717
FXUS02 KWBC 030659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST WED JAN 03 2024
VALID 12Z SAT JAN 06 2024 - 12Z WED JAN 10 2024
...MAJOR STORM SYSTEM TO BRING HAZARDOUS WEATHER ACROSS PARTS OF
THE MID-ATLANTIC AND NORTHEAST THIS WEEKEND...
...A SECOND SIGNIFICANT STORM SYSTEM COULD BRING HEAVY RAIN ACROSS
THE SOUTH-CENTRAL U.S. AND INTO THE EAST EARLY TO MIDDLE OF NEXT
WEEK, WITH HEAVY SNOW TO THE NORTH...
..OVERVIEW
GUIDANCE CONTINUES TO ADVERTISE AN ACTIVE MEDIUM RANGE PERIOD WITH
TWO MAJOR STORM SYSTEMS IN THE FORECAST. THE LEADING SYSTEM MOVES
INTO THE EAST THIS WEEKEND, WITH INCREASING POTENTIAL FOR HEAVY
RAIN NEAR THE COAST, AND HEAVY SNOW ACROSS INTERIOR PORTIONS OF
THE MID-ATLANTIC AND PARTS OF NEW ENGLAND. IN ITS WAKE, THE NEXT
TROUGH DROPS INTO THE WEST THIS WEEKEND AS WELL BRINGING ANOTHER
ROUND OF VALLEY RAIN AND MOUNTAIN SNOWS PROGRESSING FROM
CALIFORNIA INTO THE FOUR CORNERS REGION. CYCLOGENESIS APPEARS
LIKELY ACROSS THE SOUTH-CENTRAL PLAINS BY MONDAY, BRINGING ANOTHER
ROUND OF HEAVY RAINFALL TO PARTS OF THE SOUTH/TENNESSEE VALLEY
REGION MONDAY-TUESDAY, WITH INCREASING SNOW POTENTIAL TO THE NORTH
OF THE LOW TRACK FROM THE CENTRAL PLAINS INTO THE GREAT LAKES AND
INTERIOR NORTHEAST MONDAY-TUESDAY. ANOTHER TROUGH/CLOSED LOW LOOKS
TO MOVE INTO THE PACIFIC NORTHWEST EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST MODEL RUNS CONTINUE TO MAINTAIN ABOVE AVERAGE
CONFIDENCE FOR THE OVERALL LARGE SCALE PATTERN, BUT OFFER PLENTY
OF UNCERTAINTY IN THE DETAILS/TIMING OF INDIVIDUAL SYSTEMS. THE
STRENGTHENING SURFACE LOW LIFTING THROUGH THE SOUTHEAST AND OFF
THE MID-ATLANTIC COAST ON SATURDAY HAS TRENDED FASTER BUT KEY
DIFFERENCES IN EXACT TRACK WOULD HAVE HUGE IMPLICATIONS FOR
PRECIPITATION TYPE, ESPECIALLY FOR MORE EASTERN AREAS (INCLUDING
THE DC-NYC CORRIDOR). THERE IS PLENTY OF WOBBLE IN THE SURFACE LOW
TRACK RUN TO RUN, AND WILL LIKELY TAKE UNTIL THE NEAR TERM TO
FULLY SORT OUT. A BLEND OF THE LATEST DETERMINISTIC GUIDANCE
OFFERED A GOOD STARTING POINT FOR THE FORECAST AND MAINTAINED GOOD
CONTINUITY WITH THE PREVIOUS WPC FORECAST UNTIL MORE CONFIDENCE IS
GLEANED IN ANY SUBSTANTIAL ADJUSTMENTS.
MEANWHILE, ANOTHER TROUGH ENTERS THE PACIFIC NORTHWEST EARLY
SATURDAY AND THE GUIDANCE SHOWS GENERALLY GOOD AGREEMENT THAT IT
WILL AMPLIFY OVER THE WEST BEFORE EJECTING INTO THE PLAINS AROUND
MONDAY. A SURFACE LOW LIKELY SPINS UP NEAR THE TEXAS/OKLAHOMA
PANHANDLE EARLY MONDAY, DEEPENING AS IT GENERALLY TRACKS
EAST-NORTHEASTWARD INTO THE MIDDLE MISSISSIPPI VALLEY ON TUESDAY
AND THE GREAT LAKES BY WEDNESDAY. THERE IS PLENTY OF UNCERTAINTY
THOUGH ON THE EXACT TRACK AND A SOLUTION CLOSEST TO THE ENSEMBLE
MEANS SEEMS TO SUFFICE AT THIS TIME.
YET ANOTHER SYSTEM LOOKS TO ENTER THE PACIFIC NORTHWEST LATE IN
THE PERIOD/EARLY NEXT WEEK, BUT THERE IS A LOT OF UNCERTAINTY IN
BOTH THE STRENGTH AND TIMING OF THIS SYSTEM. WPC PREFERS A BLEND
OF THE ENSEMBLE MEANS TO HELP MITIGATE THE DIFFERENCES AT THESE
LONGER TIME SCALES.
