811
FXUS02 KWBC 110658
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EDT FRI OCT 11 2024
VALID 12Z MON OCT 14 2024 - 12Z FRI OCT 18 2024
..OVERVIEW
DURING THE EARLY PART OF NEXT WEEK, UPPER TROUGHING WILL SETTLE IN
ACROSS THE EASTERN HALF OF THE U.S., LEADING TO BELOW NORMAL
TEMPERATURES ALONG WITH FROST/FREEZE CONCERNS FOR THE NORTH-CENTRAL
U.S. TO NORTHEAST. PRECIPITATION WILL BE LIKELY EARLY WEEK IN THE
NORTHEASTERN U.S., WHILE MORE UNCERTAIN LIGHT RAIN MAY FALL IN THE
SOUTHEAST, AND SOUTHERN FLORIDA SHOULD SEE ROUNDS OF THUNDERSTORMS.
MEANWHILE THE WESTERN U.S. CAN EXPECT MEAN UPPER RIDGING (ASIDE
FROM EMBEDDED ENERGY) EARLY NEXT WEEK, WHICH IS FORECAST TO SHIFT
EASTWARD INTO THE CENTRAL U.S. THROUGH THE WEEK WITH WARMER THAN
AVERAGE TEMPERATURES UNDERNEATH IT. THE PATTERN IN THE WEST IS
FORECAST TO FLIP TO TROUGHING BY MIDWEEK TO LATE WEEK WITH A COUPLE
ROUNDS OF REINFORCING ENERGY. THIS WILL COOL TEMPERATURES THERE
AND LEAD TO INCREASING PRECIPITATION CHANCES, INCLUDING HIGHER
ELEVATION SNOW.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE SHOWS REASONABLY GOOD AGREEMENT EARLY IN THE
FORECAST PERIOD, WITH BROAD TROUGHING ACROSS THE MIDWEST TO EAST
ANCHORED BY A GREAT LAKES UPPER LOW WHILE GENERAL RIDGING IN THE
WEST IS BROKEN UP BY AN EMBEDDED SOUTHERN STREAM UPPER LOW ATOP THE
CENTRAL GREAT BASIN MONDAY. A SURFACE LOW IN THE NORTHEAST
CONTINUES TO HAVE SOME PLACEMENT SPREAD, BUT A MORE INLAND TRACK
LIKE THE 18Z GFS/12Z ECMWF SEEMED MOST AGREEABLE WITH THE ENSEMBLE
MEANS. THE TROUGH IN THE EAST SHOULD GRADUALLY SWEEP EASTWARD
TUESDAY-WEDNESDAY BUT THERE IS CONTINUED UNCERTAINTY WITH WHETHER
OR NOT ENERGY BREAKS OFF IN THE SOUTHERN PART OF THE TROUGH TO FORM
A POSSIBLE CLOSED LOW. A MINORITY OF MODELS SHOW THIS TYPE OF
SOLUTION, INCLUDING THE 12Z GFS (BUT NOT THE 18Z OR 00Z RUN) AND
THE 12Z CMC, AND AN AI/ML MODEL RUN OR TWO. A SOLUTION LIKE THAT
WOULD BRING MORE RAINFALL INTO THE SOUTHEAST AND SPIN UP A
SOUTHEAST OR WESTERN ATLANTIC SURFACE LOW. HOWEVER, THE MAJORITY OF
GUIDANCE (ESPECIALLY WHEN CONSIDERING THE NEWER 00Z CYCLE) DEPICTS
AN OPEN TROUGH, AND WPC CONTINUES TO FAVOR THAT FOR A SINGLE
DETERMINISTIC FORECAST. THERE IS ALSO SOME QUESTION REGARDING THE
WIDTH OF THE TROUGH DEPENDENT ON SHORTWAVE POSITIONS, BUT A BLEND
OF THE 18Z GFS/12Z ECMWF AND THEIR MEANS SEEMED REASONABLE AT THIS
POINT THOUGH THE TROUGH MAY END UP NARROWER PER MANY AI/ML MODELS.
IN THE WEST, THERE IS BETTER THAN NORMAL LARGE SCALE AGREEMENT FOR
THE UPPER TROUGH TO MOVE GRADUALLY INLAND TUESDAY AND BEYOND WITH
REINFORCING SHORTWAVE ENERGIES. HOWEVER, DETAIL DIFFERENCES LIKE
THESE SHORTWAVES AND THEIR TIMING AND PLACEMENT HAVE SENSIBLE
WEATHER DIFFERENCES LIKE THE STRENGTH OF THE ASSOCIATED ATMOSPHERIC
RIVER (ECMWF SHOWING STRONGER THAN THE GFS) AND TIMING OF
PRECIPITATION. FOR NOW PREFER A MIDDLE GROUND APPROACH RATHER THAN
LEANING TOWARD ANY PARTICULAR MODEL SOLUTION.
THE WPC FORECAST USED A BLEND FAVORING THE DETERMINISTIC 18Z GFS
AND 12Z ECMWF WITH SMALLER PROPORTIONS OF THE CMC AND ENSEMBLE
MEANS EARLY IN THE PERIOD. GRADUALLY INCREASED THE PROPORTION OF
THE ENSEMBLE MEANS TO OVER HALF BY DAYS 6-7 AMID INCREASING
UNCERTAINTY (WHILE ALSO ELIMINATING THE 12Z CMC GIVEN ITS EVENTUAL
OUTLIER STATUS ACROSS THE EAST).
