678
FXUS02 KWBC 041928
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
228 PM EST SUN JAN 4 2026
VALID 12Z WED JAN 07 2026 - 12Z SUN JAN 11 2026
..OVERVIEW
QUASI-ZONAL FLOW OVER THE CONUS (AS A PROGRESSIVE CLIPPER SYSTEM
MOVES THROUGH THE NORTHEAST) AT THE START OF THE MEDIUM RANGE
PERIOD WEDNESDAY WILL TURN INCREASINGLY MORE AMPLIFIED BY LATE WEEK
INTO NEXT WEEKEND. A SOUTHERN STREAM UPPER LOW SHOULD PROGRESS
FROM THE EASTERN PACIFIC ACROSS SOUTHERN CALIFORNIA/NORTHERN MEXICO
AND WEAKEN WITH TIME AS IT PHASES WITH STRONG NORTHERN STREAM
ENERGY DROPPING INTO THE WEST. THIS WILL DEVELOP A DEEP TROUGH THAT
MOVES FROM THE WEST THURSDAY INTO THE CENTRAL U.S. FRIDAY AND MORE
SLOWLY TOWARD THE EAST NEXT WEEKEND. THE PATTERN WILL ALLOW FOR AN
INCREASE IN PRECIPITATION COVERAGE ACROSS THE CENTRAL TO EASTERN
U.S. LATER THIS WEEK, WHILE SHIFTING WELL ABOVE NORMAL TEMPERATURES
FROM THE PLAINS/MISSISSIPPI VALLEY INTO THE EAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE IS SHOWING INCREASING AGREEMENT FOR THE PATTERN
DESCRIBED ABOVE, THOUGH WITH STILL SOME UNCERTAINTY IN THE DETAILS.
INITIALLY WITH THE SOUTHERN STREAM CLOSED LOW OFF CALIFORNIA,
CONTINUE TO FAVOR THE SLOWER GUIDANCE LIKE THE GFS AND ECMWF
BECAUSE THEY AGREE BETTER WITH THE AI MODELS COMPARED TO THE CMC
AND UKMET. THEN, MODELS AGREE THAT ADDITIONAL STRONG VORTICITY WILL
DROP INTO THE NORTHWEST MID TO LATE WEEK, ACTING TO DEEPEN
TROUGHING OVER THE INTERIOR WEST WHILE THE SOUTHERN STREAM LOW
PHASES IN. HOWEVER, GUIDANCE HAS SHOWN MORE SPREAD WITH THE
STRENGTH OF THE ENERGY, LEADING TO HOW FAR SOUTH AND WEST THE
TROUGH DIGS BEFORE MOVING EASTWARD. THROUGH THE 00/06Z MODEL CYCLE,
THE ECMWF/AIFS/UKMET WERE ALL STRONGER WITH THIS, CAUSING THE
TROUGH TO BE FARTHER WEST/SLOWER THAN THE GFS. FAVORED THE SLOWER
CLUSTER AND FORTUNATELY THE NEW 12Z GFS HAS TRENDED TOWARD THIS.
THE TROUGH PATTERN LEADS TO A SURFACE LOW TRACK GENERALLY ACROSS
THE SOUTH-CENTRAL PLAINS TO UPPER GREAT LAKES LATE WEEK WITH SOME
BETTER CLUSTERING IN THE INCOMING 12Z GUIDANCE, BUT EVEN RELATIVELY
MINOR LOW TRACK SHIFTS COULD LEAD TO FORECAST DIFFERENCES IN
POTENTIAL IMPACTS LIKE SNOW TO THE LOW'S NORTHWEST. MODELS SHOW
ADDITIONAL ENERGY DROPPING INTO THE TROUGH AND REINFORCING IT BY
FRIDAY-SATURDAY, WITH BETTER AGREEMENT AT THIS POINT. THE PATTERN
IN THE WEST WILL MOSTLY FLIP TO STRONG RIDGING BY NEXT WEEKEND
BEHIND THE MAIN TROUGH, THOUGH THERE IS SOME UNCERTAIN POTENTIAL
FOR WEAK ENERGY TO UNDERCUT THE RIDGE TO SET UP A SOUTHERN STREAM
LOW ATOP NORTHERN MEXICO OR SO.