..WEATHER/HAZARDS HIGHLIGHTS
A MAJOR SURFACE LOW TRACKING OFF THE MID-ATLANTIC COAST ON
SATURDAY CONTINUES TO SHOW INCREASING SNOW POTENTIAL TO THE NORTH
OF THE LOW, PRIMARILY FOR PORTIONS OF THE CENTRAL APPALACHIANS AND
INTERIOR MID-ATLANTIC. THERE MAY BE A PERIOD OF FREEZING RAIN/ICE
AS WELL FOR PARTS OF THE CENTRAL APPALACHIANS. CLOSER TO THE
COAST, AND INCLUDING THE MAJOR DC-NYC CORRIDOR, THERE IS PLENTY OF
UNCERTAINTY REGARDING PRECIPITATION TYPE AND AMOUNTS, HIGHLY
DEPENDENT ON THE EXACT TRACK OF THE LOW AND AVAILABILITY OF
SUFFICIENTLY COLD AIR WHICH WILL TAKE WELL INTO THE SHORT RANGE TO
FULLY RESOLVE. THERE IS SOME GUIDANCE SUGGESTING THESE MAJOR
CITIES COULD SEE MODERATE TO HEAVY SNOW ACCUMULATIONS, BUT ALSO
POTENTIAL FOR LITTLE ACCUMULATION AND MORE RAIN. A MARGINAL RISK
FOR FLASH FLOODING REMAINS ON THE DAY 4/SATURDAY EXCESSIVE
RAINFALL OUTLOOK BUT WAS CONFINED MAINLY FOR THE COASTAL CAROLINAS
AND EASTERN MID-ATLANTIC GIVEN A OVERALL FASTER PROGRESSION AND
LACK OF SIGNIFICANT RAINFALL. ACCUMULATING SNOW MAY IMPACT PARTS
OF SOUTHERN/EASTERN NEW ENGLAND AS WELL INTO SUNDAY.
THE NEXT TROUGH INTO THE WEST WILL BRING EXPANDING COVERAGE OF
RAIN AND MOUNTAIN SNOWS ACROSS THE NORTHWEST AND INTO THE FOUR
CORNERS REGION THIS WEEKEND. THERE IS A DECENT SIGNAL FOR
MEANINGFUL MOUNTAIN SNOWS ACROSS PARTS OF THE CASCADES, SIERRA
NEVADA, AND INTERIOR MOUNTAIN RANGES/SOUTHERN ROCKIES. AS THE
PARENT TROUGH EJECTS INTO THE PLAINS, AN AREA OF LOW PRESSURE
LOOKS TO FORM AND DEEPEN AS IT TRACKS NORTHEASTWARD INTO THE
MISSISSIPPI VALLEY AND GREAT LAKES NEXT WEEK. THIS 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 FROM THE STORM PREDICTION
CENTER. RAIN WILL MOVE INTO THE EASTERN U.S. ON TUESDAY AND
DEPENDING ON SNOW ACCUMULATIONS ACROSS PARTS OF THE EAST EARLY IN
THE PERIOD, THIS COULD BRING AN INCREASED RISK FOR FLOODING DUE TO
EXCESSIVE RAIN AND SNOWMELT. A PERIOD OF GUSTY WINDS LOOKS LIKELY
AS WELL ACROSS THE EAST-CENTRAL U.S. AS THIS SYSTEM STRENGTHENS.
THERE IS ALSO AN INCREASING THREAT FOR HEAVY SNOWS TO THE NORTH OF
THE LOW FROM THE CENTRAL PLAINS TOWARDS THE GREAT LAKES, AND
POSSIBLY INTO PARTS OF THE INTERIOR NORTHEAST AS WELL.
THIS WEEKEND ABOVE SEASONAL AVERAGE TEMPERATURES CAN BE EXPECTED
ACROSS THE FAR NORTHERN TIER STATES WITH ANOMALIES GENERALLY PLUS
5-15F FOR HIGHS, AND PERHAPS AS HIGH AS PLUS 15-25F FOR MORNING
LOWS OVER PARTS OF MINNESOTA/WISCONSIN. ABOVE NORMAL TEMPERATURES
ALSO LOOK TO RETURN TO THE SOUTHERN PLAINS/LOWER MISSISSIPPI
VALLEY AND EVENTUALLY THE EAST EARLY NEXT WEEK. THE SOUTHERN
TWO-THIRDS OF THE WEST WILL LIKELY HAVE BELOW NORMAL TEMPERATURES
LATE THIS WEEK, WITH SOME COOLER ANOMALIES AT LEAST 10F BELOW
NORMAL FOR HIGHS SPREADING ACROSS THE WEST INTO THE HIGH PLAINS BY
SUNDAY-TUESDAY AS UPPER TROUGHING MOVES OVER THE REGION. PARTS OF
THE NORTHWEST AND NORTHERN PLAINS SHOULD TREND BELOW NORMAL AS
WELL, WITH MODESTLY BELOW NORMAL TEMPERATURES ACROSS THE SOUTHERN
PLAINS/SOUTHEAST FOLLOWING PASSAGE OF THE STRONG COLD FRONT EARLY
NEXT WEEK.
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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