105
FXUS02 KWBC 011835
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 PM EDT SUN OCT 01 2023
VALID 12Z WED OCT 04 2023 - 12Z SUN OCT 08 2023
...HEAVY RAIN AND FLASH FLOODING THREAT FOR THE SOUTH-CENTRAL U.S.
BY MIDWEEK...
..OVERVIEW
AN AMPLIFIED UPPER TROUGH WILL BE IN PLACE WITH ITS AXIS NEAR THE
HIGH PLAINS MIDWEEK. MOIST AND UNSTABLE INFLOW AHEAD OF THE TROUGH
AND AN ASSOCIATED WAVY COLD FRONT SHOULD LEAD TO WIDESPREAD HEAVY
RAIN AND FLASH FLOODING ACROSS THE SOUTHERN PLAINS WEDNESDAY INTO
THURSDAY. FARTHER NORTH, THE COLD FRONT MARCHING EASTWARD SHOULD
HELP CAUSE SOME RAIN TO PUSH ACROSS THE EAST-CENTRAL AND EASTERN
U.S. THROUGH THE LATTER HALF OF THE WEEK, AS WELL AS SPREAD COOLER
THAN NORMAL TEMPERATURES BEHIND IT AFTER A WARM SPELL IN THE GREAT
LAKES/OHIO VALLEY INTO THE NORTHEAST AROUND MIDWEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE FOR THIS COMING WEDNESDAY AND
THURSDAY WAS PRIMARILY DERIVED FROM A BLEND OF THE 00 UTC
ECMWF/UKMET AND ECMWF ENSEMBLE MEAN THAT ALONG WITH THE 00 UTC
CANADIAN HANG BACK MORE AMPLE UPPER TROUGHING OVER THE SOUTHWEST
THAN THE 06 UTC GFS/GEFS THAT SEEM TOO PROGRESSIVE WITH ENERGIES
GIVEN UPSTREAM UPPER RIDGE AMPLITUDE. THE ECMWF/UKMET AND ECMWF
ENSEMBLES ARE OVERALL BEST CLUSTERED IN THIS TIME FRAME ACROSS THE
FORECAST DOMAIN. FORECAST SPREAD INCREASES FRIDAY INTO THE WEEKEND
AND THE MODELS OFFER LESS THAN STELLAR RUN TO RUN CONTINUITY WITH
MIXED ENSEMBLE SUPPORT. ACCORDINGLY, PREFER MORE COMPATIBLE
GUIDANCE FROM THE 06 UTC GEFS AND 00 UTC ECMWF ENSEMBLE MEANS,
THIS SOLUTION FOLLOWS A TREND WITH NORTHERN STREAM FLOW
AMPLIFICATION AND 12 UTC MODEL TRENDS REMAIN GENERALLY IN LINE.
OVERALL, THE PATTERN EVOLUTION SEEMS TO HAVE NEAR AVERAGE
PREDICTABILITY. WPC PRODUCT CONTINUITY SEEMS REASONABLY WELL
MAINTAINED.
..WEATHER/HAZARDS HIGHLIGHTS
THE SOUTH-CENTRAL U.S. WILL BE AN AREA OF FOCUS FOR WIDESPREAD
HEAVY RAIN ESPECIALLY ON WEDNESDAY, AS THE RIGHT ENTRANCE REGION
OF THE JET WILL PROVIDE AMPLE LIFT, AND PLENTY OF INSTABILITY IS
IN PLACE JUST AHEAD OF THE COLD FRONT. A SLIGHT RISK REMAINS IN
PLACE THERE IN THE DAY 4/WEDNESDAY EXCESSIVE RAINFALL OUTLOOK, AS
DESPITE THE DROUGHT CONDITIONS, HIGH RAIN RATES THAT COULD
OVERCOME THE DRYNESS ARE LIKELY. BY THURSDAY, THE COLD FRONT WILL
PUSH SOUTHEAST AND CLEAR OUT RAIN POTENTIAL ON ITS BACKSIDE, BUT
COULD STILL PROVIDE FORCING FOR CONVECTION ALONG AND AHEAD OF IT
INTO SOUTHERN AND EASTERN PARTS OF TEXAS AND INTO THE LOWER
MISSISSIPPI VALLEY. MODEL GUIDANCE STILL VARIES WITH PLACEMENT OF
ANY HEAVY AMOUNTS, BUT ENSEMBLE AND CLUSTERING SIGNALS ARE GROWING
TO FAVOR ISSUANCE OF A SMALL SLIGHT RISK AREA OVER TEXAS FOR THE
DAY 5/THURSDAY ERO TO COVER THE THREAT. SOME LINGERING RAIN MAY BE
POSSIBLE IN SOUTH TEXAS LATE WEEK.
