063
FXUS02 KWBC 081836
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT WED MAY 8 2024
VALID 12Z SAT MAY 11 2024 - 12Z WED MAY 15 2024
..EMERGING TEXAS/GULF COAST/SOUTHEAST HEAVY RAINFALL THREAT
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE CONTINUES TO SHOW PRETTY GOOD AGREEMENT THAT MEAN
TROUGHING WILL LINGER OVER THE GREAT LAKES/EASTERN U.S. INTO EARLY
NEXT WEEK AS A BLOCKY PATTERN OUT WEST TAKES SOME TIME TO DE-
AMPLIFY. BY EARLY NEXT WEEK, SHORTWAVE ENERGY INTO WESTERN CANADA
WILL AMPLIFY OVER THE NORTHWESTERN U.S. ALLOWING A CLOSED LOW OVER
THE GREAT BASIN TO SHIFT EASTWARD INTO THE PLAINS/MIDWEST MONDAY-
WEDNESDAY. THIS SHOULD ALSO HELP PUSH TROUGHING OVER THE EAST OUT
AND UPPER RIDGING TO BUILD ACROSS THE SOUTHEAST. ADDITIONAL
SHORTWAVE ENERGY MAY MOVE INTO THE SOUTHWEST LATE PERIOD AS WELL.
OVERALL, THE LATEST MODELS AND ENSEMBLES SHOW GOOD AGREEMENT ON THE
LARGE SCALE PATTERN, BUT PLENTY OF UNCERTAINTY IN THE TIMING AND
DETAILS OF INDIVIDUAL SYSTEMS. THE DIFFERENCES IN THE CENTRAL U.S.
SHORTWAVE IN PARTICULAR COULD HAVE BIGGER IMPLICATIONS ON HEAVY
RAINFALL ACROSS PARTS OF THE SOUTHERN PLAINS INTO THE GULF
COAST/SOUTHEAST THIS WEEKEND AND INTO NEXT WEEK, INCLUDING AREAS
THAT HAVE BEEN VERY WET IN THE PAST WEEK. SO THESE AREAS MAY BE
MORE SENSITIVE THAN NORMAL TO SMALLER CHANGES IN THE
PATTERN/DETAILS.
DESPITE THE DIFFERENCES, IT SEEMED THAT A GENERAL MODEL COMPROMISE
WORKED WELL AS A STARTING POINT AND OFFERED THE BEST CONTINUITY
WITH THE PREVIOUS WPC FORECAST. FOR DAYS 3-5, WAS ABLE TO USE AN
EQUAL BLEND OF THE DETERMINISTIC SOLUTIONS, INCORPORATING
INCREASING AMOUNTS OF THE ENSEMBLE MEANS INTO THE BLEND FOR DAYS
6-7 TO MITIGATE THE SMALLER SCALE DETAILS THAT ARE IMPOSSIBLE TO
RESOLVE AT THESE LONGER TIME SCALES.
..WEATHER/HAZARDS HIGHLIGHTS
MODERATE RAINFALL WILL LINGER THIS WEEKEND OVER THE NORTHEAST WITH
WRAPBACK MOISTURE AND UPPER TROUGH SUPPORT AS DOWNSTREAM ENERGY
TRANSFERENCE LEADS TO COASTAL LOW GENESIS, BUT DETAILS REMAIN
UNCHARACTERISTICALLY UNCERTAIN EVEN AS WE ENTER SHORT RANGE TIME
FRAMES. UPSTREAM NORTHERN STREAM SYSTEMS WILL THEN PERIODICALLY
OFFER BOUTS OF MAINLY LIGHTER RAINS FROM THE NORTH-CENTRAL U.S. TO
THE GREAT LAKES/NORTHEAST THIS WEEKEND TO NEXT MIDWEEK, ALBEIT
ALSO WITH UNCERTAINTY IN FOCUS/TIMING, BUT WITH LIMITED IMPACT.
MEANWHILE TO THE SOUTH, A COOLING/SLOWING TRAILING FRONT ALONG
WITH A REINFORCING FRONT AND UPPER SHORTWAVES ARE EXPECTED TO
PERIODICALLY FOCUS PRECIPITATION FROM THE SOUTHERN ROCKIES/PLAINS
OUT THROUGH THE GULF OF MEXICO AND GULF COAST/FLORIDA THIS WEEKEND
THROUGH EARLY-MID NEXT WEEK. A GROWING BUT STILL NOT SOLIDIFIED
GUIDANCE SIGNAL OFFERS SUPPORT FOR MOISTURE TO INCREASE ALONG THE
GULF COAST AND VICINITY AHEAD OF THE RETURNING WARM FRONT. HEAVY
RAIN MAY WORK INLAND OVER TIME AS THE FRONT EDGES NORTHWARD. THE
WPC DAY 5/SUNDAY INTO MONDAY EXCESSIVE RAINFALL OUTLOOK UPDATE THIS
AFTERNOON EXPANDED THE PREVIOUS MARGINAL RISK AREA SIGNIFICANTLY
NORTHWARD INTO EASTERN TEXAS TO FAR SOUTHERN OKLAHOMA. GIVEN
SOIL/STREAMFLOW SENSITIVITIES ACROSS ESPECIALLY SOUTHEAST TEXAS,
ALSO EXPANDED THE SLIGHT RISK FARTHER NORTH. HEAVY RAIN AND A
THREAT OF RUNOFF ISSUES MAY ALSO SPREAD THROUGH THE CENTRAL GULF
COAST TO THE SOUTHEAST EARLY-MID NEXT WEEK TO MONITOR.
SANTORELLI/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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