651
FXUS02 KWBC 030746
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
246 AM EST SAT JAN 3 2026
VALID 12Z TUE JAN 06 2026 - 12Z SAT JAN 10 2026
..OVERVIEW
THE UPPER LEVEL PATTERN OVER THE CONUS WILL GRADUALLY TURN
INCREASINGLY MORE AMPLIFIED BY NEXT WEEKEND. ZONAL FLOW INITIALLY
WILL BE DOMINATED BY PROGRESSIVE NORTH-CENTRAL TO NORTHEASTERN U.S>
CLIPPER SYSTEMS. TROUGHING OFF THE WEST COAST MAY CLOSE OFF INTO
AN UPPER LOW OFF CALIFORNIA BEFORE IT MOVES INTO THE SOUTHWEST MID
WEEK 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, 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 INTO THE EAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE MODEL GUIDANCE GENERALLY SHOWS GOOD AGREEMENT ON THE OVERALL
PATTERN EVOLUTION OVER THE CONUS, BUT PLENTY OF UNCERTAINTY IN THE
DETAILS WHICH IMPACT SURFACE REFLECTIONS/FRONTAL TIMING AND
PLACEMENT AND SENSIBLE WEATHER. NORTHERN STREAM SHORTWAVES THROUGH
THE INITIALLY ZONAL FLOW FROM THE MIDWEST TO THE NORTHEAST SHOW
SOME VARIABILITY IN TIMING, BUT CAN MOSTLY BE HANDLED BY A MULTI-
MODEL BLEND.
THE GREATEST SOURCE OF FORECAST UNCERTAINTY REMAINS WITH A
SHORTWAVE OR CLOSED LOW ENTERING THE SOUTHWEST BY WEDNESDAY. EVEN
THROUGH THE NEW 00Z GUIDANCE FOR TONIGHT, THE CMC REMAINS ON THE
FASTER SIDE. ECMWF, GFS, AND UKMET ARE SLOWER, AS ARE THE AI
MODELS, INCREASING CONFIDENCE THAT THE CMC IS TOO FAST RIGHT NOW.
00Z ECMWF SLOWED DOWN FROM ITS PREVIOUS RUN, BUT THE 00Z GFS SPED
UP, SO THERE REMAINS A LOT OF RUN TO RUN VARIABILITY IN TIMING.
GENERALLY, A BLEND OF THESE TWO PIECES OF GUIDANCE WORKS AS A GOOD
STARTING POINT AND 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/PIECES OF
ENERGY EMBEDDED WITHIN THE LARGER TROUGH. OPTED TO BLEND IN MORE
ENSEMBLE MEANS THE LATTER HALF OF THE PERIOD TO HELP MITIGATE THESE
DIFFERENCES FOR NOW.
..WEATHER/HAZARDS HIGHLIGHTS
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. MEANWHILE, NORTHERN
STREAM ENERGY DROPPING INTO THE NORTHWEST WILL BRING MODERATE TO
LOCALLY HEAVY RAIN AND MOUNTAIN SNOW ON TUESDAY, BUT DRY ANTECEDENT
CONDITIONS SHOULD LIMIT ANY SORT OF FLASH FLOOD THREAT.
AS THE SOUTHERN STREAM SYSTEM MOVES EASTWARD TUESDAY INTO
WEDNESDAY, IT WILL SPREAD PRECIPITATION ACROSS THE INTERMOUNTAIN
WEST AND THE SOUTHWEST. THOUGH MOISTURE ANOMALIES ARE WELL ABOVE
NORMAL, THE LACK OF INSTABILITY AND PROGRESSIVE NATURE OF THIS
SYSTEM PRECLUDES THE NEED FOR A MARGINAL RISK AT THIS TIME ON THE
DAY 5/WEDNESDAY EXCESSIVE RAINFALL OUTLOOK. THIS SHORTWAVE,
COMBINED WITH PHASING TROUGHING ACROSS THE WEST MID-WEEK, COULD TAP
INTO GULF MOISTURE AND LEAD TO INCREASING RAIN CHANCES ACROSS THE
SOUTH-CENTRAL PLAINS INTO THE MIDWEST/OHIO VALLEY AND MID-SOUTH BY
THURSDAY-FRIDAY. WINTRY PRECIP IS POSSIBLE ON THE WESTERN AND
NORTHERN SIDES OF THE PRECIPITATION SHIELD, BUT WITH A LOT OF
UNCERTAINTY STILL.
TEMPERATURES ARE LIKELY TO BE WELL ABOVE AVERAGE ACROSS THE
ENTIRETY OF THE COUNTRY EAST OF THE ROCKIES. 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, WITH MUCH OF THE PLAINS BEGINNING TO MODERATE BACK TO NORMAL
BY FRIDAY AND SATURDAY. THE WEST/SOUTHWEST SHOULD TREND COLDER
NEXT WEEK AS THE PATTERN TURNS MORE AMPLIFIED AND TROUGHING
DEVELOPS.
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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