989
FXUS02 KWBC 191958
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
357 PM EDT FRI MAY 19 2023
VALID 12Z MON MAY 22 2023 - 12Z FRI MAY 26 2023
...HEAVY RAIN 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 THE VORTICITY 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, ENSEMBLE MEANS 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 INCOMPATIBILITY
WITH THE REST OF THE GUIDANCE FROM DAY 5 ONWARD. THIS OVERALL
SOLUTION MAINTAINS BROADLY GOOD WPC PRODUCT CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
GIVEN THE CONSENSUS AMONG LATEST MODEL GUIDANCE IN SUPPORT OF A
SLOW-MOVING/SEPARATED UPPER TROUGH OVER SOUTHEAST U.S./FLORIDA
LATE NEXT WEEK, HEAVY RAIN IS PROPOSED LATE NEXT WEEK FROM
NORTHEASTERN FLORIDA TO PORTIONS OF THE SOUTHEASTERN U.S. WITH A
SURFACE LOW FORECAST TO BE CENTERED NEAR THE EAST COAST OF
FLORIDA, POSSIBLY LOSING FRONTAL CHARACTERISTICS SLOWLY WITH TIME.
STRONG EASTERLY ONSHORE FLOW CAN BE EXPECTED TO SET UP NORTH OF
THE SURFACE LOW UNDER SUCH SCENARIO. THERE COULD ALSO BE COASTAL
WAVE DEVELOPMENTS FARTHER UP THE EAST COAST BUT WITH PLENTY OF
UNCERTAINTY. 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
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, TUE, MAY 23 AND
FRI, MAY 26.
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, TUE, MAY 23.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY, THE SOUTHERN
PLAINS, THE NORTHERN ROCKIES, AND THE NORTHERN GREAT BASIN.
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE
UPPER MISSISSIPPI VALLEY, THE CENTRAL
GREAT BASIN, THE NORTHERN ROCKIES, AND THE NORTHERN GREAT BASIN.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL
PLAINS, THE CENTRAL GREAT BASIN,
THE NORTHERN PLAINS, THE NORTHERN GREAT BASIN, CALIFORNIA, AND THE
PACIFIC NORTHWEST, MON, MAY 22.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY AND THE NORTHERN
PLAINS, TUE, MAY 23.
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
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