185
FXUS02 KWBC 182035
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
335 PM EST WED JAN 18 2023
VALID 12Z SAT JAN 21 2023 - 12Z WED JAN 25 2023
...HEAVY SNOW THREAT FOR THE INTERIOR NORTHEAST SUNDAY INTO
MONDAY...
..OVERVIEW
GUIDANCE STILL MAINTAIN THE THEME OF A POSITIVELY TILTED MEAN
TROUGH OVER THE LOWER 48 WHILE A STRONG RIDGE PERSISTS OVER THE
EASTERN PACIFIC AND ANOTHER RIDGE PREVAILS SOUTHEAST OF FLORIDA.
EXPECT THIS PATTERN TO PRODUCE HIGHEST PRECIPITATION TOTALS OVER
THE SOUTHEAST AND VICINITY, BUT WITH MEANINGFUL TOTALS OF RAIN OR
SNOW ALSO POSSIBLY EXTENDING FARTHER WEST AND NORTH FROM THE
PLAINS INTO THE NORTHEAST WITH INDIVIDUAL EMBEDDED SYSTEMS.
LOCATIONS FROM THE NORTHWEST U.S. EAST/SOUTHEAST INTO THE ROCKIES
SHOULD SEE PERIODS OF RAIN AND MOUNTAIN SNOW WHILE MUCH OF THE
WEST REMAINS BELOW NORMAL FOR TEMPERATURES. THERE HAS BEEN
CONSIDERABLE GUIDANCE SPREAD AND VARIABILITY FOR THE SYSTEMS OF
INTEREST BUT LATEST RUNS ARE STARTING TO SHOW BETTER CLUSTERING IN
SOME RESPECTS, PROVIDING HOPE FOR IMPROVED CONFIDENCE SOMETIME
SOON FOR SENSIBLE WEATHER DETAILS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT FORECAST UNCERTAINTY HAS REVOLVED AROUND TWO PRIMARY
FEATURES, A LEADING UPPER LOW EMERGING FROM THE SOUTHERN ROCKIES
EARLY SATURDAY (WITH QUESTIONS OVER INTERACTION WITH SOUTHERN
CANADA/NORTHERN PLAINS ENERGY TO THE NORTH) AND TRAILING SHORTWAVE
ENERGY DROPPING INTO THE WEST DURING THE WEEKEND INTO EARLY NEXT
WEEK. RECENT GUIDANCE HAS INCREASINGLY AGREE TO THE NOTION THAT
LOW PRESSURE WILL TRACK WEST OF THE APPALACHIANS BY SUNDAY AND
THEN DEEPEN INTO A FAIRLY STRONG LOW PRESSURE SYSTEM OVER NEW
ENGLAND BY EARLY MONDAY. THE ECMWF/GFS AND THEIR ENSEMBLE MEAN
SOLUTIONS ARE REASONABLY WELL CLUSTERED, WHILE RECENT CMC AND
UKMET TEND TO OFFER A FARTHER SOUTHEAST TRACK OFF THE COAST. A
FAVORED COMPOSITE OF THE LATEST GFS/ECMWF AND ENSEMBLE MEANS
MAINTAINS GOOD WPC PRODUCT CONTINUITY WITH DEPICTION OF A STORMY
LOW TO AFFECT THE NORTHEAST FOR MULTIPLE DAYS WITH A THREAT FOR
ENHANCED WINDS AND WRAPPING PRECIPITATION TO INCLUDE A THREAT FOR
HEAVY SNOW ICE FOR MAINLY INTERIOR AREAS.
HOWEVER, FORECAST SPREAD MEANWHILE CONTINUES TO NOT BE STELLAR
WITH RESPECT TO THE UPSTREAM FLOW OF ENERGY/SYSTEMS DIGGING INTO
THE WEST AND SUBSEQUENT EJECTION DOWNSTREAM INTO THE CENTRAL AND
EASTERN U.S. INTO NEXT WEEK. THE 06 UTC GFS SEEMS AN OUTLIER RUN
THAT SHOWED MUCH LESS DIGGING OF MAIN ENERGIES INTO THE WEST
COMPARED TO OTHER GUIDANCE INCLUDING THE 00 UTC GFS AND ENSEMBLES.
THE PATTERN SEEMS TO FAVOR AT LEAST DECENT DIGGING TO THE LEE OF
AN AMPLIFIED UPSTREAM UPPER RIDGE. THE 12 UTC GFS HAS AT LEAST
TRENDED MORE AMPLIFIED AND ALTERNATE GUIDANCE STILL OFFER
AMPLIFIED SOLUTIONS. THE 12 UTC ECMWF HAS ALSO SEEMINGLY FAVORABLY
TRENDED LESS PROGRESSIVE THAN AN OUTLIER FASTER 00 UTC RUN WITH
MAIN SYSTEM EJECTION OUT FROM THE WEST INTO THE CENTRAL/EASTERN
U.S. NEXT WEEK. OVERALL, THOUGHT THE 00 UTC ECMWF ENSEMBLE MEAN
KEPT THINGS ON THE BEST TRACK CONTINUITY WISE DOWNSTREAM FROM THE
WEST INTO THE CENTRAL AND EASTERN U.S. INTO NEXT WEEK, ALBEIT WITH
MORE UNCERTAINTY THAN NORMAL.
