622
FXUS02 KWBC 310658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 AM EST TUE JAN 31 2023
VALID 12Z FRI FEB 03 2023 - 12Z TUE FEB 07 2023
...DANGEROUSLY COLD TEMPERATURES AND WIND CHILLS ARE FORECAST
ACROSS THE NORTH-CENTRAL U.S. LATE WEEK SPREADING INTO THE
NORTHEAST FOR THE WEEKEND...
..OVERVIEW
THE OVERALL UPPER-LEVEL PATTERN DURING THE MEDIUM RANGE PERIOD
LOOKS TO BE FAIRLY WAVY AND PROGRESSIVE, WITH NORTHERN STREAM
TROUGHING EXTENDING FROM A HUDSON BAY CLOSED LOW SHIFTING FROM THE
MIDWEST/GREAT LAKES INTO THE NORTHEAST LATE THIS WEEK AND
PRODUCING SIGNIFICANTLY COLD TEMPERATURES AND WIND CHILLS. RAIN
AND THUNDERSTORMS MAY LINGER INTO FRIDAY FOR THE FAR
SOUTHEAST/FLORIDA PENINSULA WITH A SOUTHERN STREAM WAVE.
MEANWHILE, A COUPLE OF ROUNDS OF UPPER TROUGHING COMING INTO THE
WEST WILL LEAD TO A WETTER PATTERN THERE, BUT NOTHING TOO EXTREME.
WHILE THE FIRST TROUGH MOVES ACROSS THE REST OF THE LOWER 48 THIS
WEEKEND WITH LITTLE IN THE WAY OF PRECIPITATION (ASIDE FROM
POSSIBLE GREAT LAKES SNOW) UNTIL IT REACHES THE EASTERN SEABOARD,
THE SECOND TROUGH IS MORE LIKELY TO PRODUCE PRECIPITATION ACROSS
THE CENTRAL U.S. BY AROUND NEXT MONDAY-TUESDAY, BUT WITH
UNCERTAINTY IN THE DETAILS AT THIS POINT.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATE THIS WEEK, MODEL GUIDANCE REMAINS IN REASONABLY GOOD
AGREEMENT WITH THE TRACK OF THE NORTHERN AND SOUTHERN STREAM
TROUGHS IN THE EASTERN U.S., WITH JUST MINOR DIFFERENCES IN THE
TIMING OF PHASING OF THOSE FEATURES. MEANWHILE MOST 12/18Z MODELS
REACHED A GENERAL CONSENSUS WITH THE AXIS POSITION AND THE DEPTH
OF THE TROUGHING COMING INTO THE WEST DAY 3/FRIDAY AND INTO THE
CENTRAL U.S. OVER THE WEEKEND. HOWEVER, THE 12Z CMC SEEMED TO BE A
DEEP AND SLOW EXCEPTION WHEN COMPARED TO OTHER DETERMINISTIC
MODELS AS WELL AS ENSEMBLE MEMBERS. THE CMC ALSO SHOWED MORE
STREAM SEPARATION, PUTTING MOST ENERGY IN THE SOUTHERN TIER.
MEANWHILE THE 12Z ECMWF INDICATED SOME STREAM SEPARATION, WHILE
GFS RUNS AND THE UKMET KEPT THE TROUGH PHASED. BY LATE SUNDAY INTO
MONDAY WHEN THE TROUGH REACHES THE EAST, THIS CREATES SOME NOTABLE
DIFFERENCES IN THE ECMWF WITH A FASTER NORTHERN STREAM TROUGH AND
LINGERING ENERGY IN THE GULF AS OPPOSED TO A PHASED TROUGH
STEADILY TRACKING EAST IN THE GFS RUNS. THE GFS RUNS ARE MORE
SIMILAR TO THE ENSEMBLE MEANS SO THEIR SOLUTION WAS FAVORED. THEN
WITH THE SECOND TROUGH DIGGING INTO THE WEST EARLY NEXT WEEK,
MODELS ARE IN AGREEMENT WITH THE EXISTENCE OF THIS FEATURE WITH
SOME TYPICAL VARIATIONS FOR THE LATTER MEDIUM RANGE TIMEFRAME. THE
ECMWF WAS PERHAPS AN OUTLIER WITH ADDITIONAL ENERGY DIGGING IN ON
THE WESTERN SIDE OF THE TROUGH BY MONDAY-TUESDAY, ELIMINATING THE
RIDGE ACROSS THE NORTHWEST THAT OTHER MODELS/ENSEMBLES SHOW.