THE WPC FORECAST WAS BASED ON A ECMWF-HEAVY BLEND OF MODELS AND
ENSEMBLES, WITH INCREASING PROPORTIONS OF THE ENSEMBLE MEANS AS THE
PERIOD PROGRESSED. THE MAIN FORECAST TREND TODAY WAS TO INCREASE
PRECIPITATION IN THE NORTH-CENTRAL U.S. COMPARED TO THE NBM AND
CONTINUITY BECAUSE OF POSSIBLE SNOW BEHIND THE SURFACE LOW.
..WEATHER/HAZARDS HIGHLIGHTS
A CLIPPER SYSTEM MOVING INTO THE NORTHEAST ON WEDNESDAY WILL
SPREAD SOME PRECIPITATION THERE, INCLUDING LIGHT TO MODERATE SNOW
LINGERING. MEANWHILE, THE CLOSED LOW INITIALLY OFF SOUTHERN
CALIFORNIA SHOULD SPREAD SOME PRECIPITATION ACROSS THE SOUTHWEST,
BUT HEAVY RAINFALL IS NOT ANTICIPATED. RAIN AND MOUNTAIN SNOW WILL
ALSO OVERSPREAD THE PACIFIC NORTHWEST TO INTERMOUNTAIN WEST AS THE
FIRST SURGE OF ENERGY PRODUCES TROUGHING OVER THE REGION MIDWEEK.
HEAVY SNOW IS LIKELY FOR THE CASCADES, AND POSSIBLE FOR THE
NORTHERN ROCKIES.
AS THE SHORTWAVE AND THE LARGER SCALE TROUGH OVER THE WEST 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 STARTING WEDNESDAY NIGHT,
PRESSING EAST INTO THE OHIO/TENNESSEE VALLEYS THURSDAY-FRIDAY, AND
EVENTUALLY THE EAST FRIDAY-SATURDAY. FOR THURSDAY, A FAVORABLE
UPPER JET, MOISTURE ANOMALIES OVER THE 90TH PERCENTILE FOR THIS
TIME OF YEAR, AND SOME INSTABILITY REACHING AS FAR NORTH AS THE
OHIO VALLEY WILL SUPPORT CONVECTION CENTERED OVER THE MID-
MISSISSIPPI VALLEY AND VICINITY. MODEL QPFS SHOW 2-3 INCHES OF RAIN
WITH LOCALLY HIGHER AMOUNTS, SUPPORTING A MARGINAL RISK IN THE DAY
5/THURSDAY ERO, SINCE RAIN RATES MAY OVERCOME THE ANTECEDENT DRY
CONDITIONS FOR ISOLATED FLOODING. WINTRY PRECIPITATION REMAINS
POSSIBLE ON THE WESTERN AND NORTHERN SIDES OF THE PRECIPITATION
SHIELD. WHILE THE DETAILS ARE STILL UNCERTAIN DEPENDING ON THE
TRACK AND TIMING OF THE SURFACE LOW PRESSURE SYSTEM, SNOW GENERALLY
SEEMS POSSIBLE ACROSS PORTIONS OF THE NORTHERN/CENTRAL PLAINS INTO
THE MIDWEST THURSDAY NIGHT INTO FRIDAY AND FOR THE UPPER GREAT
LAKES REGION FRIDAY INTO SATURDAY.
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 WILL BE WIDESPREAD
ACROSS THE CENTRAL U.S. BY WEDNESDAY, AND WILL EXPAND EASTWARD
(THOUGH WITH SOME MODERATION) ACROSS THE MIDWEST INTO THE EAST.
DAILY RECORDS FOR WARM LOWS AND HIGHS COULD BE SET ACROSS THE
SOUTHERN TIER. MEANWHILE THE WEST/SOUTHWEST SHOULD BE NEARER TO
NORMAL OR SLIGHTLY BELOW AS THE PATTERN TURNS MORE AMPLIFIED AND
TROUGHING DEVELOPS, AND TEMPERATURES ARE LIKELY TO MODERATE BACK TO
NORMAL INTO THE PLAINS AND MISSISSIPPI VALLEY BY SATURDAY AND THE
EAST NEXT SUNDAY BEHIND A POTENT COLD FRONT JUST AHEAD OF THE UPPER
TROUGH.
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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