397
FXUS02 KWBC 020700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM 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 MEDIUM RANGE PERIOD FEATURES A RATHER PROGRESSIVE FLOW PATTERN
AS A PARADE OF STORM SYSTEMS TRAVERSES THE COUNTRY FROM WEST TO
EAST. THE FIRST WILL BE MOVE 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. 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 GUIDANCE CONTINUES TO SHOW ABOVE AVERAGE AGREEMENT ON THE
OVERALL SYNOPTIC SCALE FLOW PATTERN, BUT PLENTY OF UNCERTAINTY IN
THE DETAILS. FOR THE INITIAL SYSTEM OUT OF THE SOUTHERN PLAINS ON
FRIDAY, GUIDANCE AGREES THAT A SURFACE LOW WILL DEVELOP ALONG THE
CENTRAL GULF COAST AND 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). GENERALLY, THERE SEEMS TO BE AN OVERALL TREND
TOWARDS A FASTER SURFACE LOW, THOUGH THE UKMET REMAINS THE
QUICKEST. 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. THE WPC FORECAST TONIGHT RELIED ON A
NON-UKMET BLEND FOR THIS SYSTEM.
THE NEXT 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. GIVEN THE
LATE PERIOD TIMING, THE WPC FORECAST GENERALLY STUCK CLOSE TO THE
ENSEMBLE MEANS, WITH A TRACK FARTHER SOUTH CLOSER TO THE
DETERMINISTIC GFS AND ECMWF.
..WEATHER/HAZARDS HIGHLIGHTS
UPPER LOW/TROUGH INTO THE SOUTHERN PLAINS ON FRIDAY SHOULD TAP
PLENTY OF GULF OF MEXICO MOISTURE TO FUEL A ROUND OF 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. 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. EXACT AMOUNTS AND PRECIPITATION TYPE FOR SOME OF
THE MAJOR EAST COAST CITIES REMAINS HIGHLY UNCERTAIN AT THIS
POINT, BUT DOES NEED TO BE WATCHED. 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.
ABOVE NORMAL TEMPERATURES FOR THIS WEEKEND SHOULD BE MOSTLY
CONFINED TO THE FAR NORTHERN TIER 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 SHOULD SEE 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.
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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