250
FXUS02 KWBC 191901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT FRI MAY 19 2023
VALID 12Z MON MAY 22 2023 - 12Z FRI MAY 26 2023
...HEAVY THREAT POSSIBLE LATE NEXT WEEK FROM NORTHEASTERN FLORIDA
TO PORTIONS OF THE SOUTHEASTERN U.S...
..PATTERN OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS AND ENSEMBLES OFFER REASONABLY GOOD AGREEMENT FOR AN UPPER
RIDGE TO EDGE EVER SO SLIGHTLY EAST INTO THE HIGH PLAINS NEXT WEEK
AS AN UPPER TROUGH ALONG THE EAST COAST LIFTS AND RETREATS INTO
THE CANADIAN MARITIMES. AS THE TROUGH LIFTS, ENSEMBLE MEANS FROM
THE GEFS, EC MEAN, AND CMC GENERALLY SHOW GOOD AGREEMENT THAT A
PIECE OF THE VORTICITY ASSOCIATED WITH THE TROUGH WILL BREAK OFF
TO THE WEST OR NORTHWEST OF FLORIDA AS IT INTERACTS WITH THE
SLOW-MOVING FRONT ACROSS FLORIDA. THE 00Z ECMWF AGREES WELL WITH
ITS OWN ENSEMBLE MEANS REGARDING THIS INTERACTION, WHILE KEEPING
THE ENTIRE SYSTEM MOVING RATHER SLOWLY NEAR/OVER FLORIDA THROUGH
LATE NEXT WEEK. ON THE OTHER HAND, THE GFS HAS NOT SETTLED INTO A
STABLE SOLUTION FOR THIS SYSTEM SO FAR. THE 12Z RUN DID ATTEMPT
TO PUSH THE SYSTEM TOWARD THE CAROLINAS BY NEXT FRIDAY WHILE
ESTABLISHING A STRONGER HIGH PRESSURE RIDGE TO THE NORTH AND
NORTHEAST IN BETTER AGREEMENT WITH THE ECMWF. THE GEFS HAS
CONTINUED TO PREDICT A PATTERN IN AGREEMENT WITH THE ECMWF AND SO
HAS THE CMC AND CMC MEANS.
MEANWHILE, MODEL ENSEMBLES CONTINUE TO SUPPORT A SLOW-MOVING UPPER
TROUGH NEAR THE WEST COAST AND INTO THE PACIFIC NORTHWEST WITH
UNCERTAINTY IN THE TIMING AND AMPLITUDE OF THE POSSIBLE FORMATION
OF A CLOSED LOW TOWARD THE LATTER PART OF NEXT WEEK. A COMPOSITE
BLEND WAS USED TO COMPOSE THE WPC FORECAST PACKAGE BASED ON 40%
FROM THE 00Z ECMWF/EC MEAN, 20% FROM THE 00Z CMC/CMC MEAN, WITH
THE REMAINING PORTIONS BASED MAINLY ON THE 06Z GEFS MEAN. ONLY
MINIMAL GFS WAS USED IN THIS FORECAST CYCLE DUE TO COMPATIBILITY
WITH THE REST OF THE GUIDANCE FROM DAY 5 ONWARD. THIS OVERALL
SOLUTION MAINTAINS BROADLY GOOD WPC PRODUCT CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
A SLOW-MOVING/SEPARATED SOUTHEAST U.S. UPPER TROUGH POSITION AND
ASSOCIATED SURFACE FEATURE PROXIMITY SHOULD FOCUS MODERATE TO
LOCALLY HEAVIER RAINFALL/CONVECTION OVER PORTIONS OF THE
SOUTHEAST, BUT ESPECIALLY WITH WAVE/FRONTAL DEVELOPMENT FROM
FLORIDA TO UP THE SOUTHEAST COAST AND POTENTIALLY THE EASTERN
MID-ATLANTIC INTO MID-LATER WEEK WITH UNCERTAIN COASTAL WAVE
DEVELOPMENTS TO MONITOR. OTHERWISE, THE AFOREMENTIONED UPPER RIDGE
POSITION SHOULD SUPPORT SUMMERTIME TEMPERATURES WITH VALUES
UPWARDS TO 15-20 DEGREES ABOVE NORMAL THROUGH EARLY NEXT WEEK
SHOULD SHIFT SLOWLY EAST WITH TIME ACROSS THE NORTHERN PLAINS AND
EVENTUALLY THE MIDWEST LATER NEXT WEEK AS TEMPERED LOCALLY BY
SCATTERED AND POTENTIALLY STRONG THUNDERSTORM ACTIVITY BOTH WITH
EJECTION OF IMPULSES FROM THE WEST AND INTERACTION WITH NORTHERN
STREAM SYSTEM/FRONTAL APPROACHES FROM SOUTHERN CANADA. LOCALLY
HEAVY THUNDERSTORM ACTIVITY MAY FOCUS HEAVY LOCAL DOWNPOURS DOWN
OVER THE SOUTHERN PLAINS AS WELL WITH MOISTURE/INSTABILITY POOLING
WITH SOUTHERN STREAM IMPULSES. ABOVE TO MUCH ABOVE NORMAL
OVERNIGHT TEMPERATURES AND A PATTERN FAVORING SCATTERED TO
WIDESPREAD SHOWERS AND THUNDERSTORMS ARE ALSO EXPECTED TO LINGER
ALL NEXT WEEK OVER MUCH OF INTERIOR WEST THROUGH THE ROCKIES IN
MOISTENED FLOW CHANNELED BETWEEN WEST COAST UPPER TROUGHING AND
THE DOWNSTREAM CENTRAL U.S. UPPER RIDGE.
KONG/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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page