015
FXUS02 KWBC 201904
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
204 PM EST MON JAN 20 2025
VALID 12Z THU JAN 23 2025 - 12Z MON JAN 27 2025
...BITTERLY COLD TEMPERATURES TO CONTINUE THROUGH THURSDAY FOR
PARTS OF THE EAST AND THE SOUTH...
..OVERVIEW
MEAN TROUGHING OVER THE CENTRAL U.S. ON THURSDAY WILL PROGRESS
EASTWARD AND CROSS THE EAST COAST BY THE WEEKEND. BEHIND THIS,
SOME WEAK UPPER RIDGING OR AT LEAST FLATTER FLOW SHOULD MOVE IN,
FINALLY HELPING TO MODERATE THE BITTERLY COLD LATE WEEK
TEMPERATURES ACROSS THE EAST AND SOUTH. A SHORTWAVE REACHING
WESTERN CANADA BY THURSDAY WILL SPLIT, SENDING NORTHERN STREAM
ENERGY THROUGH THE NORTHERN U.S. TIER/GREAT LAKES/NORTHEAST AS
TRAILING ENERGY DIVES SOUTH AND LIKELY FORMS A CLOSED LOW OVER OR
NEAR CALIFORNIA INTO THE SOUTHWEST THIS WEEKEND. THE UPPER LOW
SHOULD PERSIST INTO NEXT MONDAY, AND MAY BRING SOME MUCH NEEDED
PRECIPITATION TO PARTS OF SOUTHERN CALIFORNIA WHICH HAS BEEN
STRICKEN WITH DEVASTATING WILDFIRES LATELY. MEANWHILE A FRONT
REACHING THE MISSISSIPPI/TENNESSEE VALLEY REGION MAY SERVE TO
ENHANCE RAINFALL OVER PARTS OF THE SOUTHERN TIER AROUND THE START
OF NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
WITH GUIDANCE GRADUALLY CLUSTERING BETTER FOR THE SHORTWAVE
CROSSING THE CENTRAL/EASTERN PORTION OF THE COUNTRY FROM THURSDAY
INTO EARLY SATURDAY, THE PRIMARY FORECAST DISCREPANCIES INVOLVE THE
POTENTIAL UPPER LOW CLOSING OFF ALONG OR INLAND FROM THE WEST COAST
DURING THE WEEKEND AND THE CHARACTER OF NORTHERN STREAM TROUGHING
OVER THE CENTRAL/EASTERN U.S. BY NEXT MONDAY.
00Z/06Z GUIDANCE USED FOR THE UPDATED FORECAST, AS WELL AS NEW 12Z
RUNS, SHOW TYPICAL SPREAD FOR THE WESTERN UPPER LOW. ECMWF RUNS AND
THE ICON ARE NEAR THE CALIFORNIA COAST WHILE GFS/GEFS RUNS ARE MORE
INLAND. LATEST MACHINE LEARNING (ML) MODELS SHOW A SIMILAR SPREAD
THOUGH OVERALL WITH A LITTLE MORE TILT TOWARD THE WESTERN HALF OF
THE ENVELOPE. LATEST CMC RUNS HAVE BEEN SOMEWHAT ERRATIC, HOLDING
THE UPPER LOW NORTH OF CONSENSUS BY NEXT MONDAY IN THE 00Z RUN AND
THEN DELAYING CLOSED LOW FORMATION BY A DAY OR SO IN THE NEW 12Z
RUN. AN UPPER LOW PATH MOST SIMILAR TO THE 00Z ECENS MEAN PROVIDES
A REASONABLE INTERMEDIATE SOLUTION AT THIS TIME AND IS CLOSE TO
CONTINUITY.
FARTHER EAST, BY NEXT SUNDAY-MONDAY THE MODELS AND ENSEMBLES BEGIN
TO DIVERGE FOR THE AMPLITUDE AND TIMING OF NORTHERN STREAM
TROUGHING OVER PARTS OF THE CENTRAL AND/OR EASTERN U.S. GFS/GEFS
MEAN RUNS ARE FLATTEST, ECMWF RUNS LEAN SOMEWHAT ON THE AMPLIFIED
SIDE, AND THE CMC/CMCENS MEAN ARE MOST PROGRESSIVE. ML MODELS OFFER
GOOD SUPPORT FOR AN INTERMEDIATE SOLUTION BETWEEN THESE VARIOUS
EXTREMES, PERHAPS CLOSEST TO THE 00Z ECENS MEAN FOR AMPLITUDE AND
TIMING. SPECIFICS OF THIS TROUGH WILL AFFECT THE SURFACE FRONT AND
EMBEDDED WAVINESS REACHING THE SOUTHERN/EASTERN STATES BY THE START
OF NEXT WEEK, ALONG WITH PRECIPITATION DETAILS. DYNAMICAL/ML
CONSENSUS SUGGESTS THAT BY EARLY NEXT WEEK THE 13Z NBM AND EARLIER
GFS/GEFS RUNS MAY BE OVERDONE WITH AMOUNTS IN THE NORTHERN HALF OF
THE PRECIPITATION SHIELD AND LIGHT FARTHER SOUTH. PARTIAL
ADJUSTMENTS WERE MADE IN LIGHT OF CONSENSUS IDEAS, WITH LEEWAY FOR
ADDITIONAL TRENDS PENDING NEW GUIDANCE.
