631
FXUS02 KWBC 102039
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
438 PM EDT TUE OCT 10 2023
VALID 12Z FRI OCT 13 2023 - 12Z TUE OCT 17 2023
...EXCESSIVE RAIN THREAT SHIFTS FROM THE UPPER MIDWEST THROUGH THE
NORTHERN MID-ATLANTIC/NORTHEAST FRIDAY THROUGH SATURDAY...
..OVERVIEW
A DYNAMIC UPPER TROUGH/CLOSED LOW AND DEEPENED SURFACE LOW/FRONTAL
SYSTEM WILL STEADILY TRACK FROM THE PLAINS THROUGH THE NORTHEAST
FRIDAY THROUGH THIS WEEKEND. THIS WILL FOSTER THE SPREAD OF HEAVY
PRECIPITATION FROM THE UPPER MIDWEST THROUGH THE NORTHERN
MID-ATLANTIC/NORTHEAST AS INFLOW MOISTURE INCREASES AND IS
SUSTAINED WITH ADDITION INFLUX FROM THE ATLANTIC. TO THE SOUTH, A
FRONTAL BOUNDARY ENHANCED WITH TROPICAL MOISTURE WILL LIFT FROM
THE GULF OF MEXICO TO SPREAD HEAVY PRECIPITATION ACROSS THE
SOUTHEAST THROUGH FRIDAY BEFORE LIFTING OFFSHORE. OUT WEST, AN
AMPLIFYING RIDGE OVER THE INTERMOUNTAIN WEST WILL ALLOW TROUGHING
TO REBUILD THE PACIFIC NORTHWEST, ALLOWING A WET PERIOD THIS
WEEKEND WELL INTO NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THERE IS GOOD OVERALL AGREEMENT ON THE PROGRESSION OF THE PLAINS
LOW AND THE EASTERN CANADA LOW THROUGH THIS WEEKEND. A KEY FEATURE
RESPONSIBLE FOR SOME OF THE CHANGES IS SHORTWAVE ENERGY ROUNDING
THE NORTH OF THE CANADIAN LOW WEDNESDAY THAT THEN TRACKS NORTH OF
THE LOW OVER THE PLAINS THURSDAY. THE 00Z ECMWF/UKMET PHASE THIS
WAVE INTO THE PLAINS LOW, TRIGGERING A DEEPER, SLOWER LOW OVER THE
GREAT LAKES/NORTHEAST THIS WEEKEND WHILE THE 00Z CMC/06Z GFS LEFT
THE ENERGY SEPARATE/DRIFTING OVER THE CANADIAN PRAIRIES THIS
WEEKEND. PREFERENCE WAS GIVEN TO THE 00Z EC/UK SOLUTION GIVEN THE
06Z CMC REGIONAL TRENDED TOWARD A PHASING LOW. BOTH THE 12Z
CMC/GFS HAVE TRENDED THIS WAY (BUT STILL DO NOT PHASE) WHILE THE
12Z UKMET HAS SOME SEPARATION AND AN OVERALL MUCH WEAKER LOW. THE
12Z ECMWF IS DELAYED TODAY AND NOT AVAILABLE FOR DIAGNOSIS BY
PUBLISH TIME. THE WPC PRODUCT SUITE WAS DERIVED FROM A BLEND
WEIGHTED TOWARD THE 00Z ECMWF/UKMET WITH THE 06Z GEFS EARLY ON,
TRANSITIONING TO THE 00Z ECMWF WITH THE 00Z ECENS/06Z GEFS AFTER
DAY 5 BASED ON THE GENERAL PATTERN OF A TROUGH ALONG THE NORTHERN
WEST COAST, RIDGE OVER THE WEST-CENTRAL, AND TROUGH/LOW OVER THE
EAST-CENTRAL CONUS. QPF COMBINED THE 13Z NBM WITH THE 00Z ECMWF
AND SOME UKMET OVER THE EASTERN HALF OF THE CONUS, WITH A GENERAL
MODEL BLEND FOR THE PACIFIC NORTHWEST.
