705
FXUS02 KWBC 190700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 AM EST THU JAN 19 2023
VALID 12Z SUN JAN 22 2023 - 12Z THU JAN 26 2023
...HEAVY SNOW THREAT FOR THE INTERIOR NORTHEAST SUNDAY INTO
MONDAY...
..OVERVIEW
THE ESTABLISHED MEAN PATTERN EXTENDING INTO NEXT WEEK WILL FEATURE
A STRONG EASTERN PACIFIC RIDGE AND A SEQUENCE OF SHORTWAVES
DROPPING INTO THE WEST THEN EJECTING BEYOND THE ROCKIES TO PRODUCE
INDIVIDUAL SYSTEMS GENERATING VARIOUS TYPES OF SIGNIFICANT
WEATHER. THESE SHORTWAVES/SYSTEMS WILL LIKELY PRODUCE SOME
LOCALLY FOCUSED RAIN/MOUNTAIN SNOW FROM THE NORTHWEST EAST AND
SOUTHEAST INTO THE ROCKIES, AND THEN HEAVIEST RAINFALL POTENTIAL
OVER THE SOUTHEAST AND WINTER WEATHER POTENTIAL FROM THE PLAINS
INTO THE NORTHEAST, WITH MORE MODERATE RAINFALL TOTALS BETWEEN
THESE TWO AREAS. CONFIDENCE IS STEADILY INCREASING FOR THE
LEADING SYSTEM FORECAST TO REACH NEW ENGLAND BY EARLY MONDAY GIVEN
IMPROVEMENT IN GUIDANCE CLUSTERING. HOWEVER THERE ARE STILL
IMPORTANT DIFFERENCES FOR THE ENERGY DROPPING INTO THE WEST
SUNDAY-MONDAY, ULTIMATELY CAUSING CONTINUED FORECAST CHALLENGES
FOR PRECIPITATION SPECIFICS OVER THE WEST AND THE SYSTEM THAT MAY
AFFECT THE CENTRAL-EASTERN U.S. ABOUT THREE DAYS AFTER THE FIRST
ONE. GUIDANCE SUGGESTS THAT SUBSEQUENT ENERGY DROPPING INTO THE
WEST WILL BE A LOT WEAKER, YIELDING A BROADER MEAN TROUGH BY NEXT
THURSDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOR THE LEADING SYSTEM REACHING NEW ENGLAND BY MONDAY, FOLLOWING A
MAJORITY MODEL/ENSEMBLE CLUSTER HAS HELD UP WELL CONTINUITY-WISE
OVER THE PAST DAY OR SO SINCE GUIDANCE FULLY ADJUSTED TO THE
CURRENTLY DEPICTED PHASING ALOFT OVER THE CENTRAL U.S. DURING THE
WEEKEND. LATEST UKMET/CMC RUNS HAVE ADJUSTED CLOSER TO THE
MAJORITY SCENARIO FOR THE SURFACE LOW TRACK AFTER SOME EARLIER
RUNS WERE ON THE SOUTH/SOUTHEAST SIDE OF THE SPREAD PREVIOUSLY.
THE 00Z CMC DOES STRAY A BIT ON THE SLOW SIDE BY LATE MONDAY
THOUGH, AS MOST GUIDANCE SHOWS A FAIRLY STRONG SYSTEM REACHING
NEAR NOVA SCOTIA AT THAT TIME. OVERALL AN OPERATIONAL MODEL
COMPOSITE WITH GREATER EMPHASIS ON THE 12Z GFS/ECMWF PROVIDED A
REASONABLE STARTING POINT.
MODELS/ENSEMBLES HAVE BEEN DIVERSE AND INCONSISTENT FOR DAYS WITH
THE TRAILING SHORTWAVE DIGGING INTO THE WEST, HIGHLIGHTED BY
PRONOUNCED REVERSALS IN THE ECMWF AND GFS RUNS OVER THE PAST DAY
OR SO. AS OF NOW THE GFS IS ON THE OPEN AND PROGRESSIVE SIDE OF
THE SPREAD THROUGH MONDAY, IN CONTRAST TO A COUPLE DAYS AGO WHEN
IT WAS A DEEP/SOUTHWESTERN EXTREME WITH ITS UPPER LOW. ON THE
OTHER HAND THE ECMWF HAS MADE THE OPPOSITE ADJUSTMENT FROM BEING
PROGRESSIVE TO JOINING A SLOWER CLUSTER THAT IS NOW CLOSE TO THE
UKMET/CMC. THESE DIFFERENCES LEAD TO CORRESPONDING TIMING AND
EVOLUTION DIFFERENCES ACROSS THE CENTRAL-EASTERN U.S. THROUGH
THURSDAY. THE 12Z/18 GFS WAS SOMEWHAT CLOSER TO OTHER GUIDANCE
(VERSUS THE FASTER 18Z RUN, AND NOW THE 00Z RUN) SO PREFERRED THAT
RUN FOR WHAT GFS INPUT WAS INCLUDED IN THE FORECAST BLEND. EVEN
WITH SOME OF THE DIFFERENCES ALONG THE WAY, THE 12Z ECENS/CMCENS
AND 18Z GEFS MEANS ALONG WITH THE 12Z GFS/ECMWF/CMC ENDED UP WITH
REMARKABLY SIMILAR SURFACE LOW POSITIONS NEAR NEW ENGLAND BY EARLY
DAY 7 THURSDAY. INCLUDING COMPONENTS OF THOSE THREE OPERATIONAL
MODELS HELPED TO ADD SOME DEFINITION RELATIVE TO THE ENSEMBLE
MEANS ALONG WITH INTERMEDIATE TIMING. THE RESULTING BLEND
PROVIDED REASONABLE CONTINUITY FOR THE UPPER SYSTEM AND SURFACE
REFLECTION THROUGH THE PERIOD.
