601
FXUS02 KWBC 300634
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
134 AM EST TUE DEC 30 2025
VALID 12Z FRI JAN 2 2026 - 12Z TUE JAN 6 2026
..GENERAL OVERVIEW
BROAD CYCLONIC FLOW ALOFT WILL BE IN PLACE ACROSS THE EASTERN HALF
OF THE COUNTRY FOR THE END OF THIS WEEK, WITH A DEEP LOW PRESSURE
SYSTEM CENTERED OVER HUDSON BAY AND ANOTHER OVER NEWFOUNDLAND.
MEANWHILE, AN UPPER RIDGE WILL INITIALLY BE IN PLACE ACROSS THE
INTERMOUNTAIN WEST, AND THEN REACH THE PLAINS OVER THE WEEKEND. AN
UNSETTLED WEATHER PATTERN EVOLVES ACROSS THE WEST COAST BY THE END
OF THE WEEK, WITH A WELL ORGANIZED STORM SYSTEM REACHING CENTRAL
AND NORTHERN CALIFORNIA INTO OREGON FRIDAY INTO EARLY SATURDAY.
ACROSS THE SOUTHERN TIER STATES, A WAVE OF LOW PRESSURE DEVELOPS
ALONG A FRONTAL BOUNDARY AND BRINGS HIGHER RAINFALL CHANCES FROM
THE DEEP SOUTH TO THE SOUTHEAST COAST ON FRIDAY. ANOTHER CLIPPER
SYSTEM IS LIKELY TO CROSS THE UPPER MIDWEST AND GREAT LAKES TOWARDS
EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE HAS REMAINED IN GOOD AGREEMENT WITH THE GENERAL
SYNOPTIC PATTERN ACROSS THE CONTINENTAL U.S. THROUGH THE END OF
THE WEEK INTO SATURDAY, FEATURING BROAD UPPER-TROUGHING ACROSS THE
CENTRAL TO EASTERN U.S. AND AN UPPER-RIDGE OVER THE WESTERN U.S.
THE GUIDANCE HAS ALSO CONTINUED TO CONVERGE ON A SOLUTION FEATURING
AN UPPER LEVEL WAVE INTERACTING WITH A LINGERING FRONTAL BOUNDARY
FROM THE SOUTH-CENTRAL TO SOUTHEASTERN U.S., WITH A SURFACE LOW
PASSING THROUGH THE REGION AND MOIST RETURN FLOW SUPPORTING AN
EXPANDING AREA OF PRECIPITATION EAST TOWARDS THE ATLANTIC COAST
FRIDAY AND INTO THE EARLY WEEKEND. THE NBM QPF IS A REASONABLE
COMPROMISE SOLUTION FOR COVERAGE AND AMOUNTS, AND A GENERAL
DETERMINISTIC BLEND FOR FRONTS AND PRESSURES.
UNCERTAINTY INCREASES ACROSS THE WESTERN U.S. AS THE FLOW IS
EXPECTED TO FLATTEN MORE AND SHORTWAVES APPROACH THE WEST COAST
AND PASS THROUGH THE REGION. RAIN AND SNOW AMOUNTS IN THE NBM QPF
HAVE TRENDED UP OVER THE LAST COUPLE OF DAYS, AND THIS IS A GOOD
COMPROMISE AS DIFFERENCES IN COVERAGE AND AMOUNTS IN THE OTHER
GUIDANCE INCREASE. FINALLY, MUCH OF THE GUIDANCE IS SUGGESTIVE OF
ANOTHER CLIPPER-TYPE SYSTEM DROPPING SOUTHEASTWARD ACROSS THE
GREAT LAKES AND VICINITY SUNDAY INTO MONDAY. THE BLEND OF THE
GFS/ECMWF AND ENSEMBLE MEANS REPRESENTED TIMING DIFFERENCES WELL
AND THE WPC QPF FORECAST WAS ONCE AGAIN INCREASED ACROSS THIS
REGION AS THE NBM REMAINED RATHER DRY.
..WEATHER/HAZARDS HIGHLIGHTS
A MORE ACTIVE WEATHER PATTERN DEVELOPS ALONG THE WEST COAST BY
FRIDAY AS A ORGANIZED LOW PRESSURE SYSTEM LIFTS NORTHWARD WITH A
COLD FRONT REACHING THE CALIFORNIA COAST. AN ATMOSPHERIC RIVER
WILL LIKELY AFFECT THE NORTHERN CALIFORNIA COAST AND MOVE INLAND
THROUGH SATURDAY AFTERNOON, BRINGING THE POTENTIAL FOR 2 TO 4
INCHES OF RAINFALL FOR THE LOWER ELEVATIONS, WITH A SECONDARY
MAXIMA FOR THE EASTERN FOOTHILLS OF THE NORTHERN SIERRA NEVADA. A
MARGINAL RISK AREA WILL BE VALID HERE FOR BOTH FRIDAY AND SATURDAY,
WITH POSSIBLE FUTURE UPGRADES TO SLIGHT RISK IN LATER OUTLOOKS IF
TRENDS CONTINUE HEAVIER IN FUTURE MODEL CYCLES.
ELSEWHERE ACROSS THE COUNTRY, AN AREA OF LOW PRESSURE IS EXPECTED
TO DEVELOP ACROSS THE DEEP SOUTH AND THEN EXIT THE SOUTHEAST COAST
SATURDAY, PRODUCING A CORRIDOR OF MODERATE RAINFALL AND SOME
THUNDERSTORMS FROM LOUISIANA TO THE CAROLINAS, PERHAPS REACHING AS
FAR NORTH AS VIRGINIA. ANOTHER CLIPPER TYPE SYSTEM IS LIKELY TO
TRACK FROM THE UPPER MIDWEST TO NEW ENGLAND SUNDAY INTO MONDAY WITH
A SWATH OF MAINLY LIGHT SNOW AND PERHAPS SOME MIXED WINTRY
PRECIPITATION ALONG THE SOUTHERN PORTION OF IT, BUT NOT CURRENTLY
EXPECTED TO BE AN IMPACTFUL SYSTEM.
IN TERMS OF TEMPERATURES, THERE WILL LIKELY BE A LITTLE BIT OF AN
ABATEMENT OF THE COLD TEMPERATURES ACROSS THE NORTHERN TIER STATES
AS THE UPPER TROUGH FLATTENS SOME AND THE AIRMASS MODIFIES, WITH
READINGS SLIGHTLY BELOW NORMAL AND THE GREATEST ANOMALIES LIKELY
OVER NORTHERN NEW ENGLAND. ABOVE AVERAGE TEMPERATURES ARE EXPECTED
TO ENCOMPASS A LARGE PORTION OF THE U.S. FROM THE INTERMOUNTAIN
WEST TO THE PLAINS AND DEEP SOUTH, AND CLOSER TO AVERAGE FROM THE
OHIO VALLEY TO THE MID-ATLANTIC REGION.
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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