885
FXUS02 KWBC 241801
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
201 PM EDT SUN SEP 24 2023
VALID 12Z WED SEP 27 2023 - 12Z SUN OCT 01 2023
..OVERVIEW
THE FLOW PATTERN OF AN UPPER TROUGH SPREADING ACROSS THE WEST AND
CLOSED HIGH CENTERED OVER QUEBEC BECOMES INCREASINGLY AMPLIFIED
THROUGH THE LATTER HALF OF THIS WEEK WITH RIDGING EXTENDING OVER
THE EAST-CENTRAL CONUS AND TROUGHING ALONG OR JUST OFF THE EASTERN
SEABOARD THIS WEEKEND. EXPECT RAINFALL TO SHIFT INLAND FROM THE
PACIFIC NORTHWEST WITH HIGH ELEVATION SNOW FOR THE NORTHERN
ROCKIES THIS WEEKEND. A STALLED/SLOW MOVING COLD FRONT OVER
FLORIDA BRINGS PROLONGED WET WEATHER AND A BLOCKED LOW OVER THE
MIDWEST SHOULD BRING WET WEATHER TO THE OHIO VALLEY WEDNESDAY TO
FRIDAY.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE TIMING AND AMPLITUDE OF THE DIGGING TROUGH FROM THE NORTHWEST
TO AN EITHER SHARP TROUGH OR CLOSED LOW OVER THE GREAT BASIN BY
THIS WEEKEND IS IN DECENT AGREEMENT AMONG GLOBAL DETERMINISTIC
GUIDANCE WHICH FOR THE BULK OF THE BLEND DAYS 3-6. THE GFS AND CMC
HAVE BEEN MORE CLOSED WITH THE LOW AND FARTHER WEST/INTO
CALIFORNIA THIS WEEKEND THAN THE ECMWF WHICH IS MORE OPEN AND MORE
PROGRESSIVE OVER THE GREAT BASIN. THE 06Z GEFS IS ALSO FARTHER
WEST WITH A TROUGH/LOW THAN THE ECENS, SO MORE RELIANCE WENT TO
THE 06Z GEFS BY DAY 7 THAN THE 00Z ECENS. QPF GRIDS ARE A BLEND OF
THE 13Z NBM WITH A SELECTION OF THE ECMWF/GFS/CMC/UKMET THROUGH
DAY 5, AND THE ECMWF/GFS/CMC THEREAFTER.
..WEATHER/HAZARDS HIGHLIGHTS
A STALLED FRONT OVER THE FLORIDA PENINSULA THROUGH MUCH OF THIS
WEEK WILL BRING PERIODIC HEAVY RAINS. ENOUGH GUIDANCE AGREEMENT ON
HEAVY RAINFALL IN AND NEAR NORTHERN FL AND SOUTHERN GA REMAINS TO
MAINTAIN A MARGINAL RISK THERE FOR DAY 4/WEDNESDAY INTO THURSDAY
MORNING. THE LATEST CONSENSUS SHIFT THE HEAVIER RAINFALL FOCUS
EAST OF FLORIDA ON THURSDAY.
A SERIES OF EARLY SEASON STORMS THAT DIG A TROUGH/CLOSE A LOW OVER
THE NORTHERN CA/NV BORDER BY THIS WEEKEND WILL SHIFT ACTIVE
WEATHER FROM THE PACIFIC NORTHWEST THROUGH THE GREAT
BASIN/NORTHERN ROCKIES, AND NORTHERN HIGH PLAINS MIDWEEK THROUGH
THIS WEEKEND. RATES WILL GENERALLY BE LIGHT TO MODERATE, SO NO
EXCESSIVE RAINFALL AREAS ARE NEEDED ON DAYS 4 OR 5. SNOW AT HIGHER
ELEVATION BECOMES INCREASINGLY FAVORED WITH TIME ACROSS THE
NORTHERN ROCKIES AS THE UPPER LEVEL TROUGH STRENGTHENS.
INCREASED RIDGING OVER THE CENTER OF THE COUNTRY AND TROUGHING
ACROSS THE WEST, WILL SLOWLY SHIFT TEMPERATURES OF 10 TO 15
DEGREES ABOVE NORMAL EAST ACROSS THE CENTRAL PLAINS THROUGH THE
GREAT LAKES WITH TEMPERATURES BELOW NORMAL EXPANDING FROM THE
NORTHWEST TO ACROSS THE WEST. BELOW NORMAL TEMPERATURES OVER THE
MID-ATLANTIC STATES CAN BE EXPECTED INTO FRIDAY BEFORE MODERATING
ON APPROACH OF THE RIDGE AXIS (BUT PERHAPS STAYING BELOW NORMAL
UNDER TROUGH ALONG THE EASTERN SEABOARD).
JACKSON/ROTH
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page