ACCORDINGLY OVERALL, THE WPC MEDIUM RANGE PRODUCT SUITE WAS
PRIMARILY DERIVED FROM A COMPOSITE BLEND OF THE 00 UTC GFS/ECMWF
AND GEFS/ECMWF ENSEMBLE MEANS FOR THIS WEEKEND BEFORE QUICKLY
SWITCHING TO THE 00 UTC ECMWF ENSEMBLE MEAN INTO NEXT WEEK. THE
ECMWF ENSEMBLE MEAN SEEMS TO OFFER STREAM FLOW AMPLITUDE AND
TIMING THAT SEEMS THE BEST CONTINUITY ALONG WITH INTERMEDIATE
TIMINGS OF EMBEDDED MAIN SYSTEMS IN A PERIOD OF QUICKLY INCREASING
FORECAST SPREAD AND UNCERTAINTY INTO THESE LONGER TIME FRAMES.
..WEATHER/HAZARD HIGHLIGHTS
WHILE THERE IS STILL A FAIR AMOUNT OF UNCERTAINTY IN FORECAST
SPECIFICS, THERE CONTINUES TO BE SOME IMPROVEMENT IN THE BROAD
THEME OF TWO PRIMARY SYSTEMS AND THEIR GENERAL TIMING. THE FIRST
SHOULD TRACK FROM THE PLAINS THROUGH THE CENTRAL/NORTHERN EAST
COAST SATURDAY-MONDAY, BRINGING THE POTENTIAL FOR WINTRY WEATHER
FROM THE CENTRAL PLAINS INTO ESPECIALLY THE APPALACHIANS/INTERIOR
NORTHEAST, WITH RAIN TO THE SOUTH. EXPECT THE HEAVIEST RAIN OVER
THE SOUTHEAST WHERE GULF MOISTURE MAY INTERACT WITH A LEADING WARM
FRONT. MOST GUIDANCE HAS BEEN TRENDING DEEPER FOR THIS STORM NEAR
NEW ENGLAND BY MONDAY, SO BRISK TO STRONG WINDS COULD BE POSSIBLE.
THERE IS STILL POTENTIAL FOR A MEANINGFUL CHANGE IN THE MOST
LIKELY TRACK SO CONTINUE TO MONITOR FORECASTS FOR THIS SYSTEM.
THE NEXT SYSTEM MAY AFFECT THE CENTRAL-EASTERN U.S. BY
TUESDAY-WEDNESDAY WITH A PRECIPITATION DISTRIBUTION THAT COULD
HAVE SOME SIMILARITIES TO THE FIRST SYSTEM. HOWEVER THERE ARE
SIGNALS THAT THIS LATTER SYSTEM COULD BE DEEPER THAN THE LEAD
STORM WHILE STILL WEST OF THE APPALACHIANS. ACROSS THE WEST, RAIN
AND MOUNTAIN SNOW OF MOSTLY MODERATE AMOUNTS SHOULD EXTEND FROM
THE NORTHWEST THROUGH THE NORTHERN AND CENTRAL ROCKIES WITH UPPER
TROUGH/LOW SUPPORT AND LOWER LEVEL UPSLOPE FLOW. SOUTHWESTWARD
EXTENT OF THE PRECIPITATION WILL DEPEND ON EXACT TRACK/AMPLITUDE
OF THE WEEKEND FEATURE WHOSE DETAILS REMAIN UNRESOLVED.
MOST ASPECTS OF THE TEMPERATURE FORECAST HAVE CHANGED LITTLE OVER
THE PAST DAY. THE NORTHERN THREE-FOURTHS OF THE WEST AND INTO
PARTS OF THE HIGH PLAINS STILL LOOK CHILLY THROUGH THE PERIOD WITH
HIGHS 5-20F BELOW NORMAL. AN ISOLATED LOCATION OR TWO COULD SEE A
RECORD COLD HIGH. LOCATIONS ACROSS THE EASTERN U.S. AND NORTHERN
PLAINS SHOULD SEE NEAR TO ABOVE NORMAL HIGHS WITH GENERALLY WARMER
ANOMALIES (UP TO PLUS 10-20F OVER SOME AREAS) FOR LOWS.
RAUSCH/SCHICHTEL
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE INTERIOR NORTHEAST,
AND INTERIOR NEW ENGLAND, SUN-MON,
JAN 22-JAN 23.
- HEAVY RAIN ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, THE
TENNESSEE VALLEY, AND THE
SOUTHEAST, SAT-SUN, JAN 21-JAN 22.
- HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN CASCADES, AND CENTRAL
IDAHO, SAT, JAN 21.
- HEAVY SNOW ACROSS PORTIONS OF NORTHERN UPSTATE NEW YORK, AND
NORTHERN NEW ENGLAND, SUN-MON, JAN
22-JAN 23.
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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