228
FXUS02 KWBC 011953
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 PM EST THU JAN 1 2026
VALID 12Z SUN JAN 04 2026 - 12Z THU JAN 08 2026
...MULTIPLE ROUNDS OF HEAVY RAIN AND MOUNTAIN SNOW FOR
CALIFORNIA...
..OVERVIEW
AN UPPER RIDGE OVER THE CENTRAL U.S. AT THE START OF THE MEDIUM
RANGE PERIOD SUNDAY WILL PROVIDE UNSEASONABLY WARM TEMPERATURES TO
THE PLAINS, AS WELL AS SEPARATE A TROUGH LIFTING OUT OF THE EASTERN
U.S. AND ANOTHER TROUGH IN THE EASTERN PACIFIC. THE PATTERN WILL
GENERALLY TRANSITION TO MORE ZONAL FLOW FOR THE FIRST HALF OF NEXT
WEEK, THOUGH WITH A COUPLE OF NORTH-CENTRAL TO NORTHEASTERN U.S.
CLIPPER SYSTEMS. THE EXCEPTION TO THE ZONAL FLOW WILL BE
TROUGHING/ENERGY DIVING INTO THE SOUTHERN STREAM ACROSS THE EASTERN
PACIFIC MOVING INTO CALIFORNIA AND THE SOUTHWEST. MULTIPLE ROUNDS
OF PRECIPITATION THAT COULD BE HEAVY ARE EXPECTED PARTICULARLY FOR
CALIFORNIA AHEAD OF AND UNDERNEATH THIS TROUGH/LOW, EVENTUALLY
SPREADING INTO THE SOUTH-CENTRAL U.S. BY THE MIDDLE OF NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD SYNOPTIC SCALE AGREEMENT WITH THE
PATTERN DESCRIBED ABOVE ACROSS THE LOWER 48 GOING INTO SUNDAY.
MODELS INDICATE THE EASTERN U.S. TROUGH LIFTING MONDAY, AND THEN
THE NORTHERN STREAM WILL BE DOMINATED BY SHORTWAVES. THESE COULD
MAKE A DIFFERENCE WITH SURFACE LOW/FRONTAL PLACEMENT AND
TEMPERATURES, BUT IT IS DIFFICULT TO PICK OUT OUTLIERS WITH THE
SHALLOW FLOW. THIS COULD ALL BE HANDLED WITH A MULTI-MODEL BLEND
FOR THE FORECAST.
THE MOST UNCERTAIN ASPECT OF THE FORECAST IS THE TROUGH PATTERN
ACROSS THE EASTERN PACIFIC TO WESTERN U.S., INITIALLY WITH
SHORTWAVE TIMING AND PLACEMENT BUT EVENTUALLY WITH THE BROADER
PATTERN AS NEXT WEEK PROGRESSES. SOUTHERN STREAM TROUGHING/A
POTENTIAL CLOSED LOW MOVING TOWARD AND INTO CALIFORNIA/THE
SOUTHWEST SHOWS TIMING DIFFERENCES BY TUESDAY-THURSDAY. THE 00Z AND
12Z ECMWF AND UKMET RUNS WERE ON THE FASTER SIDE WITH THIS TROUGH
MOVING EAST COMPARED TO THE LARGER CLUSTER OF THE AIFS AND AI-GFS
WITH THE DYNAMICAL GFS AND CMC RUNS. THUS LEANED AWAY FROM THE
EC/UK AS THE AI GUIDANCE WAS SLOWER. ON THE WHOLE, TRANSITIONED THE
MODEL BLEND TO INCLUDE MORE ENSEMBLE MEANS AS THE PERIOD
PROGRESSED, LESSENING THE EC/UK PROPORTION IN PARTICULAR, WITH THE
BLEND REACHING HALF MEANS BY THE END OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
SHORTWAVES ROUNDING THE EASTERN PACIFIC/WESTERN U.S. TROUGH WILL
PROVIDE SUPPORT FOR ROUNDS OF WEAK TO MODERATE ATMOSPHERIC RIVERS
CAUSING PRECIPITATION IN THE WEST INTO EARLY NEXT WEEK. ONE SUCH
