999
FXUS02 KWBC 041900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST THU JAN 04 2024
VALID 12Z SUN JAN 07 2024 - 12Z THU JAN 11 2024
...MAJOR WINTER STORM TO CONTINUE BRINGING HAZARDOUS WEATHER
ACROSS PARTS OF THE NORTHEAST INTO SUNDAY...
...ANOTHER MAJOR STORM TO BRING HEAVY RAIN/STRONG CONVECTION AND
GUSTY WINDS ACROSS THE SOUTH-CENTRAL U.S. AND INTO THE EAST EARLY
TO MIDDLE OF NEXT WEEK, WITH A HEAVY SNOW THREAT TO THE NORTH...
...DYNAMIC STORM SYSTEMS TO FOCUS COASTAL RAIN/INLAND HEAVY SNOW
THREATS OVER THE NORTHWEST/WEST NEXT WEEK...
..OVERVIEW
AN EXTREMELY ACTIVE MEDIUM RANGE PERIOD REMAINS ON TAP WITH A
SERIES OF MAJOR STORM SYSTEMS IN THE FORECAST. A LEADING SYSTEM
WILL BE EXITING THE EAST ON SUNDAY, WITH SOME POTENTIAL FOR
LINGERING HAZARDOUS WEATHER ACROSS PARTS OF THE NORTHEAST. IN ITS
WAKE, ANOTHER MAJOR UPPER TROUGH WILL BE DIGGING THROUGH A HIGHLY
UNSETTLED WEST THIS WEEKEND AS WELL, FOCUSING WINTRY THREATS FOR
TERRAIN/MOUNTAIN SNOWS AND WINDS. DEEP CYCLOGENESIS THEN REMAINS
LIKELY ACROSS THE SOUTH-CENTRAL PLAINS BY MONDAY, WITH IMPRESSIVE
LEAD MOISTURE AND INSTABILITY RETURNING TO FUEL WIDESPREAD HEAVY
RAINFALL/CONVECTION AND RUNOFF ISSUES ACROSS THE SOUTH-CENTRAL TO
EASTERN U.S. THROUGH THE MIDDLE OF NEXT WEEK. TO THE NORTH OF THE
DEEP LOW'S TRACK, THERE IS ALSO A SIGNIFICANT SNOW/ICE THREAT FROM
THE CENTRAL PLAINS TO THE MIDWEST/GREAT LAKES AND NORTHEAST
MONDAY-WEDNESDAY, ALONG WITH STRONG AND GUSTY WINDS. ADDITIONAL
DYNAMIC SYSTEMS IN THE SERIES LOOK TO MOVE INTO THE PACIFIC
NORTHWEST EARLY NEXT WEEK BEFORE DIGGING ACROSS THE WEST INTO
MID-LATE NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE CONTINUES TO SUGGEST BETTER THAN AVERAGE
CONFIDENCE FOR SIGNIFICANT LARGE SCALE FEATURES IN A VERY ACTIVE
JANUARY STORM PATTERN ACROSS MUCH OF THE NATION FOR AT LEAST THE
NEXT WEEK. THERE ARE SOME DETAIL DIFFERENCES FOR LEADING SYSTEMS
AFFECTING THE EASTERN HALF OF THE COUNTRY WHILE THE LATTER PART OF
THE PERIOD FEATURES TYPICALLY INCREASING SPREAD FOR SOME SPECIFICS
WITHIN THE UPPER TROUGH AMPLIFYING OVER THE WESTERN U.S. AND
NORTHERN PLAINS.
FOR THE SYSTEM EXPECTED TO BE JUST SOUTH OF NEW ENGLAND AS OF
EARLY SUNDAY, THE PRIMARY DIFFERENCE AT THE MOMENT IS THAT THE NEW
12Z GFS IS ON THE SOUTHWESTERN SIDE OF THE GUIDANCE SPREAD (WITH A
CORRESPONDING SHIFT IN THE AXIS OF HEAVIEST NEW ENGLAND SNOWFALL).
