERTAINTY IN
THE DETAILS WHICH IMPACT SURFACE REFLECTIONS/FRONTAL TIMING AND
PLACEMENT AND SENSIBLE WEATHER. THE FIRST PRIMARY MODEL DIAGNOSTICS
ISSUE IS THE SOUTHERN STREAM TROUGH/POSSIBLE CLOSED LOW TIMING AS
IT ENTERS SOUTHERN CALIFORNIA/NORTHERN MEXICO LATE TUESDAY OR
WEDNESDAY AND TRACKS EAST. WITH BOTH THE 00/06Z AND THE NEW 12Z
MODEL CYCLE, THE ECMWF AND GFS ALONG WITH THE EC-AIFS AND AI-GFS
WERE PRETTY AGREEABLE IN SHOWING A SLOWER TRACK THAN THE UKMET AND
CMC. THUS WILL LEAN TOWARD THE FORMER CLUSTER WITH AN ECMWF/GFS
BLEND, AND THIS MAINTAINS GOOD CONTINUITY WITH THE PREVIOUS WPC
FORECAST.
AFTER THIS, MODELS AGREE THAT ADDITIONAL STRONG VORTICITY WILL
DROP INTO THE NORTHWEST MID TO LATE WEEK, ACTING TO DEEPEN
TROUGHING OVER THE WESTERN AND CENTRAL U.S., BUT WITH PLENTY OF
UNCERTAINTY IN THE DETAILS OF INDIVIDUAL SHORTWAVES EMBEDDED WITHIN
THE LARGER TROUGH. THIS IMPACTS THE RESULTING SURFACE LOW TRACK
(AND THUS WINTER PROBABILITIES). ONE TREND IN TODAY'S MODELS IS
THAT THE SURFACE LOW TRENDED NOTABLY SLOWER AS IT MOVES ACROSS THE
MIDWEST FRIDAY-SATURDAY, BUT STILL WITH AMPLE UNCERTAINTY IN THE
TRACK AND TIMING. ONE CAUSE OF THE UNCERTAINTY IS POSSIBLE
ADDITIONAL UPPER ENERGY DROPPING SOUTH FROM CANADA LATE WEEK. THE
12Z ECMWF AND AIFS HAVE THIS VORTICITY DIGGING INTO THE NORTHWEST
WHILE THE 12Z GFS/AI-GFS AND CMC SHOW IT MORE INTO THE PLAINS. AS
THE PERIOD PROGRESSED, THE WPC FORECAST BLENDED INCREASING
PROPORTIONS OF THE GEFS AND EC ENSEMBLE MEANS TO MITIGATE THESE
DIFFERENCES AND WILL CONTINUE TO MONITOR.
..WEATHER/HAZARDS HIGHLIGHTS
A CLIPPER SYSTEM MOVING ACROSS THE MIDWEST TO GREAT LAKES AND
NORTHEAST TUESDAY INTO WEDNESDAY WILL SPREAD SOME PRECIPITATION
THERE, INCLUDING POSSIBLE LIGHT FREEZING RAIN AND LIGHT TO MODERATE
SNOW IN SOME AREAS. MEANWHILE, ENERGY DROPPING SOUTH AND
DEVELOPING AN EASTERN PACIFIC/CALIFORNIA UPPER LOW WILL CONTINUE TO
BRING SOME GENERALLY LIGHT PRECIPITATION TO AN ALREADY VERY SOGGY
SOUTHERN CALIFORNIA. PRECIPITATION SHOULD BE LIGHT ENOUGH AND
MOVING QUICKLY SO NO FLOODING THREAT IS ANTICIPATED ON TUESDAY.
ADDITIONALLY, NORTHERN STREAM ENERGY DROPPING INTO THE NORTHWEST
WILL BRING MODERATE TO HEAVY PRECIPITATION TO THAT REGION ON
TUESDAY AND WEDNESDAY. COASTAL WASHINGTON AND OREGON COULD BE AT
RISK OF LOCALLY HEAVY RAIN AS A WEAK ATMOSPHERIC RIVER PUSHES
THROUGH ON TUESDAY, BUT THE QUICK MOVEMENT AND DRY ANTECEDENT
CONDITIONS SHOULD LIMIT THE FLOODING THREAT THERE. MEANWHILE THE
CASCADES CAN EXPECT HEAVY SNOW.
AS THE SOUTHERN STREAM SYSTEM MOVES EASTWARD INTO WEDNESDAY, IT
WILL SPREAD PRECIPITATION ACROSS THE SOUTHWEST. THOUGH MOISTURE
ANOMALIES ARE WELL ABOVE NORMAL, THE LACK OF INSTABILITY AND
PROGRESSIVE NATURE OF THIS SYSTEM PRECLUDES THE NEED FOR ANY
EXCESSIVE RAINFALL RISK IN THE DAY 5/WEDNESDAY ERO. THE BROAD
TROUGH IN THE WEST WILL ALSO PROVIDE SUPPORT FOR MODERATE SNOW
ACROSS MOUNTAIN AREAS. AS THE SHORTWAVE AND THE LARGER SCALE TROUGH
PHASE LATE WEDNESDAY INTO THURSDAY, THE COMBINED TROUGH SHOULD TAP
INTO GULF MOISTURE, LEADING TO RAIN CHANCES EXPANDING ACROSS THE
SOUTH-CENTRAL PLAINS AND MISSISSIPPI VALLEY WEDNESDAY NIGHT AND
PRESSING EAST INTO THE MIDWEST AND OHIO/TENNESSEE VALLEYS THURSDAY-
FRIDAY. WINTRY PRECIPITATION REMAINS POSSIBLE ON THE WESTERN AND
NORTHERN SIDES OF THE PRECIPITATION SHIELD IN THE NORTHERN/CENTRAL
PLAINS TO MIDWEST, BUT THIS WILL BE HIGHLY DEPENDING ON THE
UNCERTAIN TRACK AND TIMING OF THE SURFACE LOW PRESSURE SYSTEM.
TEMPERATURES ARE LIKELY TO BE WELL ABOVE AVERAGE ACROSS THE
ENTIRETY OF THE COUNTRY EAST OF THE ROCKIES BY MIDWEEK. TEMPERATURE
ANOMALIES OF 15 TO 30 DEGREES ABOVE AVERAGE TUESDAY TO THURSDAY
WILL BE COMMON ACROSS THE CENTRAL U.S. AND INTO THE MIDWEST AND
SOME DAILY RECORDS FOR WARM LOWS AND HIGHS COULD BE SET.
UNSEASONABLY WARM TEMPERATURES WILL GRADUALLY EXPAND AND SPREAD
EASTWARD LATER IN THE WEEK. MEANWHILE THE WEST/SOUTHWEST SHOULD
TREND COLDER NEXT WEEK AS THE PATTERN TURNS MORE AMPLIFIED AND
TROUGHING DEVELOPS, AND TEMPERATURES ARE LIKELY TO MODERATE BACK TO
NORMAL INTO THE PLAINS BY FRIDAY AND MISSISSIPPI VALLEY SATURDAY
AS THIS TROUGH MOVES EAST.
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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