407
FXUS02 KWBC 091901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 PM EDT SUN OCT 09 2022
VALID 12Z WED OCT 12 2022 - 12Z SUN OCT 16 2022
...HEAVY RAIN AND FLOODING ARE POSSIBLE THURSDAY-FRIDAY IN THE
NORTHEAST AHEAD OF A STRONG COLD FRONT...
..PATTERN OVERVIEW
A HIGHLY AMPLIFIED AND SOMEWHAT STAGNANT UPPER LEVEL PATTERN WILL
BE IN PLACE LATE WEEK INTO NEXT WEEKEND, AS AN UPPER HIGH AND
RIDGE HOVER FROM THE EASTERN PACIFIC INTO THE NORTHWEST WITH A
WEAK UPPER LOW FARTHER SOUTH, AND A DEEP TROUGH FROM THE PLAINS TO
THE EAST COAST. TWO OR THREE WELL DEFINED COLD FRONTS ARE EXPECTED
TO PASS FROM THE NORTHERN PLAINS TO THE EASTERN U.S., THUS
REINFORCING THE COOL AND AUTUMNAL AIRMASS WITH GENERALLY BELOW
NORMAL TEMPERATURES CONTINUING. AHEAD OF THE FIRST COLD FRONT,
GULF MOISTURE STREAMING IN WILL LEAD TO WIDESPREAD RAIN TREKKING
ACROSS THE EASTERN HALF OF THE U.S. WEDNESDAY-FRIDAY. RAIN IS
FORECAST TO BE PARTICULARLY HEAVY IN THE NORTHEAST AROUND
THURSDAY-FRIDAY AS THE MID-UPPER LEVEL TROUGH BECOMES NEGATIVELY
TILTED, WITH GUSTY WINDS ALSO A POTENTIAL CONCERN. BEHIND THE
INITIAL FRONT, LAKE EFFECT/ENHANCED PRECIPITATION IS POSSIBLE
DOWNWIND OF THE GREAT LAKES. THE WEST IS FORECAST TO REMAIN WARMER
THAN NORMAL AND MAINLY DRY UNDER THE INFLUENCE OF THE UPPER RIDGE,
BUT MOISTURE COULD RETURN TO THE SOUTHWEST AND SOUTHERN PLAINS
NEXT WEEKEND.
..MODEL AND PREDICTABILITY ASSESSMENT
BY DAY 3/WEDNESDAY, MODEL GUIDANCE CONTINUES TO SHOW GOOD
AGREEMENT THAT A POTENT TROUGH WILL BE IN PLACE ACROSS CENTRAL
NORTH AMERICA, AND ITS AXIS SHOULD SHIFT SLOWLY EASTWARD
THURSDAY-FRIDAY AS ADDITIONAL ENERGY SPILLS INTO THE TROUGH,
ROUNDING ITS SHAPE AND PRODUCING A CLOSED LOW. THERE REMAINS SOME
NORTH-SOUTH UNCERTAINTY IN THE EXACT CENTROID OF THE UPPER LOW,
BUT REGARDLESS ANOMALOUSLY DEEP TROUGHING WILL BE WELL ESTABLISHED
OVER THE EAST-CENTRAL CONUS AS SHOWN BY THE FULL ARRAY OF MODELS.
BY THE WEEKEND, THE TROUGH IS LIKELY TO REMAIN IN PLACE, BUT ITS
EVOLUTION APPEARS MORE QUESTIONABLE AS SOME ENERGY MAY LIFT WHILE
ADDITIONAL ENERGY DIGS INTO THE WESTERN SIDE. THE 00Z/06Z GFS
CONTINUES THE CLOSED LOW THROUGH SATURDAY WHILE THE 00Z ECMWF
TEMPORARILY OPENS UP THE LOW BEFORE THE EXTRA ENERGY SPILLS IN
FROM THE NORTH. THE EXACT AXIS OF THE TROUGHING WILL AFFECT
FRONTAL TIMING AT THE SURFACE AND THERE COULD BE SOME ADDITIONAL
SHIFTS TO THE FRONTAL POSITION OVER THE NEXT FEW DAYS. REGARDLESS
OF THESE DIFFERENCES, A MULTI-MODEL AND ENSEMBLE BLEND SUFFICED
FOR THIS STRONG TROUGH PATTERN.