PRIOR GFS RUNS WERE LESS EXTREME IN THAT REGARD.
THEN THE PRIMARY FOCUS DURING THE PERIOD WILL BE ON THE STORM
LIKELY TO DEVELOP AND IMPACT MUCH OF EASTERN HALF OF THE COUNTRY
NEXT WEEK. MODELS AGREE ON A DEEPENING UPPER TROUGH ACROSS THE
WEST SUNDAY, WITH 00Z/06Z GUIDANCE CLUSTERING FAIRLY WELL FOR THE
OVERALL TRACK AND TIMING AS THE SYSTEM KICKS OUT INTO THE PLAINS
AND TRACKS THROUGH THE EASTERN GREAT LAKES BY WEDNESDAY. THE NEW
12Z CMC HAS STRAYED FROM ESTABLISHED CONSENSUS AND ITS 00Z RUN IN
SHOWING A FARTHER SOUTH TRACK OF THE UPPER LOW/SURFACE SYSTEM.
THE STRENGTH OF THIS SYSTEM WILL BE ANOTHER FORECAST
CONSIDERATION. ESPECIALLY BY EARLY WEDNESDAY THE 00Z ECMWF SHOWS
A DEEPER SURFACE LOW THAN OTHER GUIDANCE OR ITS PREVIOUS RUNS WITH
A CENTRAL PRESSURE IN THE MID 960S MB (TEMPERED A BIT IN THE NEW
12Z RUN) WHILE IN CONTRAST LATEST GFS RUNS ARE SOMEWHAT ON THE
WEAKER SIDE OF THE SPREAD IN THE LOW 980S. MOST OF THE 00Z
ECMWF-INITIALIZED MACHINE LEARNING MODELS FAVOR A DEPTH CLOSE TO
975 MB AND THE UKMET/CMC ARE SIMILAR. THUS FOR NOW WILL DEPICT A
CENTRAL PRESSURE JUST UNDER 976 MB AS OF EARLY WEDNESDAY.
VERIFICATION ON THE DEEPER SIDE OF THE GUIDANCE SPREAD COULD
CHALLENGE JANUARY SEA LEVEL PRESSURE RECORDS WITHIN AN AREA FROM
THE SOUTH-CENTRAL MISSISSIPPI VALLEY INTO LOWER OHIO VALLEY.
RECORDS OVER AREAS FARTHER EAST IN THE OHIO VALLEY/GREAT LAKES ARE
FROM THE HISTORIC LATE JANUARY STORM OF 1978 AND APPEAR MUCH MORE
DIFFICULT TO REACH.
BEHIND THIS SYSTEM, THERE IS REASONABLE CONSENSUS FOR A FRONTAL
SYSTEM TO REACH THE PACIFIC NORTHWEST AROUND MONDAY. THE
DEVELOPING MEDIUM-SMALLER SCALE SHORTWAVE DIFFERENCES LEAD TO SOME
SPREAD FOR AN IMMEDIATELY TRAILING SYSTEM, WITH THIS ENERGY AND
PERHAPS UPSTREAM FLOW FROM WESTERN CANADA DIFFERING
WEDNESDAY-THURSDAY WITHIN A MORE AGREEABLE LARGE SCALE WESTERN
TROUGH. THE 12Z GFS HAS CHANGED SOME DETAILS FROM ITS 00Z/06Z
RUNS WHILE THE 12Z CMC HAS STRAYED THE MOST FROM THE OVERALL
MODEL/ENSEMBLE MAJORITY, BECOMING QUITE FAST WITH INCOMING PACIFIC
NORTHWEST ENERGY. BY NEXT THURSDAY THERE IS A GOOD SIGNAL FOR LOW
PRESSURE TO REACH THE PLAINS BUT SPECIFICS WILL BE SENSITIVE TO
SHORTWAVE DETAILS THAT MAY TAKE A WHILE TO RESOLVE, WHILE A STRONG
COLD FRONT SHOULD DIP INTO THE FAR NORTHERN TIER.