FORECAST CONSIDERATIONS LED TO STARTING WITH THE 00Z ECMWF/06Z
GFS/00Z CMC, IN ORDER FROM MORE TO LESS WEIGHT, FROM THURSDAY INTO
EARLY SATURDAY. THEN THE FORECAST QUICKLY MOVED TOWARD INCREASING
ENSEMBLE WEIGHT (MORE 00Z ECENS RELATIVE TO 06Z GEFS) AND
EVENTUALLY SOME WPC CONTINUITY. MEANS/CONTINUITY COMPRISED 80
PERCENT OF THE BLEND BY NEXT MONDAY.
..WEATHER/HAZARDS HIGHLIGHTS
MUCH COLDER THAN NORMAL TEMPERATURES WILL LINGER INTO THURSDAY
OVER PARTS OF THE EAST AND SOUTH. READINGS OF 15-25 DEGREES BELOW
NORMAL SHOULD NOT BE AS EXTREME AS PRIOR DAYS BUT A FEW DAILY
RECORD LOW MAX AND MIN TEMPERATURES ARE STILL POSSIBLE. EXPECT
TEMPERATURES TO CONTINUE MODERATING THEREAFTER, FINALLY REACHING
NEAR NORMAL THIS WEEKEND. THE COLD ANOMALIES SHOULD BE MOST
STUBBORN ALONG THE GULF COAST AND OVER THE FAR SOUTHEAST.
MEANWHILE, CALIFORNIA TO THE GREAT BASIN CAN EXPECT WARMER THAN
NORMAL TEMPERATURES THROUGH THE REST OF THE WORKWEEK BEFORE THE
WEST COOLS UNDERNEATH THE UPPER TROUGH NEXT WEEKEND. THE EASTERN
ROCKIES/HIGH PLAINS WILL ALSO SEE TEMPERATURES DROP BELOW NORMAL
(BY UP TO 15-20 DEGREES) THIS WEEKEND.
PRECIPITATION ACROSS THE LOWER 48 DURING THE MEDIUM RANGE PERIOD
SHOULD BE RELATIVELY QUIET. SOME RAIN IS POSSIBLE ACROSS FLORIDA ON
THURSDAY ASSOCIATED WITH A LINGERING FRONTAL BOUNDARY, WITH RAIN
OR LIGHT SNOW UP THE SOUTHEAST TO MID-ATLANTIC COAST WITH WEAK
FRONTAL WAVINESS OFFSHORE. A COUPLE COLD FRONTS/CLIPPER SYSTEMS MAY
PRODUCE SOME LIGHT/SCATTERED PRECIPITATION FROM THE NORTHERN
PLAINS TO MIDWEST/GREAT LAKES AND OHIO VALLEY, BUT SPECIFICS FOR
LOCATIONS SEEING MEASURABLE TOTALS WILL LIKELY WAIT UNTIL THE SHORT
RANGE TO BE RESOLVED. MORE WIDESPREAD RAIN AND MOUNTAIN SNOWS WILL
MOVE INTO THE WEST BY THURSDAY-FRIDAY AND SHIFT SOUTH WITH TIME,
LIKELY PROVIDING SOME MUCH NEEDED RAIN TO SOUTHERN CALIFORNIA NEXT
WEEKEND. THE TIGHT GRADIENT BEHIND A COLD FRONT DROPPING SOUTH
THROUGH THE WEST AND PLAINS MAY PRODUCE AN EPISODE OF STRONG WINDS
ALONG PARTS OF THE ROCKIES LATE THIS WEEK AND OVER CALIFORNIA AND
VICINITY BY SATURDAY. FARTHER EAST, SOME GULF MOISTURE WILL LIKELY
INTERACT WITH A FRONT APPROACHING/REACHING THE LOWER MISSISSIPPI
VALLEY TO TENNESSEE AND OHIO VALLEYS BY THIS COMING WEEKEND/EARLY
NEXT WEEK. LATEST GUIDANCE SHOWS POTENTIAL FOR SOME LOCALLY
ENHANCED RAINFALL OVER PARTS OF THE SOUTHERN TIER. SNOW WILL BE
POSSIBLE POSSIBLE FARTHER NORTH ACROSS THE GREAT LAKES, WITH A
WINTRY MIX POSSIBLE IN-BETWEEN DEPENDING ON CURRENTLY UNCERTAIN
UPPER LEVEL AND SURFACE DETAILS AT THAT TIME.
RAUSCH/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page