256
FXUS02 KWBC 021901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST TUE JAN 02 2024
VALID 12Z FRI JAN 05 2024 - 12Z TUE JAN 09 2024
...MAJOR STORM SYSTEM TO BRING HAZARDOUS WEATHER FROM THE GULF
COAST NORTHEASTWARD FRIDAY-SUNDAY...
..OVERVIEW
THE EXTENDED PERIOD WILL BE ACTIVE AS A SERIES OF STORM SYSTEMS
TRACK WEST TO EAST. THE LEADING SYSTEM MOVES FROM THE SOUTHERN
PLAINS ON FRIDAY INTO THE EASTERN U.S. BY THIS WEEKEND, WITH
INCREASING POTENTIAL FOR HEAVY PRECIPITATION (RAIN TO THE SOUTH,
SNOW TO THE NORTH) FROM THE GULF COAST NORTHEASTWARD. 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
AND WEST OF THE LOW.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST RUNS OF GUIDANCE MAINTAINS ABOVE AVERAGE CONFIDENCE FOR
THE ACTIVE LARGE SCALE PATTERN DURING THIS PERIOD. THE LEADING
SYSTEM WILL HAVE A SURFACE LOW DEVELOP ALONG THE CENTRAL GULF
COAST THAT WILL TRACK THROUGH THE SOUTHEAST, DEEPENING FURTHER AS
IT EXITS THE MID-ATLANTIC EARLY SUNDAY. THERE CONTINUES TO BE SOME
KEY DIFFERENCES REGARDING TIMING AND EXACT TRACK OF THE LOW, WHICH
HAS HUGE IMPLICATIONS FOR PRECIPITATION TYPE, ESPECIALLY FOR MORE
EASTERN AREAS (INCLUDING MAJOR CITIES IN THE DC TO NYC CORRIDOR).
AS NOTED WITH THE PREVIOUS FORECAST, THE UKMET IS ON THE FASTER
SIDE OF CONSENSUS AND WAS AVOIDED FOR THIS FORECAST. THERE ARE
ALSO LOTS OF UNCERTAINTY WITH THE EXACT NORTHWARD EXTENT OF THE
TRACK TOO, AND THE MEDIUM TO SMALLER SCALE SHORTWAVE DETAILS WITH
LOWER PROBABILITY MAY HAVE A SIGNIFICANT EFFECT ON SURFACE
EVOLUTION, SO ADDITIONAL ADJUSTMENTS IN THE GUIDANCE APPEARS
LIKELY.
MEANWHILE, ANOTHER TROUGH ENTERS THE PACIFIC NORTHWEST LATE
FRIDAY/EARLY SATURDAY AND THE GUIDANCE SHOWS GENERALLY GOOD
AGREEMENT THAT IT WILL AMPLIFY OVER THE WEST BEFORE EJECTING INTO
THE PLAINS AROUND MONDAY. GUIDANCE SHOWS GOOD AGREEMENT THAT A
SURFACE LOW SPINS UP NEAR THE TEXAS/OKLAHOMA PANHANDLE EARLY
MONDAY GENERALLY TRACKING EAST-NORTHEASTWARD INTO THE MIDDLE
MISSISSIPPI VALLEY ON TUESDAY. THERE IS SIGNIFICANT UNCERTAINTY
THOUGH ON THE EXACT TRACK, WITH THE CMC BEING NORTH OF THE OVERALL
BETTER CONSENSUS. THE CMC, ECWMF, GFS AND THEIR RESPECTIVE
ENSEMBLE MEANS CONTINUE TO PROVIDE A SOLID SOLUTION AND THIS
MAINTAINS WPC CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER LEVEL LOW/TROUGH OVER THE SOUTHERN PLAINS FRIDAY WILL
HAVE AN ABUNDANCE OF MOISTURE FROM THE GULF TO AID IN FUELING
MODERATE TO LOCALLY HEAVY RAINFALL ACROSS THE LOWER MISSISSIPPI
VALLEY/CENTRAL GULF COAST STATES AND PERHAPS NEARBY AREAS ON
FRIDAY. THE DAY 4 EXCESSIVE RAINFALL OUTLOOK MAINTAINS A MARGINAL
RISK AREA EXTENDING FROM SOUTHEAST TEXAS TO THE FLORIDA PANHANDLE.
THERE IS SOME QUESTION ABOUT HOW FAR NORTHWARD INSTABILITY MAY
EXTEND, BUT ANOMALOUS MOISTURE AND A LEADING FRONT FORMING NEAR
THE GULF COAST TO PROVIDE A FOCUS, PLUS FAIRLY WET ANTECEDENT
CONDITIONS FROM SHORT-TERM RAINFALL, SEEM TO SUGGEST SOME FLASH
FLOODING POTENTIAL. ONLY MINOR ADJUSTMENTS WERE MADE TO THE
INHERITED RISK AREA FOR THIS PERIOD. HEAVY PRECIPITATION WILL
SPREAD ACROSS THE SOUTHEAST/MID-ATLANTIC AND POSSIBLY THE
NORTHEAST THIS COMING WEEKEND, WITH INCREASING POTENTIAL FOR HEAVY
SNOW TO THE NORTH AND WEST OF THE LOW. UNCERTAINTY PERSISTS ON THE
EXACT AMOUNTS AND PRECIPITATION TYPE FOR SOME OF THE MAJOR EAST
COAST CITIES GIVEN THE SPREAD IN MODEL GUIDANCE. THE WPC WINTER
WEATHER OUTLOOK PROBABILITIES HIGHLIGHT THE BEST POTENTIAL FOR AT
LEAST 0.25" LIQUID IN THE FORM OF SNOW OVER THE CENTRAL
APPALACHIANS/INTERIOR MID-ATLANTIC. JUST TO THE EAST, GUIDANCE
TRENDS DO SHOW SOMEWHAT HIGHER PROBABILITIES FOR ACCUMULATING
SNOWFALL NEAR THE DC-NYC CORRIDOR BUT HIGHLY DEPENDENT ON THE
EXACT TRACK OF THE LOW AS SUFFICIENTLY COLD TEMPERATURES IN THIS
PARTICULAR REGION REMAIN MARGINAL AT BEST. IT WILL CONTINUE TO
TAKE SOME TIME TO RESOLVE IMPORTANT DETAILS GIVEN THE CURRENT
SPREAD FOR SURFACE LOW TIMING/TRACK.
A SMALLER-SCALE SYSTEM MAY BRING A BRIEF FOCUS OF ENHANCED
RAIN/MOUNTAIN SNOW TO THE PACIFIC NORTHWEST AROUND FRIDAY. THEN
EXPECT BROADER COVERAGE OF MODERATE TO LOCALLY HEAVY PRECIPITATION
FROM THE WEST COAST/CALIFORNIA AND INTO THE INTERIOR WEST BY NEXT
MONDAY. THERE IS A DECENT SIGNAL FOR MEANINGFUL MOUNTAIN SNOWS
ACROSS PARTS OF THE CASCADES, SIERRA NEVADA, AND INTERIOR MOUNTAIN
RANGES/SOUTHERN ROCKIES. SURFACE CYCLOGENESIS ACROSS THE
SOUTH-CENTRAL PLAINS EARLY NEXT WEEK SHOULD ALLOW PRECIPITATION TO
MOVE INTO THE CENTRAL U.S., WITH POTENTIAL FOR MODERATE TO HEAVY
SNOW TO THE NORTH OF THE LOW TRACK.
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. NORTHERN
PARTS OF THE WEST SHOULD TREND BELOW NORMAL AS WELL.
CAMPBELL/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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