A 00Z/06Z MODEL COMPOSITE PROVIDED A GOOD START FOR THE UPDATED
FORECAST THROUGH THE FIRST HALF OF THE PERIOD, REFLECTING
CONSENSUS AND/OR THE PREFERRED INTERMEDIATE SOLUTION. EVEN BY
DAYS 6-7 WEDNESDAY-THURSDAY A BLEND OF THE GFS/ECMWF/CMC ALREADY
TONED DOWN SOME LESS CONFIDENT ASPECTS OF ANY PARTICULAR SOLUTION
WITH GENERAL SUPPORT FROM THE ENSEMBLE MEANS, REQUIRING ONLY
MODERATE INCORPORATION OF 06Z GEFS/00Z ECENS.
..WEATHER/HAZARDS HIGHLIGHTS
THE MAJOR SURFACE LOW BRINGING SNOW AND ICE TO PARTS OF THE
MID-ATLANTIC/NORTHEAST WILL BE EXITING THE EAST COAST BY SUNDAY,
BUT THERE COULD STILL BE SOME HAZARDOUS WEATHER ACROSS PARTS OF
NEW ENGLAND, INCLUDING MODERATE TO HEAVY SNOWS AND GUSTY WINDS.
CURRENTLY EXPECT THE BEST POTENTIAL FOR MEANINGFUL SNOW ON SUNDAY
TO BE OVER EASTERN PORTIONS OF NEW ENGLAND.
THE NEXT SYSTEM AFFECTING THE WEST WILL BRING SOME RAIN AND
MOUNTAIN SNOWS ACROSS THE FOUR CORNERS REGION ON SUNDAY WITH A
DECENT SIGNAL FOR MEANINGFUL SNOW ACCUMULATIONS ACROSS PARTS OF
THE SOUTHERN ROCKIES. AS THE PARENT TROUGH AND EMBEDDED CLOSED
LOW EJECT INTO THE PLAINS, AN AREA OF LOW PRESSURE WILL DEEPEN AS
IT TRACKS NORTHEASTWARD INTO THE MISSISSIPPI VALLEY AND EASTERN
GREAT LAKES NEXT WEEK. THIS SYSTEM WILL TAP GULF OF MEXICO
MOISTURE TO FUEL WIDESPREAD MODERATE TO HEAVY RAINFALL ACROSS MUCH
OF THE MID/LOWER MISSISSIPPI VALLEY AND THE SOUTH ON MONDAY WITH
SOME SEVERE WEATHER POTENTIAL AS WELL ALONG THE CENTRAL GULF
COAST, PER THE LATEST OUTLOOK FROM THE STORM PREDICTION CENTER.
GIVEN AMPLE MOISTURE AND INSTABILITY, AND WET GROUND CONDITIONS
DUE TO RAINFALL EXPECTED IN THE SHORT RANGE PERIOD, THE DAY 5
EXCESSIVE RAINFALL OUTLOOK DEPICTS A SLIGHT RISK AREA ACROSS THE
CENTRAL/EAST-CENTRAL GULF COAST REGION--EXPANDED SOMEWHAT RELATIVE
TO PRIOR ISSUANCE BASED ON THE BEST CONSENSUS OF LATEST
MODEL/ENSEMBLE SIGNALS. A BROAD MARGINAL RISK AREA COVERS THE
SOUTH AND EXTENDS FARTHER NORTHWARD INTO THE MISSISSIPPI VALLEY
WHERE THERE COULD BE A SECONDARY MAXIMUM CLOSER TO THE LOW TRACK.