MOISTURE PLUME ON SUNDAY COULD PRODUCE 1 TO LOCALLY 4 INCHES OF
RAINFALL FOR PORTIONS OF CALIFORNIA, WHICH COULD BE MOST IMPACTFUL
IN THE TRANSVERSE RANGES OF SOUTHERN CALIFORNIA GIVEN WET
ANTECEDENT CONDITIONS FROM RECENT AND SHORT RANGE HEAVY RAINS. THUS
WILL MAINTAIN A SLIGHT RISK THERE EMBEDDED WITHIN A MARGINAL
ACROSS MUCH OF CALIFORNIA FOR DAY 4/SUNDAY. YET ANOTHER BROAD
MOISTURE PLUME COULD AFFECT CALIFORNIA AGAIN BY MONDAY. RECENT
GUIDANCE IS MOSTLY FOCUSED ON NORTHERN TO CENTRAL CALIFORNIA FOR
HEAVY PRECIPITATION, BUT A FEW MODELS SHOW MODERATE QPF SOUTH TO
THE SENSITIVE TRANSVERSE RANGES. HAVE BLANKETED MUCH OF CALIFORNIA
IN A MARGINAL RISK AGAIN FOR DAY 5/MONDAY, BUT THIS MAY BE REFINED
IN FUTURE ISSUANCES. HEAVY SNOW IS LIKELY FOR THE HIGHER TERRAIN OF
THE SIERRA. MORE MODEST PRECIPITATION AMOUNTS ARE EXPECTED FARTHER
NORTH IN THE PACIFIC NORTHWEST AND FARTHER EAST INTO THE
INTERMOUNTAIN WEST. PRECIPITATION IS FORECAST TO CONTINUE INTO
TUESDAY ACROSS THE SOUTHWEST, WHILE A NORTHERN STREAM WAVE LEADS TO
INCREASING PACIFIC NORTHWEST PRECIPITATION AS WELL.
ELSEWHERE ACROSS THE COUNTRY, COUPLE OF CLIPPER SYSTEMS ARE
FORECAST TO TRACK FROM THE UPPER MIDWEST TO THE GREAT LAKES AND
THEN THE NORTHEAST DURING THE PERIOD, WITH ONE GENERALLY SUNDAY-
MONDAY AND ANOTHER TUESDAY-WEDNESDAY. THESE RELATIVELY WEAK SYSTEMS
COULD PRODUCE A SWATH OF MAINLY LIGHT SNOW AND PERHAPS SOME MIXED
WINTRY PRECIPITATION ALONG THE SOUTHERN PORTION OF ITS TRACK. ALSO
BY MIDWEEK, TROUGHING TRACKING INTO THE ROCKIES/HIGH PLAINS FROM
THE WEST COULD TAP INTO GULF MOISTURE AND LEAD TO INCREASING RAIN
CHANCES (AND PERHAPS SOME THUNDERSTORMS) ACROSS SOUTHERN/CENTRAL
PARTS OF THE PLAINS AND MISSISSIPPI VALLEY INTO THE MID-SOUTH.
TEMPERATURES ARE LIKELY TO BE MUCH WARMER THAN AVERAGE ACROSS A
WIDE EXPANSE OF THE COUNTRY THIS WEEKEND INTO MUCH OF NEXT WEEK,
ESPECIALLY ACROSS THE PLAINS, WHERE TEMPERATURE ANOMALIES OF 15 TO
30 DEGREES ABOVE AVERAGE WILL BE COMMON. THIS BRINGS HIGHS OF 70S
AND LOW 80S TO TEXAS AND 60S AS FAR NORTH AS WESTERN SOUTH DAKOTA
SUNDAY INTO MONDAY. DAILY RECORDS FOR WARM LOWS AND HIGHS COULD BE
SET ACROSS THE INTERMOUNTAIN WEST AND PLAINS. UNSEASONABLY WARM
TEMPERATURES WILL GRADUALLY SPREAD EASTWARD THROUGH THE WEEK,
BRINGING ANOMALIES OF +15 TO +25 DEGREES TO THE MISSISSIPPI VALLEY
AND EVENTUALLY +10 ANOMALIES TO THE EAST COAST, AFTER A COLDER THAN
AVERAGE START TO THE WEEK ACROSS THE NORTHEAST.
TATE
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page