..WEATHER/HAZARDS HIGHLIGHTS
A WELL DEVELOPED LOW PRESSURE SYSTEM SHIFTING EAST FROM THE
CENTRAL PLAINS TO THE GREAT LAKES FRIDAY THEN TO THE NORTHEAST
THROUGH SATURDAY NIGHT WRAPS ANOMALOUS MOISTURE INTO WARM/OCCLUDED
FRONTS WHICH PROVIDE A FOCUS FOR HEAVY RAINS. WHILE LONGER
DURATION RAINS AND AMBIENT RELATIVELY DRY SOILS MAY PARTIALLY
LIMIT IMPACT, THE WPC DAY 4/FRIDAY EXCESSIVE RAINFALL OUTLOOKS
(ERO) MAINTAIN A SLIGHT RISK OVER THE UPPER MIDWEST WITH A BIT OF
A NORTHWARD SHIFT GIVEN LATEST GUIDANCE. THE DAY 5/SATURDAY ERO
HAS AN EXPANDED SLIGHT RISK OVER THE NORTHERN MID-ATLANTIC GIVEN A
NORTHWARD SHIFT IN HEAVY RAIN FOCUS AS ATLANTIC MOISTURE IS
CONCENTRATED NORTH OF THE REDEVELOPING SYSTEM ALONG THE
MID-ATLANTIC COAST.
MEANWHILE, A SEPARATE FRONT MEANDERING THROUGH THE GULF OF MEXICO
AND THE FLORIDA PENINSULA LIFTING IN ADVANCE OF THE AFOREMENTIONED
MAIN STORM WILL BRING SPREAD A THREAT FOR HEAVY RAINFALL ACROSS
THE SOUTHEAST INTO FRIDAY NIGHT. THIS MAY BE AIDED BY AN AREA OF
LOW PRESSURE IN THE GULF OF MEXICO THAT IS NOW BEING MONITORED BY
NHC AND POSSIBLE EASTERN PACIFIC REMNANT TROPICAL MOISTURE. THE
DAY 4/FRIDAY ERO MARGINAL RISK WAS TRIMMED A BIT OVER SOUTH
CAROLINA AND MAINTAINED SOUTH OF THERE INTO NORTH FLORIDA.
WIDESPREAD ENHANCED WINDS ARE FORECAST ON THE BACKSIDE OF THE LOW
FIRST IN THE PLAINS/UPPER MIDWEST AND THEN AGAIN OVER THE
NORTHEAST AS THE LOW REDEVELOPS ALONG THE COAST. THE ASSOCIATED
COLD FRONT WILL ALSO SPREAD COOLER THAN AVERAGE TEMPERATURES FROM
WEST TO EAST ACROSS THE LOWER 48, WITH A FIRST FROST/FREEZE OF THE
FALL SEASON POSSIBLE IN THE CENTRAL PLAINS. THIS COLD FRONT
CROSSES ALL OF FLORIDA SATURDAY INTO SUNDAY, BRINGING RELIEF TO A
STRING OF NEAR RECORD HIGHS OVER SOUTH FLORIDA SUNDAY.
STRONG TROUGHING OVER THE PACIFIC NORTHWEST/NORTHWEST EARLY NEXT
WEEK BRINGS LIKELY MODERATE RAINFALL ALONG WITH SOME HIGH
ELEVATION SNOW.
JACKSON
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
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE UPPER/MIDDLE MISSISSIPPI
VALLEY AND THE GREAT LAKES, FRI, OCT
13.
- HEAVY RAIN ACROSS PORTIONS OF THE GREAT LAKES, THE MID-ATLANTIC,
THE NORTHEAST, THE CENTRAL
APPALACHIANS, AND THE OHIO VALLEY, SAT, OCT 14.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS.
- HIGH WINDS ACROSS PORTIONS OF THE GREAT PLAINS, FRI, OCT 13.
- FROST/FREEZE ACROSS PORTIONS OF THE CENTRAL ROCKIES AND THE
CENTRAL/SOUTHERN PLAINS, FRI-SAT, OCT
13-OCT 14.
- HEAVY RAIN ACROSS PORTIONS OF MAINLAND ALASKA, SAT-SUN, OCT
14-OCT 15.
- HEAVY RAIN ACROSS PORTIONS OF THE ALASKA PANHANDLE AND MAINLAND
ALASKA, FRI, OCT 13.
- HIGH WINDS ACROSS PORTIONS OF THE ALEUTIANS, FRI, OCT 13.
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page