PERHAPS A BIT MORE UNCERTAIN IS THE POSITION OF THE WEAKER UPPER
LOW FEATURE NEAR SOUTHERN CALIFORNIA. FOR THE 00/06Z MODEL CYCLE,
THE GFS AND CMC WERE ON THE EASTERN SIDE OF THE GUIDANCE, WHILE
THE UKMET AND ECMWF WERE WEST. GFS RUNS TRENDED WEST WITH TIME
SINCE THE PREVIOUS MODEL CYCLE, AND GEFS MEMBERS SHOWED SOME
WEST-EAST SPREAD BUT EVEN THE GEFS MEAN WAS FARTHER WEST THAN THE
DETERMINISTIC GUIDANCE. HOWEVER, CONTINUITY WITH THE UPPER LOW
POSITION WAS FARTHER EAST, SO WITH THIS VARIABILITY OPTED TO GO
WITH A MIDDLE GROUND BUT LEANING WEST SOLUTION FAVORING THE ECMWF
(WHICH WAS A BIT EAST OF THE UKMET) AND THE EC ENSEMBLE MEAN FOR
THIS FEATURE. THE NEWER 12Z ECMWF CAME IN EAST A BIT OF ITS
PREVIOUS RUN. THE DIFFERENCES WITH THE UPPER LOW ARE SOMEWHAT
SMALL BUT DO BECOME SOMEWHAT IMPACTFUL FOR THE TIMING OF ITS
GRADUAL SHIFT EASTWARD THAT EVENTUALLY COULD BRING A SOURCE OF
LIFT FOR RAIN ACROSS THE SOUTHWEST INTO THE SOUTHERN PLAINS.
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
THE FIRST STRONG COLD FRONT AND THE ASSOCIATED UPPER TROUGH WILL
BRING A RETURN TO WIDESPREAD SHOWERS AND STORMS FROM THE CENTRAL
GULF COAST TO THE OHIO VALLEY AND GREAT LAKES ON WEDNESDAY AS
DEEPER MOISTURE IS ADVECTED NORTHWARD. THE COMBINATION OF
INCREASING INSTABILITY AND FAVORABLE KINEMATIC PARAMETERS IN THE
WARM SECTOR MAY LEAD TO SOME STRONG TO SEVERE THUNDERSTORMS IN
TERMS OF HIGH WINDS ACROSS SOUTHERN PARTS OF THE GREAT LAKES
REGION INTO THE OHIO/TENNESSEE VALLEYS ON WEDNESDAY, AND THEN
PERHAPS ACROSS PORTIONS OF THE NORTHEAST ON THURSDAY, ALTHOUGH
CONFIDENCE IS STILL LIMITED ON EXACTLY WHERE THESE STORMS COULD
DEVELOP. RAINFALL AMOUNTS ARE LIKELY TO BE HIGHEST IN THE INTERIOR
NORTHEAST THURSDAY AND CONTINUING INTO FRIDAY AS DEEPER ATLANTIC
MOISTURE IS ADVECTED TOWARDS THE NORTHERN APPALACHIANS WITH AN
INCREASING LOW LEVEL JET. A SLIGHT RISK AREA REMAINS IN PLACE IN
WPC'S EXPERIMENTAL DAY 5 EXCESSIVE RAINFALL OUTLOOK FOR THIS
REGION. TERRAIN COULD ENHANCE RAIN TOTALS IN AREAS LIKE THE
ADIRONDACKS AND WHITE AND GREEN MOUNTAINS, BUT LOWER ELEVATIONS
COULD SEE HEAVY RAINFALL AS WELL AND GENERALLY HAVE LOWER FLASH
FLOOD GUIDANCE, LEADING TO A BROAD RISK FOR FLASH FLOODING.
ELSEWHERE, LAKE ENHANCED SHOWERS (MAINLY RAIN BUT COULD BE IN THE
FORM OF SNOW IN UPPER MICHIGAN/FAR NORTHERN WISCONSIN) ARE LIKELY
FOR THE THURSDAY THROUGH SATURDAY TIME PERIOD, AND SHOWERS COULD
BECOME MORE WIDESPREAD WITH ANOTHER FRONTAL SYSTEM BY SUNDAY. MOST
OF THE WEST SHOULD REMAIN DRY THROUGH THE LATTER PART OF THE
WORKWEEK WITH PERHAPS A FEW ISOLATED SHOWERS/STORMS OVER ARIZONA
AND NEW MEXICO INTO TEXAS, WITH COVERAGE POSSIBLY INCREASING NEXT
WEEKEND.
MUCH OF THE NORTHWESTERN U.S. AND CALIFORNIA SHOULD HAVE ABOVE
NORMAL TEMPERATURES EACH DAY WITH THE UPPER RIDGE REMAINING NEARLY
ANCHORED IN PLACE NEAR THE COAST, AND A BRIEF WARM-UP IS LIKELY
FROM THE ARKLATEX REGION TO THE OHIO VALLEY AHEAD OF THE FRONT ON
WEDNESDAY. THIS WILL LIKELY BE FOLLOWED BY HIGHS ABOUT 5-15
DEGREES BELOW AVERAGE TO CLOSE OUT THE WORKWEEK AND GOING INTO
NEXT WEEKEND FROM THE UPPER MIDWEST TO THE OHIO VALLEY AND GREAT
LAKES, WITH HIGHS ONLY IN THE 40S AND 50S FOR MOST OF THESE AREAS.
TATE/HAMRICK
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