924
FXUS02 KWBC 091850
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 PM EST THU JAN 9 2025
VALID 12Z SUN JAN 12 2025 - 12Z THU JAN 16 2025
.. ARCTIC AIRMASS TO REINFORCE OVER THE LOWER 48 NEXT WEEK
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
THE OVERALL PATTERN THROUGHOUT THE MEDIUM RANGE PERIOD (SUNDAY JAN
12 - THURSDAY JAN 16) IS GENERALLY WELL HANDLED ACROSS THE
GUIDANCE WITH DIFFERENCES LIMITED TO THE USUAL LESS PREDICTABLE
SPECIFICS SUCH AS INDIVIDUAL SHORTWAVE TIMING. FOLLOWING A MORE
ACTIVE PATTERN WITH SOUTHWESTERLY UPPER FLOW ACROSS THE CENTRAL-
EASTERN U.S., A NORTHERN-STREAM UPPER-LOW WILL SHIFT SOUTHWARD FROM
SOUTH-CENTRAL CANADA TO SOUTHEASTERN CANADA/THE GREAT LAKES/THE
NORTHEASTERN U.S. HELPING TO REINFORCE BROAD MEAN UPPER- LEVEL
TROUGHING AND RENEW A VERY CHILLY WINTER PATTERN. PRECIPITATION
CHANCES ARE LIKELY ACROSS THE GREAT LAKES, WITH A TREND FOR HIGHER
QPF SPECIFICALLY FOR FAVORABLE LAKE-EFFECT REGIONS FOLLOWING THE
INITIAL INCOMING SYSTEM AND PERSISTENT NORTHWESTERLY FLOW
THEREAFTER. TO THE WEST, SHORTWAVE ENERGY MOVING SOUTHWARD ALONG
THE PERIPHERY OF THE EXPANDING UPPER-TROUGH TO THE EAST IS EXPECTED
TO CUT OFF OVER COASTAL CALIFORNIA UNDER THE DEVELOPMENT OF A
STRENGTHENING NORTHERN STREAM RIDGE BUILDING OVER THE PACIFIC
NORTHWEST/SOUTHWESTERN CANADA. THIS PATTERN IS EXPECTED TO REMAIN
IN PLACE THROUGH EARLY NEXT WEEK BEFORE THINGS GRADUALLY BEGIN TO
CHANGE MID-WEEK. DIFFERENCES IN THE GUIDANCE ALSO INCREASE BY THE
END OF THE PERIOD, WITH THE ECMWF/CMC FAVORING ADDITIONAL ENERGIES
HELPING TO REINFORCE THE UPPER-TROUGH OVER THE CENTRAL/EASTERN
U.S., AND THE ECMWF/GFS INDICATING SOME EVENTUAL EASTWARD PROGRESS
OF THE WESTERN CUTOFF LOW WHILE THE CMC REMAINS FURTHER OFFSHORE.
THESE TRENDS WOULD FAVOR COLDER TEMPERATURES FOR THE EASTERN U.S.
WITH MORE PERSISTENT, STRONGER TROUGHING AND AN UPTICK IN
PRECIPITATION CHANCES OVER THE FOUR CORNERS REGION WITH EASTWARD
MOVEMENT OF THE UPPER-LOW. THE GFS IS ALSO MORE AGGRESSIVE IN
BRINGING AN UPPER-TROUGH OVER THE NORTHEASTERN PACIFIC SOUTHWARD TO
THE PACIFIC NORTHWEST WHILE THE CMC AND ECMWF REMAIN FURTHER
NORTH, WHICH WOULD IMPACT POTENTIAL PRECIPITATION CHANCES FOR THE
REGION.
THE UPDATED WPC FORECAST BEINGS WITH A COMPOSITE BLEND OF THE
00/06Z DETERMINISTIC GUIDANCE GIVEN GOOD AGREEMENT. A CONTRIBUTION
FROM THE ENSEMBLE MEANS IS GRADUALLY INCREASED IN THE MID- TO LATE
PERIOD AS DIFFERENCES INCREASE, AND MOSTLY IN EXPENSE OF THE
GFS/CMC OVER THE ECMWF GIVEN THE NOTED OUTLIER NATURE OF THESE
MODELS CONCERNING CERTAIN PARTS OF THE FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
LOW PRESSURE SYSTEM TRANSLATION AND UPPER SUPPORT SHOULD FAVOR
LIGHT TO MODERATE ORGANIZED SNOWS EXPECTED TO SLOWLY WORK OVER THE
MIDWEST AND GREAT LAKES EARLY NEXT WEEK, AND ALSO LEADING TO THE
TRIGGERING OF ADDITIONAL POTENTIALLY HEAVY LAKE EFFECT SNOWS. IN
THE WAKE OF THIS SYSTEM, ANOTHER REINFORCING BLAST OF ARCTIC AIR IS
FORECAST TO SPILL INTO THE NORTH-CENTRAL U.S. AND SPREAD TO THE
EAST AND SOUTHEAST NEXT WEEK. HAZARDOUS COLD TEMPERATURES ARE
EXPECTED FROM THE NORTHERN PLAINS TO THE GULF AND SOUTHEAST COASTS,
WITH TEMPERATURE ANOMALIES POTENTIALLY REACHING 10-20 DEGREES
BELOW NORMAL AND EVEN MORE FRIGID WIND CHILLS.
SOME MODERATE TO LOCALLY HEAVY SHOWERS WILL BE POSSIBLE LATE THIS
WEEKEND INTO EARLY NEXT WEEK ALONG THE IMMEDIATE GULF COAST AND
FLORIDA AS A COLD FRONT PASSES THROUGH THE REGION. SOME GULF
MOISTURE MAY RETURN FAR ENOUGH NORTHWARD TO BRING SHOWERS TO
SOUTHERN TEXAS BY THE MIDDLE OF NEXT WEEK. FOLLOWING SOME LIGHT TO
MODERATE SNOW SHOWERS FOR PORTIONS OF THE NORTHERN ROCKIES SUNDAY,
THE WEST WILL BE MOSTLY DRY INTO EARLY NEXT WEEK AS UPPER-LEVEL
RIDGING BUILDS OVER THE REGION. EASTWARD PROGRESSION OF AN UPPER-
LEVEL CUT-OFF LOW OVER COASTAL CALIFORNIA MAY BRING RENEWED
PRECIPITATION CHANCES TO THE FOUR CORNERS REGION MID-WEEK.
PUTNAM
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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