968
FXUS02 KWBC 130659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST MON JAN 13 2025
VALID 12Z THU JAN 16 2025 - 12Z MON JAN 20 2025
...STRONG ARCTIC SURGE PUSHING INTO THE CENTRAL U.S. BY THE WEEKEND
AND GRADUALLY EXPANDING EASTWARD...
..OVERVIEW
MODELS AND ENSEMBLES STILL SHOW THE MEAN PATTERN EVOLVING TOWARD A
VERY AMPLIFIED REGIME CONSISTING OF A RIDGE EXTENDING FROM THE
EASTERN PACIFIC WELL NORTHWARD AND A HUDSON BAY INTO NORTHERN
MEXICO MEAN TROUGH BY THE WEEKEND. AS A RESULT EXPECT VERY COLD
AIR TO DROP INTO THE CENTRAL U.S. THEN, WITH BELOW NORMAL
TEMPERATURES EXPANDING INTO THE EASTERN HALF OF THE COUNTRY BY NEXT
SUNDAY-MONDAY. ALTHOUGH THE LARGE SCALE PATTERN HAS WELL ABOVE
AVERAGE CONFIDENCE/PREDICTABILITY, THERE ARE EMBEDDED SHORTWAVE
DETAILS THAT GUIDANCE HAS BEEN SHOWING SIGNIFICANT DIFFICULTY IN
RESOLVING. AS A RESULT CONFIDENCE IS BELOW AVERAGE FOR ANY
ASSOCIATED SURFACE WAVES THAT COULD HAVE A SIGNIFICANT INFLUENCE ON
SENSIBLE WEATHER OVER THE EAST (WITH RAIN SOUTH AND POTENTIAL
WINTRY WEATHER FARTHER NORTH) FROM THE WEEKEND INTO EARLY NEXT
WEEK. THERE ARE ALSO UNCERTAINTIES WITH A LEADING SHORTWAVE
CROSSING THE SOUTHEASTERN QUADRANT OF THE LOWER 48 AROUND THURSDAY
AND A LOWER LATITUDE PACIFIC UPPER LOW WHOSE ENERGY SHOULD OPEN UP
AND EJECT ACROSS THE LOWER 48.
..GUIDANCE/PREDICTABILITY ASSESSMENT
EARLY IN THE PERIOD ON THURSDAY, THERE ARE STILL NOTABLE
DIFFERENCES WITH A SHORTWAVE FORECAST TO CROSS THE SOUTHEASTERN
QUADRANT OF THE COUNTRY. IN PARTICULAR, THE 00Z GFS IS A DEEP AND
SLOW EXTREME RELATIVE TO OTHER NEW GUIDANCE AND THIS RESULTS IN THE
MODEL RUN SPREADING MUCH MORE RAINFALL ACROSS FLORIDA. WHILE THE
MAJORITY OF GUIDANCE IS SIGNALING A WEAKER/FASTER SHORTWAVE WITH A
CORRESPONDING DRIER FORECAST OVER FLORIDA, THERE HAVE BEEN PREVIOUS
RANDOM SOLUTIONS WITH A GFS-LIKE SCENARIO. PREFERENCES SIDE WITH
THE MAJORITY SCENARIO BUT WITH THE UNDERSTANDING THAT A LOW-
PROBABILITY RISK STILL EXISTS FOR THE ALTERNATIVE.
ASIDE FROM THE GFS WHICH IS RECOVERING AFTER A COUPLE WEAK RUNS,
GUIDANCE HAS BEEN NUDGING A LITTLE STRONGER WITH THE SYSTEM
FORECAST TO TRACK NEAR NORTHERN MINNESOTA/LAKE SUPERIOR AROUND
FRIDAY AND CONTINUE INTO EASTERN CANADA THEREAFTER. AMPLIFYING
DYNAMICS WILL PUSH THE TRAILING COLD FRONT SOUTH AND EAST, WITH
NOTABLE SPREAD/CONTINUITY CHANGES FOR SHORTWAVE ENERGY FORECAST TO
DROP THROUGH THE WEST. THE 12Z AND NEW 00Z ECMWF RUNS HAVE BECOME
SOMEWHAT MORE PROGRESSIVE THAN A NUMBER OF ITS PRIOR RUNS (TRENDING
A LITTLE IN THE GFS/GEFS DIRECTION) WHILE THE CMC/CMCENS ARE
PERSISTENT IN SHOWING THE GREATEST AMPLITUDE/SHARPNESS OF WESTERN
ENERGY. EARLY ON SOME OF THESE DIFFERENCES INFLUENCE THE DETAILS OF
SHEARING PACIFIC UPPER LOW ENERGY (WITH SOME INFLUENCE ON SURFACE
WAVINESS/SOUTHERN TIER RAINFALL FARTHER EAST). THEN SHORTWAVE
DIFFERENCES HAVE A MORE SIGNIFICANT INFLUENCE ON POTENTIAL SURFACE
DEVELOPMENT TOWARD NEXT SUNDAY-MONDAY. LATEST ECMWF RUNS AND SOME
MACHINE LEARNING (ML) MODELS SHOW POTENTIAL FOR SOME COMBINATION OF
SHORTWAVE ENERGY TO SUPPORT A MID-ATLANTIC WAVE THAT TRACKS INTO OR
SOUTH OF THE CANADIAN MARITIMES. THE 18Z GFS FIT INTO THIS CLUSTER
AS WELL, BUT 12Z AND NEW 00Z RUNS SHOW A MORE INLAND SURFACE LOW
TRACK THAT SEEMS TO HAVE MINIMAL SUPPORT FROM OTHER GUIDANCE.
