287
FXUS02 KWBC 181901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 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 THIS WEEKEND WITH A LOW PRESSURE WAVE
EXITING THE GREAT LAKES AS ANOTHER WAVE EXITS THE NEW ENGLAND
WHILE TAPING INTO SOME SUBTROPICAL ATLANTIC MOISTURE. MEANWHILE,
PERSISTENT RIDGING IN THE WEST WILL BE SHIFTED 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 BE LATE NEXT WEEK AS MODELS
SHOW BETTER INDICATIONS OF 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 INTO
THE LATEST WPC FORECAST CHARTS.
..WEATHER/HAZARDS HIGHLIGHTS
BY SUNDAY A COLD FRONT WILL HAVE CLEARED MOST OF THE EAST, WITH
THE EXCEPTION OF THE SOUTHEAST, PARTICULARLY SOUTHERN GEORGIA INTO
FLORIDA. THE FRONT PLUS ABOVE AVERAGE/AMPLE MOISTURE LEVELS COULD
SPARK THUNDERSTORMS WITH HIGH RAIN RATES. MARGINAL RISKS ARE
PLANNED FOR THE DAY 4 AND 5 (SUNDAY AND MONDAY) EROS NEAR THE
TRACK OF THIS FRONT, FIRST FOR SOUTHERN GEORGIA AND NORTHERN
FLORIDA ON SUNDAY AND FOR MUCH OF THE FLORIDA PENINSULA ON MONDAY.
THOUGH FLASH FLOOD GUIDANCE IS RELATIVELY HIGH, HIGH RAIN RATES
COULD OVERWHELM PARTICULARLY URBAN AREAS WITH POTENTIAL FOR FLASH
FLOODING. MEANWHILE, SCATTERED SHOWERS AND THUNDERSTORMS ARE ALSO
POSSIBLE IN THE WEST AT TIMES INTO NEXT WEEK ESPECIALLY IN THE
AFTERNOONS/EVENINGS WITH A COMMON DIURNAL CYCLE, AS A MONSOON-LIKE
PATTERN SETS UP WITH ANOMALOUSLY HIGH MOISTURE REMAINING OVER A
LARGE PORTION OF THE WESTERN U.S. AS TROUGHING EDGES IN. ONE AREA
THAT CONVECTION MAY BE MOST COMMON IS ACROSS THE SOUTHERN HIGH
PLAINS THROUGH MUCH OF THE WEEK. CHANCES FOR SHOWERS AND
THUNDERSTORMS WILL INCREASE ACROSS MUCH OF THE PLAINS BY
TUESDAY-THURSDAY AHEAD OF THE UPPER TROUGH AND A FRONTAL SYSTEM.
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 AND PERIODS
OF RAIN AND CLOUDS WITH 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.
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
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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