359
FXUS02 KWBC 182018
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
417 PM EDT THU MAY 18 2023
VALID 12Z SUN MAY 21 2023 - 12Z THU MAY 25 2023
..THREAT OF HEAVY RAIN INCREASING LATE NEXT WEEK OVER FLORIDA
...WARMER THAN AVERAGE TEMPERATURES WILL PUSH FROM THE NORTHWEST
INTO THE NORTHERN PLAINS...
..OVERVIEW
THE MEDIUM-RANGE PERIOD WILL BEGIN THIS WEEKEND WITH A LOW
PRESSURE WAVE EXITING THE GREAT LAKES AS ANOTHER WAVE EXITS THE
NEW ENGLAND COAST WHILE TAPING INTO SOME SUBTROPICAL ATLANTIC
MOISTURE. MEANWHILE, PERSISTENT RIDGING IN THE WEST WILL SHIFT
EASTWARD INTO THE NORTHERN PLAINS BY LATE NEXT WEEK AS THE NEXT
UPPER TROUGH REACHES INTO THE PACIFIC NORTHWEST. MONSOONAL
MOISTURE WILL MAKE ITS APPEARANCE OVER THE CENTRAL ROCKIES AND THE
GREAT BASIN. A LINGERING FRONT ACROSS FLORIDA WILL KEEP UNSETTLED
WEATHER THIS WEEKEND WITH SOME THREAT OF HEAVY RAIN NEAR THE EAST
COAST BUT A BETTER CHANCE OF HEAVY RAIN APPEARS TO EMERGE LATE
NEXT WEEK AS MODELS SHOW BETTER INDICATIONS THAT AN UPPER
TROUGH/LOW WILL DEVELOP OVER THE EASTERN GULF OF MEXICO AND
INTERACT WITH ANTECEDENT MOISTURE ASSOCIATED WITH THE LINGERING
FRONT OVER FLORIDA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE THIS MORNING APPEARS RATHER AGREEABLE WITH EACH
OTHER IN DEPICTING THE OVERALL EVOLUTION OF THE SYNOPTIC PATTERN
ACROSS THE U.S. THROUGH THE MEDIUM-RANGE FORECAST PERIOD. MUCH OF
THE DISAGREEMENT APPEARS TO BE CENTERED AROUND THE NEXT UPPER
TROUGH FORECAST TO DIG INTO THE PACIFIC NORTHWEST LATE NEXT WEEK.
OVER THE CENTRAL HIGH PLAINS, THE 06Z GEFS WAS FASTEST WITH THE
SURFACE TROUGH REACHING INTO THE REGION LATE NEXT WEEK, WITH THE
REST OF THE GUIDANCE BEING SLOWER. OVER THE NORTHERN HIGH PLAINS,
LATEST MODEL CONSENSUS HAS SLOWED DOWN THE NORTHEASTWARD PROGRESS
OF THE LOW PRESSURE WAVE LATE NEXT WEEK. THIS IS REFLECTED IN THE
LATEST WPC FORECAST CHARTS. ACROSS THE SOUTH AND INTO FLORIDA,
MODELS ARE INDICATING A PIECE OF THE UPPER TROUGH ASSOCIATED WITH
THE LINGERING FRONT WILL BREAK OFF LATE NEXT WEEK OVER THE EASTERN
GILF OF MEXICO. THE GFS FAVORS MORE ENERGY TO SLIDE INTO THE
TROUGH FROM THE NORTHWEST WHEREAS THE ECMWF FAVORS A STRONGER
INFLUENCE FROM ENERGY BREAKING OFF FROM THE TROUGH LIFTING OUT OF
NEW ENGLAND.