CMC/ICON RUNS SHOW A FLATTER EVOLUTION DUE TO HOLDING THE SHARPEST
UPPER TROUGHING FARTHER WEST. FINALLY, THERE IS A FAIR AMOUNT OF
SPREAD AMONG DYNAMICAL/ML MODELS FOR THE STRENGTH AND LOCATION OF
HIGH PRESSURE OVER THE CENTRAL U.S. BY NEXT MONDAY, WITH NO
DOMINANT CLUSTERING EVIDENT AT THIS TIME.
IN ORDER TO REFLECT A COMBINATION OF PREVAILING THEMES AND
ACCOUNTING FOR SPREAD/GUIDANCE VARIABILITY, THE UPDATED FORECAST
INCORPORATED PARTS OF THE 12Z AND 00Z/12 ECMWF RUNS, 18Z GFS, AND
SMALL INPUT FROM THE ENSEMBLE MEANS (18Z GEFS, 12Z CMCENS, AND
00Z/12 ECENS SINCE THE 12Z CYCLE WAS NOT AVAILABLE LOCALLY FOR
BLENDING).
..WEATHER/HAZARDS HIGHLIGHTS
AFTER A CHILLY START TO THURSDAY OVER PARTS OF THE EAST, EXPECT
TEMPERATURES TO MODERATE FROM LATE WEEK INTO THE WEEKEND AS ABOVE
NORMAL TEMPERATURES OVER THE PLAINS/MISSISSIPPI VALLEY ON
THURSDAY-FRIDAY (LOWS UP TO 15-25F ABOVE NORMAL OVER THE UPPER
MIDWEST) THEN REACH THE EAST WITH LESS PRONOUNCED ANOMALIES AHEAD
OF A COLD FRONT. BEHIND THE FRONT, EXPECT THE NORTHWEST TO SEE A
COOLING TREND ON FRIDAY, BUT THEN DURING THE WEEKEND THE EASTERN
ROCKIES INTO THE PLAINS WILL SEE A PRONOUNCED SURGE OF ARCTIC AIR.
EXPECT INCREASING COVERAGE OF TEMPERATURES THAT ARE 15-35F BELOW
NORMAL, WITH EXPANSION OF THE COLD AIR BRINGING HIGHS DOWN TO
10-20F BELOW NORMAL OVER THE EAST BY NEXT MONDAY. THE MOST EXTREME
ANOMALIES ARE LIKELY TO BE OVER THE CENTRAL HIGH PLAINS AND
VICINITY, WHILE COLDEST TEMPERATURES ON AN ABSOLUTE BASIS SHOULD BE
OVER FAR NORTHERN AREAS WHERE SOME SUBZERO HIGHS ARE POSSIBLE.
MUCH OF THE LOWER 48 SHOULD BE FAIRLY DRY ON THURSDAY. THE BEST
ORGANIZED ACTIVITY SHOULD BE ACROSS PARTS OF THE GREAT LAKES INTO
THE CENTRAL APPALACHIANS WITH PERIODS OF SNOW FROM A COMBINATION OF
LAKE EFFECT AND A WEAKENING FRONTAL SYSTEM PASSING THROUGH THE
REGION. BY FRIDAY OR FRIDAY NIGHT, APPROACHING SHORTWAVE ENERGY AND
A COMBINATION OF FRONTS MAY START TO GENERATE SOME ENHANCED
RAINFALL ACROSS THE SOUTHERN TIER. HOWEVER DIFFERENCES IN SHORTWAVE
DETAILS LEAD TO A FAIR AMOUNT OF SPREAD FOR LOCATION AND MAGNITUDE
OF AMOUNTS. THEREFORE THE DAY 5 EXCESSIVE RAINFALL OUTLOOK DOES NOT
REFLECT ANY RISK AREAS AT THIS TIME. POTENTIAL EXISTS FOR MUCH OF
THE EAST TO SEE AT LEAST SOME PRECIPITATION IN THE SATURDAY INTO
SUNDAY OR MONDAY PERIOD, BUT GUIDANCE DIFFERENCES FOR POTENTIAL
SURFACE DEVELOPMENT KEEP CONFIDENCE LOW FOR DETAILS OF
PRECIPITATION COVERAGE AND AMOUNTS. BEST POTENTIAL FOR WINTRY
WEATHER WILL BE FROM THE MID-ATLANTIC NORTHWARD, WITH RAIN FARTHER
SOUTH AND A POSSIBLE TRANSITION ZONE IN-BETWEEN. FARTHER WEST,
EXPECT SNOW TO MOVE SOUTHWARD ACROSS THE ROCKIES/HIGH PLAINS LATE
THIS WEEK INTO THE WEEKEND AS PART OF THE ARCTIC SURGE, WITH
UPSLOPE FLOW HELPING TO ENHANCED ACCUMULATIONS OVER SOME AREAS.
RAUSCH
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