..WEATHER/HAZARDS HIGHLIGHTS
LOW PRESSURE IN THE NORTHEAST AS THE PERIOD BEGINS ON MONDAY WILL
LEAD TO SOME LIGHT TO MODERATE PRECIPITATION THERE, AND BEHIND THE
SYSTEM PASSAGE LAKE-ENHANCED AND TERRAIN-ENHANCED PRECIPITATION IS
FORECAST ACROSS THE GREAT LAKES REGION TO INTERIOR NORTHEAST
TUESDAY-WEDNESDAY. COLDER TEMPERATURES SHOULD ALLOW FOR SNOW
ESPECIALLY IN THE HIGHER ELEVATIONS. FARTHER SOUTH, THERE MAY BE
SOME RAIN ALONG A FRONT IN THE SOUTHEAST ON MONDAY-TUESDAY
DEPENDING ON THE EVOLUTION OF THE UPPER TROUGH AND SURFACE
FEATURES. THEN ACROSS SOUTH FLORIDA, SOME INSTABILITY AND HIGH PWS
NEAR A FRONTAL BOUNDARY WILL LEAD TO RAIN AND THUNDERSTORMS IN THE
VICINITY. THERE IS STILL SOME UNCERTAINTY IN RAINFALL AMOUNTS AND
HOW MUCH RAIN FALLS OFFSHORE VERSUS ONSHORE, BUT THERE MAY BE A
NONZERO CHANCE OF FLASH FLOODING ESPECIALLY IF AREAS GET HIT WITH
HEAVY RAINFALL MULTIPLE TIMES, AND CONSIDERING INITIALLY WET GROUND
CONDITIONS. THERE SHOULD BE LESSENING PRECIPITATION COVERAGE
ACROSS THE EAST BEHIND A SECONDARY COLD FRONT AS THE WEEK
PROGRESSES.
THE DEVELOPING AND RELOADING UPPER TROUGH AND MULTIPLE SURFACE
FRONTS MOVING INTO THE WEST WILL GRADUALLY PUSH PRECIPITATION INTO
THE NORTHERN/CENTRAL WEST COAST BY TUESDAY AND THROUGH THE NORTHERN
ROCKIES INTO WEDNESDAY-THURSDAY. WHILE THERE IS GOOD CONFIDENCE IN
THE OVERALL EVENT, UNRESOLVED SPECIFICS OF THE UPPER TROUGH LEAD
TO GREATER UNCERTAINTY WITH RESPECT TO THE SOUTHWARD/EASTWARD
EXTENT OF PRECIPITATION AS WELL AS MAGNITUDE. EXPECT RELATIVELY
HIGHER TOTALS OVER FAVORED COASTAL AREAS AND THE CASCADES. HIGHER
ELEVATION SNOW WILL BE POSSIBLE BY MIDWEEK, WHICH MAY BE THE FIRST
SNOW OF THE SEASON IN SOME LOCATIONS GIVEN THE WARM FALL IN THE
WEST THUS FAR.
AN UPPER RIDGE ALIGNED OVER THE ROCKIES INTO EARLY NEXT WEEK AND
THEN SHIFTING EASTWARD BY MID- AND LATER WEEK WILL PROMOTE WELL
ABOVE NORMAL TEMPERATURES IN ITS VICINITY. THE BIGGEST ANOMALIES
ARE FORECAST ACROSS THE NORTHERN ROCKIES AND HIGH PLAINS MONDAY-
WEDNESDAY, WHERE HIGHS INTO THE 70S AND 80S ARE 15-25 DEGREES ABOVE
AVERAGE FOR MID-OCTOBER. THESE WARM TEMPERATURES WILL SHIFT INTO
MUCH OF THE PLAINS AND MIDWEST BY THURSDAY-FRIDAY. FOR MUCH OF THE
EASTERN U.S., TEMPERATURES ARE FORECAST TO GRADUALLY COOL MONDAY-
WEDNESDAY AS A COOL SURFACE HIGH PRESSURE SYSTEM SETTLES IN BEHIND
A COLD FRONT. MORNING LOWS MAY CAUSE FROST/FREEZE CONCERNS FROM THE
NORTH-CENTRAL U.S. THROUGH THE MIDWEST/GREAT LAKES AND
NORTHEAST/APPALACHIANS. EXPECT SOME MODERATION THERE BY THURSDAY-
FRIDAY. THE GULF COAST STATES CAN EXPECT ABOVE AVERAGE TEMPERATURES
INTO MONDAY, AND A FEW RECORD HIGHS ARE POSSIBLE INTO SOUTHERN
TEXAS, BEFORE THE COLD FRONT PUSHES THROUGH. LATER WEEK UPPER
TROUGHING WILL PRODUCE COOLER THAN NORMAL TEMPERATURES FIRST FOR
THE WEST COAST AROUND WEDNESDAY AND SPREADING INTO THE GREAT BASIN
AND ROCKIES THURSDAY-FRIDAY.
TATE
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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