GIVEN THE ABOVE CONSIDERATIONS, THE WPC FORECAST WAS BASED ON A
BLEND OF THE 12/18Z GFS AND 12Z ECMWF AND UKMET EARLY IN THE
PERIOD, INCREASING THE PROPORTION OF THE GEFS AND EC ENSEMBLE
MEANS AS THE PERIOD PROGRESSED AND LIMITING THE AMOUNT OF 12Z
ECMWF. GOOD CONTINUITY WAS MAINTAINED WITH THE PREVIOUS FORECAST,
AND THE INCOMING 00Z MODELS SEEM TO BE CONSISTENT AS WELL--THE 00Z
CMC ESPECIALLY SEEMED TO COME INTO BETTER ALIGNMENT WITH THE FIRST
COUPLE OF FEATURES, THOUGH SO FAR IT IS THE MOST AGGRESSIVE WITH
CLOSING OFF A LOW WITHIN THE SECOND TROUGH IN THE WEST.
..WEATHER/HAZARD HIGHLIGHTS
BY THE BEGINNING OF THE MEDIUM RANGE PERIOD FRIDAY, RAIN AND
THUNDERSTORMS MAY BE ONGOING ACROSS PORTIONS OF THE SOUTHEAST
BEFORE THE UPPER TROUGHING AND THE SURFACE LOW PRESSURE SYSTEM AND
FRONTAL BOUNDARY TRACK OFFSHORE. MOST AREAS ACROSS THE EAST WILL
BE DRY BY SATURDAY, BUT SOME MOISTURE RETURN BY SUNDAY COULD LEAD
TO PRECIPITATION ACROSS THE EASTERN SEABOARD, BUT WITH UNCERTAINTY
FOR HOW MUCH FALLS ONSHORE. FARTHER NORTH, LIGHT SNOW MAY EXPAND
IN COVERAGE ACROSS THE MIDWEST/GREAT LAKES/NORTHEAST BY THE
WEEKEND WITH A CLIPPER SYSTEM, ADDING TO SOME LIGHT LAKE EFFECT
AMOUNTS. MEANWHILE IN THE WEST, ROUNDS OF LIGHT TO MODERATE
PRECIPITATION CAN BE EXPECTED GIVEN THE COUPLE OF UPPER TROUGHS
MOVING THROUGH. THE PACIFIC NORTHWEST INTO NORTHERN CALIFORNIA
WILL BE THE MOST LIKELY TO SEE LOWER ELEVATION RAIN AND HIGHER
ELEVATION SNOW, WHILE THE NORTHERN ROCKIES AND OTHER AREAS OF THE
INTERMOUNTAIN WEST COULD SEE SOME LIGHT TO MODERATE SNOW AS WELL.
PRECIPITATION AMOUNTS WILL BE MORE TYPICAL OF NORMAL COOL SEASON
EVENTS AND NOTHING LIKE THOSE IN THE PARADE OF ATMOSPHERIC RIVER
EVENTS ABOUT A MONTH AGO. THEN THE SECOND UPPER TROUGH IN
PARTICULAR MAY PROVIDE SOME FORCING FOR PRECIPITATION TO DEVELOP
ACROSS THE CENTRAL U.S. BY MONDAY-TUESDAY, BUT THE SPECIFICS
REMAIN UNCERTAIN AT THIS POINT.
VERY COLD CONDITIONS ARE LIKELY FOR THE NORTH-CENTRAL TO
NORTHEASTERN TIER OF THE U.S. LATE THIS WEEK UNDERNEATH COLD UPPER
TROUGHING. ON FRIDAY HIGHS IN THE SINGLE DIGITS ARE FORECAST FOR
THE UPPER MIDWEST INTO NORTHERN NEW ENGLAND, AND BITTERLY COLD
LOWS COMBINED WITH WIND WILL PRODUCE DANGEROUS WIND CHILLS
ESPECIALLY SATURDAY MORNING. SEVERAL LOW MAXIMUM AND MINIMUM
TEMPERATURES COULD BE SET ESPECIALLY IN THE NORTHEAST BEFORE A
MODERATING TREND BY SUNDAY. BUT OTHER THAN THAT, TEMPERATURES ARE
EXPECTED TO TREND WARMER THAN AVERAGE ACROSS MOST AREAS, INCLUDING
THE CENTRAL U.S. AND SPREADING INTO THE EAST EARLY NEXT WEEK. THE
WEST COULD COOL DOWN ESPECIALLY IN TERMS OF HIGH TEMPERATURES
UNDERNEATH A LONGWAVE TROUGH BY MONDAY-TUESDAY THOUGH.
TATE
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES ARE
AT:
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
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