408
FXUS02 KWBC 191840
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
138 PM EST THU JAN 19 2023
VALID 12Z SUN JAN 22 2023 - 12Z THU JAN 26 2023
...TWO DEEP LOWS WITH A HEAVY SNOW THREAT FOCUS FOR THE
APPALACHIANS/INTERIOR NORTHEAST SUNDAY/MONDAY AND BY WEDNESDAY...
..OVERVIEW
IT REMAINS THE CASE THAT AN ESTABLISHED PATTERN 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 A
LEAD SYSTEM FORECAST TO REACH THE NORTHEAST SUNDAY-MONDAY GIVEN
IMPROVEMENT IN GUIDANCE CLUSTERING. THERE ARE STILL 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 ON THE HEELS OF THE LEAD ONE. HOWEVER,
FORECAST SPREAD IS STEADILY IMPROVING WITH LATEST GUIDANCE,
BOLSTERING FORECAST CONFIDENCE IN DEVELOPMENT AND TRACK. GUIDANCE
SUGGESTS THAT SUBSEQUENT ENERGY DROPPING INTO THE WEST WILL BE A
LOT WEAKER INTO LATER NEXT WEEK, YIELDING A BROADER MEAN TROUGH
ALOFT, BUT THERE IS ROOM FOR ADDITIONAL DIGGING.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOR THE LEADING SYSTEM REACHING THE NORTHEAST SUNDAY-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. RECENT 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. OVERALL AN OPERATIONAL MODEL COMPOSITE WITH GREATER
EMPHASIS ON THE LATEST GFS/ECMWF PROVIDE 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. THE LATEST FEW RUNS OF THE ECMWF/CANADIAN/UKMET HAVE
SLOWLY CONVERGED UPON A BETTER CLUSTER FORECAST EVOLUTION. RECENT
GFS AND TO A LESSER EXTENT GEFS RUNS HAVE BEEN ON THE OPEN AND
PROGRESSIVE SIDE OF THE SPREAD THROUGH MONDAY, BUT THE LATEST 12
UTC VERSION HAS FINALLY TRENDED A BIT SLOWER AT LEAST TOWARD THE
REST OF MODEL GUIDANCE, BOLSTERING FORECAST CONFIDENCE ACROSS THE
REGION AND ALSO WITH CORRESPONDING THE EVOLUTION OF DOWNSTREAM
SYSTEM DEVELOPMENT AND THREATS ACROSS THE CENTRAL-EASTERN U.S.
THROUGH NEXT THURSDAY. EVEN WITH SOME LINGERING DIFFERENCES ALONG
THE WAY, STORM DEVELOPENT AND IMPACT NOW HAS A GOOD GUIDANCE
SIGNAL. RECENT GEFS/ECENS/CMCENS MEANS ALONG WITH THE
GFS/ECMWF/CMC FOUND A WAY TO SHOW REMARKABLY SIMILAR/DEEPENED
SURFACE LOW POSITIONS NEAR NEW ENGLAND BY EARLY DAY 7 THURSDAY AND
A BLEND PROVIDES GOOD CONTINUITY FOR THE UPPER SYSTEM AND SURFACE
REFLECTION THROUGH THE PERIOD.
..WEATHER/HAZARD HIGHLIGHTS
TWO SIGNIFICANT SYSTEMS WILL WORK OUT FROM THE WEST TO TRAVERSE
THE SOUTH-CENTRAL U.S. AND THEN IMPACT THE EASTERN HALF OF THE
COUNTRY DURING THIS PERIOD. 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/SCHICHTEL
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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