..WEATHER/HAZARD HIGHLIGHTS
THE FORECAST REMAINS ON TRACK WITH THE GENERAL THEME OF TWO
SIGNIFICANT SYSTEMS AFFECTING THE EASTERN HALF OF THE COUNTRY
DURING THE PERIOD, WITH GREATER CONFIDENCE FOR DETAILS OF THE
FIRST ONE THAN THE SECOND. THE FIRST SYSTEM WILL LIKELY TRACK
FROM THE MISSISSIPPI VALLEY/GULF COAST INTO NEW ENGLAND
SUNDAY-MONDAY, BRINGING THE POTENTIAL FOR SOME WINTRY WEATHER FROM
THE MIDWEST INTO THE CENTRAL-NORTHERN APPALACHIANS AND INTERIOR
NEW ENGLAND. THE APPALACHIANS/NEW ENGLAND AREA HAS THE BEST
POTENTIAL FOR MEANINGFUL TO HEAVY SNOW TOTALS. EXPECT RAIN TO THE
SOUTH OF THE SNOW AREA, WITH HEAVIEST RAINFALL MOST LIKELY OVER
THE SOUTHEAST. CURRENTLY EXPECT THE NEXT SYSTEM TO DEVELOP OVER
THE SOUTHERN PLAINS/GULF COAST AROUND TUESDAY AND THEN REACH NEAR
NEW ENGLAND BY THURSDAY, BUT SOME CHANGES ARE POSSIBLE IN THE
DETAILS. DEPENDING ON EXACTLY HOW THIS SYSTEM EVOLVES, THERE MAY
BE SIMILARITIES IN PRECIPITATION DISTRIBUTION/AMOUNTS, INCLUDING
THE BEST HEAVY RAINFALL POTENTIAL OVER THE SOUTHEAST AND A BAND OF
WINTRY WEATHER FROM THE PLAINS NORTHEASTWARD INTO NEW ENGLAND.
THE EXACT RAIN-SNOW LINE WILL DEPEND ON FINER DETAILS OF SYSTEM
STRENGTH/TRACK THAT ARE STILL NOT RESOLVED WELL. BOTH OF THESE
SYSTEMS MAY BE STRONG ENOUGH TO PRODUCE ENHANCED WINDS OVER THE
NORTHEAST. ACROSS THE WEST, RAIN AND MOUNTAIN SNOW OF MOSTLY
MODERATE AMOUNTS (BUT PERHAPS LOCALLY ENHANCED) SHOULD EXTEND
SOUTH-SOUTHEAST ACROSS THE ROCKIES AND NEARBY AREAS WITH UPPER
TROUGH/LOW SUPPORT AND LOWER LEVEL UPSLOPE FLOW. SOUTHWESTWARD
EXTENT OF THE PRECIPITATION WILL DEPEND ON EXACT TRACK/AMPLITUDE
OF THE WEEKEND/EARLY NEXT WEEK FEATURE WHOSE DETAILS REMAIN
UNCERTAIN.
MOST AREAS FROM THE NORTHERN THREE-FOURTHS OF THE WEST INTO THE
CENTRAL-SOUTHERN HIGH PLAINS SHOULD REMAIN CHILLY THROUGH THE
PERIOD WITH HIGHS GENERALLY 5-15F BELOW NORMAL BUT POSSIBLY UP TO
SEVERAL DEGREES COLDER AROUND MONDAY UNDERNEATH OR IN THE WAKE OF
AN UPPER TROUGH/LOW OVER THE FOUR CORNERS STATES. FAR NORTHERN
PARTS OF THE WEST SHOULD BE WITHIN A FEW DEGREES ON EITHER SIDE OF
NORMAL, WHILE HIGHS AT LOCATIONS ALONG THE CENTRAL-NORTHERN WEST
COAST MAY DRIFT A FEW DEGREES ABOVE NORMAL AS THE EASTERN PACIFIC
UPPER RIDGE EXTENDS A TAD EASTWARD. MEANWHILE THE EASTERN U.S.
WILL TEND TO SEE ABOVE NORMAL LOWS, OCCASIONALLY BY MORE THAN 10F,
WHILE HIGHS SHOULD BE NEAR TO MODERATELY ABOVE NORMAL. THE
NORTHERN PLAINS AND VICINITY WILL TEND TO BE ABOVE NORMAL INTO
MIDWEEK AND THEN TREND COLDER BY THURSDAY AFTER PASSAGE OF A COLD
FRONT DROPPING SOUTH FROM CANADA.
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, 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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