346
FXUS02 KWBC 050718
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
318 AM EDT SUN MAY 5 2024
VALID 12Z WED MAY 08 2024 - 12Z SUN MAY 12 2024
...MID-SOUTH/OHIO VALLEY EXCESSIVE RAIN/SEVERE THREAT MIDWEEK
SHIFTS TO THE CENTRAL GULF COAST STATES/APPALACHIANS THURSDAY...
..GUIDANCE/PREDICTABILITY ASSESSMENT
RECENT GUIDANCE CYCLES HAVE SHOWN GOOD AGREEMENT FOR THE OVERALL
SYNOPTIC PATTERN, ALBEIT WITH LOCAL UNCERTAINTIES. A BLEND OF BEST
CLUSTERED GUIDANCE FROM THE GFS/ECMWF MODELS AND TO A LESSER
EXTENT MORE RUN TO RUN VARIED UKMET/CANADIAN RUNS WEDNESDAY-FRIDAY
TENDS TO MITIGATE SMALLER SCALE ISSUES CONSISTENT WITH UNCERTAINTY
AND HAS GOOD ENSEMBLE AND NBM SUPPORT AND CONTINUITY.
BY NEXT WEEKEND THERE REMAIN SIGNIFICANT DIFFERENCES BETWEEN MODEL
GUIDANCE AND RUN TO RUN CONTINUITY ON HOW FAR SOUTH AND EAST THE
LINGERING PLAINS ENERGY WORKS INTO THE GREAT LAKES/NORTHEAST. THERE
IS ALSO UNCERTAINTY OUT WEST WITH THE EVOLUTION OF ENERGY AROUND
THE GREAT BASIN AND A BLOCKY UPPER RIDGE/HIGH REX TYPE PATTERN TO
THE NORTH. ACCORDINGLY, THE WPC BLEND HAS AGAIN TRENDED TO MORE
COMPATABLE AND RUN TO RUN CONSISTENT GEFS/ECMWF/CANADIAN ENSEMBLE
MEANS. THIS MAINTAINS MAXIMUM WPC PRODUCT CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
AMPLIFIED UPPER TROUGH/LOW ENERGIES WILL SHIFT SLOWLY FROM THE
NORTHERN PLAINS MIDWEEK TO THE EAST NEXT WEEKEND ALONG WITH
A MAIN/REFORMING PARENT SURFACE LOWS THEN MODERATE COASTAL LOW.
THERE WILL BE HIGHER ELEVATION SNOWS BACK OVER THE NORTH-CENTRAL
ROCKIES INTO MID-LATE WEEK ON THE BACKSIDE OF THE MAIN TROUGH/LOW
AS DEPICTED IN THE WPC WINTER WEATHER OUTLOOK. RAINFALL ON THE
WEST SIDE OF THE STRONG SURFACE LOW COULD BE HEAVY ACROSS EASTERN
MONTANA GIVEN UPPER-LEVEL SUPPORT. HOWEVER, THIS REGION IS NOT
PARTICULARLY SENSITIVE TO FLOODING CONCERNS, AND INSTABILITY SHOULD
BE LIMITED WRAPPING AROUND THE LOW. A WPC EXCESSIVE RAINFALL
OUTLOOK (ERO) MARGINAL RISK AREA REMAINS IN PLACE DAY 4/WEDNESDAY
FOR THIS AREA GIVEN THE POTENTIAL FOR PROTRACTED HEAVY RAIN.
MEANWHILE, AN ASSOCIATED LEAD AND WAVY/TRAILING FRONTAL SYSTEM
WILL GRADUALLY WORK DOWNSTREAM ACROSS THE CENTRAL AND EASTERN
STATES TO INTERCEPT AND POOL RETURN FLOW INSTABILITY AND MOISTURE.
THIS WILL SET THE STAGE FOR A WIDESPREAD AND GENERALLY BROAD COMMA
SHAPED AREA OF RAINFALL TO INCLUDE A THREAT FOR EXCESSIVE RAINFALL
AND STRONG TO SEVERE THUNDERSTORMS FOR AREAS NEAR THE MID-SOUTH
AND OHIO VALLEY MIDWEEK AND THE CENTRAL GULF COAST STATES TO
APPALACHIANS INTO THE SOUTHEAST THURSDAY INTO FRIDAY.
A MARGINAL RISK AND EMBEDDED SLIGHT RISK ERO IS IN PLACE FROM THE
MID-MISSISSIPPI VALLEY THROUGH THE OHIO VALLEY STATES FOR DAY
4/WEDNESDAY. THESE RISKS SHIFT TO FROM THE LOWER MISSISSIPPI
VALLEY THROUGH THE NORTHERN CENTRAL GULF COAST STATES TO THE
APPALACHIANS DAY 5/THURSDAY AS FRONTS PUSH FARTHER TOWARD THE EAST
AND NORTHEAST AND INTERACT WITH POOLING MOISTURE AND INSTABILITY.
THE STORM PREDICTION CENTER HIGHLIGHTS A BROAD AREA OF THE MIDWEST
TO MISSISSIPPI VALLEY/PARTS OF THE SOUTHERN PLAINS FOR SEVERE
WEATHER POTENTIAL INTO MIDWEEK. A FAVORABLE PATTERN WILL CONTINUE
FOR RAIN AND THUNDERSTORMS ACROSS THE SOUTHEAST WITH THE TRAILING
COLD FRONT AND BROADLY ACROSS THE EAST NEXT WEEKEND. DOWNSTREAM
ENERGY TRACK MAY ALSO LEAD TO A MODERATE NEW ENGLAND COASTAL LOW.
EXPECT MUCH COOLER THAN NORMAL TEMPERATURES FOR PARTS OF THE WEST
WEDNESDAY/THURSDAY UNDER UPPER TROUGHING. MEANWHILE, MEAN UPPER
RIDGING WILL FAVOR QUITE WARM TEMPERATURES FROM THE SOUTH THROUGH
THE APPALACHIANS/MID- ATLANTIC TO THREATEN RECORD SEASONAL VALUES.
90S ARE FORECAST ACROSS THE SOUTHERN TIER, WITH POTENTIAL FOR SOUTH
TEXAS EXCESSIVE HEAT WITH TEMPERATURES OVER 100F AND HIGHER HEAT
INDICES. TEMPERATURES BROADLY COOL LATER WEEK INTO NEXT WEEKEND.
SCHICHTEL
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
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