..WEATHER/HAZARDS HIGHLIGHTS
BY SUNDAY A COLD FRONT WILL HAVE CLEARED MOST OF THE EASTERN U.S.,
WITH THE EXCEPTION OF THE SOUTHEAST, PARTICULARLY SOUTHERN GEORGIA
INTO FLORIDA. THE FRONT PLUS ABOVE AVERAGE/AMPLE MOISTURE LEVELS
COULD SPARK THUNDERSTORMS WITH LOCALLY HIGH RAIN RATES. IT
APPEARS THAT THE CONSENSUS IS FOR MUCH OF THE HEAVY RAIN TO BE
OFFSHORE THIS WEEKEND ALTHOUGH THE GFS FAVORS A BAND OF HEAVY RAIN
SLIDING ACROSS THE SOUTHEAST BEHIND THE STATIONARY FRONT EARLY
NEXT WEEK. IT APPEARS THAT THE GENERAL UPPER-LEVEL FORCING WILL
BE OFFSHORE TO SUPPORT A FRONTAL WAVE WELL OFFSORE. TOWARD THE
LATTER PORTION OF NEXT WEEK, LATEST GUIDANCE INDICATES A TENDENCY
FOR AN UPPER-LEVEL TROUGH TO DEVELOP OVER THE EASTERN GULF OF
MEXICO AND POSSIBLY TRYING TO CLOSE OFF OVER FLORIDA BY LATE WEEK.
INTERACTION WITH ANTECEDENT MOISTURE ASSOCIATED WITH THE NEARBY
STATIONARY FRONT WOULD DESTABILIZE THE ATMOSPHERE AND DEEPEN
TROPICAL MOISTURE, LEADING TO AN INCREASING CHANCE OF HEAVY
RAINFALL OVER FLORIDA LATE NEXT WEEK.
TEMPERATURES IN THE PACIFIC NORTHWEST WILL HAVE RETURNED CLOSER TO
NORMAL BY EARLY NEXT WEEK, BUT FOR INTERIOR AREAS LIKE THE GREAT
BASIN, TEMPERATURES OF 15-20F ABOVE AVERAGE WILL BE COMMON THROUGH
SUNDAY UNDER THE INFLUENCE OF THE UPPER RIDGE/HIGH. TEMPERATURES
IN THE 50S AND 60S COULD BREAK RECORDS FOR WARM MINIMUM
TEMPERATURES ACROSS WIDESPREAD AREAS OF THE WEST ESPECIALLY
SUNDAY. EVEN WITH THE ARRIVAL OF COOLER AIR ASSOCIATED WITH THE
NEXT UPPER TROUGH, TEMPERATURES ARE FORECAST TO REMAIN ABOVE
NORMAL INTO LATE WEEK ACROSS THE NORTHWEST. MEANWHILE, THE WARMTH
SHOULD SHIFT EAST WITH TIME INTO THE NORTHERN PLAINS AND
EVENTUALLY THE MIDWEST (IN MODERATED FORM) THROUGH THE WEEK, WITH
SOME ABOVE NORMAL TEMPERATURES REMAINING IN CALIFORNIA/NEVADA
THOUGH. NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES ARE POSSIBLE
ACROSS THE SOUTHERN TIER WITH POST-FRONTAL COOLER AIR.
KONG/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
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, MON-THU, MAY 22-MAY
25.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS, THE
NORTHERN ROCKIES, AND THE NORTHERN
GREAT BASIN.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE CENTRAL
ROCKIES, THE UPPER MISSISSIPPI
VALLEY, THE SOUTHERN PLAINS, THE NORTHERN ROCKIES, AND THE
NORTHERN GREAT BASIN.
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE
CENTRAL GREAT BASIN, THE NORTHERN
PLAINS, THE NORTHERN ROCKIES, THE SOUTHERN ROCKIES, THE NORTHERN
GREAT BASIN, THE UPPER MISSISSIPPI
VALLEY, AND THE SOUTHWEST.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL
GREAT BASIN, THE NORTHERN PLAINS,
THE NORTHERN ROCKIES, CALIFORNIA, THE NORTHERN GREAT BASIN, AND
THE PACIFIC NORTHWEST, SUN-MON, MAY
21-MAY 22.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL
GREAT BASIN, THE PACIFIC NORTHWEST,
THE NORTHERN ROCKIES, AND THE NORTHERN GREAT BASIN, SUN, MAY 21.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY AND THE NORTHERN
PLAINS, MON-TUE, MAY 22-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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