021
FXUS02 KWBC 101834
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
134 PM EST FRI JAN 10 2025
VALID 12Z MON JAN 13 2025 - 12Z FRI JAN 17 2025
.. ARCTIC AIRMASS TO REINFORCE EAST OF THE ROCKIES NEXT WEEK
..OVERVIEW
BY MONDAY, THE UPPER LEVEL PATTERN IS EXPECTED TO FEATURE AN
ELONGATED TROUGH FROM THE GREAT LAKES SOUTHWESTWARD INTO THE
CENTRAL ROCKIES AND SOUTHWEST U.S., THAT THEN QUICKLY SPLITS OFF
TUESDAY INTO WEDNESDAY, DEPOSITING AN UPPER LOW OFFSHORE SOUTHERN
CALIFORNIA. AS A RESULT, A RIDGE BUILDS OVER THE NORTHWEST AND THE
NORTHERN ROCKIES WHILE IN THE EAST, THE UPPER TROUGH SLIPS SLOWLY
SOUTHWARD OVER TIME.
THIS PATTERN EVOLUTION WILL LEAD TO COLD TEMPERATURES OVER THE
CENTRAL U.S. ON MONDAY AND SETTLING INTO THE EAST THEREAFTER, ALONG
WITH MULTIPLE DAYS OF LAKE EFFECT SNOW PLUS A COUPLE POTENTIAL
EPISODES OF SYNOPTIC-SCALE SNOW OVER/NEAR THE GREAT LAKES IN
ASSOCIATION SURFACE LOWS/FRONTAL SYSTEMS. TOWARD THE END OF THE
WEEK SOME PACIFIC SHORTWAVE ENERGY ROUNDING THE RIDGE SHOULD BEGIN
TO AMPLIFY INTO THE NORTHWEST AND/OR NORTHERN PLAINS WHILE THE
OFFSHORE UPPER LOW OPENS UP AND EJECTS INLAND.
..GUIDANCE/PREDICTABILITY ASSESSMENT
IN GENERAL, THE LATEST MODEL GUIDANCE SHOWED FAIRLY GOOD AGREEMENT
FOR THE LARGE SCALE PATTERN ACROSS THE CONUS. AS NOTED IN THE
PREVIOUS CYCLE, THE 00 UTC CMC WAS AN OUTLIER AND EXCLUDED FROM
THE MODEL PREFERENCES, AS ITS DEPICTION WITH THE UPPER TROUGH
SPLITTING OFF IN THE SOUTHWEST/CALIFORNIA WAS MUCH SLOWER (NOTING
THAT THE UPDATED/12Z UTC SOLUTION IS MORE AGREEABLE AT LEAST IN THE
EARLY PERIODS).
OTHERWISE, GUIDANCE HAS REASONABLE AGREEMENT BUT ALSO TYPICAL
SPREAD FOR THE PERIOD WITH THE EVOLUTION ACROSS THE NORTHERN
PLAINS AND UPPER MIDWEST. SEVERAL SHORTWAVE TROUGHS WILL WORK
THROUGH THE BROAD TROUGHING OVER THE CENTRAL TO EASTERN U.S. WHILE
THE CUTOFF UPPER LOW OFF CALIFORNIA REMAINS IN PLACE. TOWARD THE
END OF THE PERIOD, THE RIDGING OVER THE NORTHWEST BEGINS TO BREAK
DOWN AS SHORTWAVE ENERGY DIGS SOUTHWARD, GIVING WAY TO A STRONGER
SURGE OF ARCTIC AIR DROPPING INTO THE NORTHERN ROCKIES TOWARD THE
END OF THE FORECAST PERIOD (AND EXTENDING INTO NEXT WEEKEND). THE
WPC MODEL BLEND PREFERENCES LEANED MOSTLY ON THE GFS/ECMWF AND THE
ENSEMBLE MEANS FOR THE BULK OF THE PERIOD WITH SOME INCLUSION OF
THE UKMET EARLY ON. THIS LED TO GOOD CONTINUITY FROM THE PREVIOUS
CYCLE.
..WEATHER/HAZARDS HIGHLIGHTS
THE FORECAST PATTERN WILL SUPPORT ANOTHER SURGE OF ARCTIC AIR THAT
SHOULD PROGRESS FROM THE CENTRAL U.S. EARLY IN THE WEEK TO THE
EAST/SOUTHEAST BY TUESDAY-THURSDAY. OF PARTICULAR NOTE, EXPECT
AREAS OF HAZARDOUS COLD OVER THE FAR NORTHERN PLAINS MONDAY-TUESDAY
AND THEN MOST OF THE SOUTHERN HALF OR SO OF THE EAST BY TUESDAY-
THURSDAY. WITHIN THESE AREAS TEMPERATURES SHOULD BE 10-20F BELOW
NORMAL WITH EVEN COLDER WIND CHILLS. A FEW LOCATIONS AROUND THE
UPPER OHIO VALLEY/CENTRAL APPALACHIANS COULD CHALLENGE DAILY
RECORDS FOR COLD HIGHS ON TUESDAY. COLD CYCLONIC FLOW WILL PROMOTE
PERIODS OF LAKE EFFECT SNOW, SOME OF IT HEAVY, WHILE SEPARATE LOW
PRESSURE/FRONTAL SYSTEMS ON MONDAY AND THEN AFTER MIDWEEK MAY
PRODUCE BROADER COVERAGE OF AT LEAST LIGHT SNOW OVER THE GREAT
LAKES AND VICINITY.
ELSEWHERE, A WAVY FRONT CROSSING THE GULF OF MEXICO ON MONDAY MAY
PRODUCE RAIN OF VARYING INTENSITY OVER FLORIDA, WHILE SOME MOSTLY
LIGHT RAIN MAY EXTEND INTO SOUTHERN TEXAS FOR A TIME. UPPER RIDGING
THAT BUILDS OVER THE WEST THROUGH THURSDAY SHOULD KEEP MOST OF THE
REGION DRY. SOME LIGHT PRECIPITATION MAY REACH THE NORTHEAST BY
LATE WEEK WITH THE ARRIVAL OF A FRONT. AN UPPER LOW CLOSING OFF TO
THE WEST/SOUTHWEST OF SOUTHERN CALIFORNIA MAY PRODUCE SCATTERED
LIGHT PRECIPITATION OVER THE SOUTHWEST/FOUR CORNERS BY LATE WEEK AS
IT OPENS UP AND EJECTS INLAND, THOUGH LATEST TRENDS HAVE BEEN
LIGHTER AND SLOWER TO DEVELOP THIS ACTIVITY. MOSTLY BELOW NORMAL
TEMPERATURES OVER THE WEST WILL GRADUALLY MODERATE TO NEAR/SLIGHTLY
ABOVE NORMAL INTO THURSDAY, FOLLOWED BY A COOLER TREND IN THE
NORTHWEST ON FRIDAY. WARMEST TEMPERATURE ANOMALIES NEXT WEEK SHOULD
BE OVER THE NORTHERN PLAINS/UPPER MIDWEST DURING WEDNESDAY-FRIDAY
WITH SOME LOCATIONS 10-20F OR SO ABOVE NORMAL.
RAUSCH/TAYLOR
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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