FARTHER NORTH, THE COLD FRONT SHOULD TRACK THROUGH THE
MIDWEST/UPPER GREAT LAKES AND THE OHIO/TENNESSEE VALLEYS WEDNESDAY
INTO FRIDAY, THE INTO THE EAST HEADING INTO THE WEEKEND, PRODUCING
SHOWERS AND THUNDERSTORMS ALONG AND AHEAD OF IT. THIS RAIN SHOULD
OVERALL BE LIGHTER THAN FARTHER SOUTH, BUT MAY BE ENHANCED IN THE
NORTHEAST ESPECIALLY IN FAVORED TERRAIN, AS THE FRONT COULD BEGIN
TO TAP ATLANTIC MOISTURE WITHIN SOUTHERLY FLOW TO INCREASE
RAINFALL, ESPECIALLY CONSIDERING PREFERENCE FOR AN AMPLIFIED
SUPPORTING UPPER TROUGHING BY LATE WEEK.
THE AMPLIFIED TROUGH AND THE COLD FRONT WILL LEAD TO COOLER
TEMPERATURES THAN AVERAGE WHILE THE UPPER RIDGES TO THE EAST AND
WEST WILL SUPPORT ABOVE NORMAL TEMPERATURES. THE INTERIOR WEST
SHOULD SEE COOLER TEMPERATURES THAN AVERAGE ESPECIALLY THROUGH
MIDWEEK, WITH WITH LOWS 5-10F BELOW NORMAL AND HIGHS AROUND 10-15F
BELOW AVERAGE, BUT WARMING TO NEAR NORMAL FOR THE LATTER PART OF
THE WEEK. MEANWHILE WARMER THAN AVERAGE TEMPERATURES BY AROUND
15-20F ABOVE NORMAL ARE FORECAST MIDWEEK FOR THE MIDWEST INTO THE
GREAT LAKES AND THE INTERIOR NORTHEAST, WITH HIGHS IN THE UPPER
70S TO LOW 80S. SOME DAILY RECORDS FOR HIGHS/WARM LOWS MAY BE
POSSIBLE WEDNESDAY. AS THE COLD FRONT AND UPPER TROUGH MARCH EAST
INTO THE LATTER HALF OF THE WEEK, TEMPERATURES WILL COOL TO BELOW
AVERAGE ACROSS THE CENTRAL AND THEN EAST-CENTRAL U.S., LIMITING
THE ABOVE NORMAL TEMPERATURES TO THE NORTHEAST. A TRAILING FRONT
MAY REINFORCE THE COOLING TREND BY FRIDAY-SUNDAY, AND THERE COULD
BE CONCERNS FOR THE FIRST FROST OR FREEZE OF THE SEASON TO OCCUR
IN THE NORTHERN HIGH PLAINS. APPROACH/ARRIVAL OF THE EASTERN
PACIFIC UPPER RIDGE SHOULD RAISE TEMPERATURES ALONG THE WEST COAST
TO ABOVE AVERAGE, BY AS MUCH AS 5-15F, AND SOME RECORD WARM LOWS
MAY BE POSSIBLE.
SCHICHTEL/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, 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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