ON TUESDAY RAIN WILL MOVE INTO THE EASTERN U.S. AND DEPENDING ON
SNOW ACCUMULATIONS ACROSS PARTS OF THE EAST THIS WEEKEND, THIS
COULD BRING AN INCREASED RISK FOR FLOODING DUE TO EXCESSIVE RAIN
AND SNOWMELT. MEANWHILE SEVERE WEATHER POTENTIAL MAY CONTINUE
EASTWARD INTO THE FAR SOUTHEAST/FLORIDA. EXPECT AT LEAST A COUPLE
DAYS OF STRONG AND GUSTY WINDS AROUND THE DEEP LOW ACROSS THE
EAST-CENTRAL U.S. TO NORTHEASTERN U.S. AS THIS SYSTEM STRENGTHENS.
THERE IS ALSO AN INCREASING THREAT FOR A WIDESPREAD SWATH OF
HEAVY SNOW AND ICE TO THE NORTH OF THE LOW FROM THE CENTRAL PLAINS
TO THE MIDWEST/GREAT LAKES THEN NORTHEAST. THE STRONG WINDS COULD
POSE A COASTAL FLOODING RISK ALONG THE EAST COAST AHEAD OF THE
STORM, WHILE BLOWING AND DRIFTING OF SNOW WOULD BE A THREAT IN THE
COLD SECTOR.
ADDITIONAL DYNAMIC SYSTEMS IN THE SERIES LOOK TO MOVE INTO THE
PACIFIC NORTHWEST EARLY NEXT WEEK WITH ROUNDS OF MODERATE TO HEAVY
RAINFALL EXPECTED FOR THE COASTAL RANGES AND FOOTHILLS OF THE
WA/OR CASCADES. GIVEN THE ONGOING WET PATTERN ACROSS THIS REGION
LATER THIS WEEK/THIS WEEKEND, THE DAY 5/MONDAY EXCESSIVE RAINFALL
OUTLOOK MAINTAINS A MARGINAL RISK AREA FOR THIS REGION. DETAILS
OF THIS EVENT ARE CURRENTLY AMBIGUOUS THOUGH, WITH THE AVERAGE OF
GUIDANCE SUGGESTING THE BEST PERSISTENCE OF ANOMALOUS MOISTURE IN
THE SOUTHERN HALF OF THE RISK AREA VERSUS SOME ENSEMBLE/MODEL
GUIDANCE SHOWING THE BEST QPF SIGNAL FARTHER NORTH. EXPECT HEAVY
SNOW IN THE HIGHER TERRAIN OF THE CASCADES. RAIN AND MOUNTAIN
SNOW SHOULD ALSO EXTEND INTO PARTS OF THE INTERIOR WEST/ROCKIES
THROUGH MID-LATE WEEK. PRECIPITATION OF VARIOUS TYPES COULD
DEVELOP OVER THE CENTRAL U.S. BY AROUND THURSDAY AS LOW PRESSURE
REACHES THE REGION.
TEMPERATURES SHOULD GENERALLY TREND COOLER ACROSS MUCH OF THE
WESTERN U.S. AND AT TIMES EXTENDING INTO THE HIGH PLAINS NEXT WEEK
AS MEAN TROUGHING ALOFT REMAINS ANCHORED OVER THE REGION. THERE
SHOULD BE DECENT COVERAGE OF DAYTIME HIGHS 5-15F BELOW NORMAL
SUNDAY-MONDAY WITH SOME SLIGHT MODERATION AROUND TUESDAY, FOLLOWED
BY ANOTHER COLDER TREND THURSDAY THAT WOULD LEAD TO MORE HIGHS
5-15F BELOW NORMAL. SOME HIGHS MAY BE UP TO 20-30F BELOW NORMAL
OVER THE NORTHERN HIGH PLAINS AT THAT TIME. AHEAD OF THE NEXT
STORM SYSTEM IN THE CENTRAL U.S. EARLY NEXT WEEK, TEMPERATURES
ACROSS THE EAST WILL LIKELY BE MODERATELY ABOVE NORMAL WITH THE
GREATEST ANOMALIES BEING FOR MORNING LOWS ACROSS THE GREAT
LAKES/NORTHEAST.
RAUSCH/SANTORELLI
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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