899
FXUS02 KWBC 051901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SUN NOV 05 2023
VALID 12Z WED NOV 08 2023 - 12Z SUN NOV 12 2023
..OVERVIEW
THE UPPER FLOW PATTERN ACROSS THE CONTIGUOUS U.S. DURING THE
LATTER PART OF THIS WEEK INTO NEXT WEEKEND LOOKS TO BE FAIRLY
ZONAL AND PROGRESSIVE FROM THE MULTI-DAY MEAN PERSPECTIVE, BUT
MULTIPLE EMBEDDED SHORTWAVES WILL BE IMPACTFUL IN SPINNING UP LOW
PRESSURE/FRONTAL SYSTEMS. AS THE LEADING SYSTEM IN THE SERIES
PULLS AWAY FROM THE NORTHEAST ON WEDNESDAY, THE NEXT SYSTEM OF
CONCERN IS A POSITIVELY TILTED SHORTWAVE EMERGING FROM THE WEST
AND EVENTUALLY REINFORCED BY SOME CANADIAN FLOW. EASTWARD
PROGRESSION OF THE UPPER TROUGH AND ASSOCIATED WAVY FRONT DURING
THE LATTER HALF OF THE WEEK WILL GRADUALLY SUPPRESS WHAT STARTS AS
A WIDESPREAD AREA OF ABOVE AVERAGE TEMPERATURES WHILE BRINGING
PRECIPITATION OF VARYING INTENSITY TO PARTS OF THE SOUTHERN AND
EASTERN U.S. MEANWHILE, THE WEST LOOKS TO HAVE A BREAK IN
PRECIPITATION AROUND MIDWEEK, ASIDE FROM SNOW IN THE CENTRAL
ROCKIES. THEN AN APPROACHING PACIFIC SHORTWAVE AND FRONTAL SYSTEM
SHOULD INCREASE RAIN/SNOW CHANCES LATE THIS WEEK WITH THE
AMPLIFYING UPPER TROUGH MOVING INLAND BY THE WEEKEND, FOLLOWED BY
A LARGER SCALE EASTERN PACIFIC UPPER TROUGH THAT MAY GENERATE
ADDITIONAL PRECIPITATION OVER THE PACIFIC NORTHWEST DURING THE
WEEKEND.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
LATEST MODEL AND ENSEMBLE RUNS CONTINUE TO SHOW CONSIDERABLE
SPREAD FOR DETAILS OF THE FORECAST. THESE INCLUDE ONGOING ISSUES
WITH LOW PRESSURE/FRONTS REACHING THE NORTHEAST BY THURSDAY
(RELATING TO DETAILS OF WITHIN THE SUPPORTING UPPER TROUGH),
DIFFERENCES FOR WHAT BECOMES OF SHORTWAVE ENERGY ENTERING THE WEST
BY FRIDAY ALONG WITH ENERGY ON THE BACK SIDE OF THE DOWNSTREAM
TROUGH, AND PROGRESSION OF THE LEADING SIDE OF EASTERN PACIFIC
TROUGHING THAT BEGINS TO AFFECT THE NORTHWEST NEXT WEEKEND.
MODELS STILL VARY CONSIDERABLY FOR THE THURSDAY SYSTEM OVER THE
NORTHEAST. THE GFS/GEFS GENERALLY STRAY ON THEIR OWN WITH A
FARTHER NORTH TRACK OF EASTERN GREAT LAKES LOW PRESSURE AFTER
EARLY THURSDAY, PUSHING A DEFINED FRONTAL BOUNDARY THROUGH NEW
ENGLAND IN CONTRAST TO MOST OTHER GUIDANCE THAT TAKES A MORE
SUPPRESSED TRACK. THE 00Z ECMWF LOOKS MORE AGGRESSIVE THAN OTHER
GUIDANCE IN PUSHING SHORTWAVE ENERGY THROUGH AN UPPER RIDGE
CROSSING NEW ENGLAND, BUT THE 12Z UKMET IS NOT FAR BEHIND IN THAT
REGARD AND BOTH END UP WITH VERY SIMILAR SURFACE FORECASTS THAT
ARE ON THE MOST SUPPRESSED SIDE OF THE ENVELOPE. CMC/CMCENS RUNS
HAVE GENERALLY BEEN BETWEEN THESE EXTREMES. PREFERENCE REMAINS
CLOSE TO A COMPROMISE APPROACH WHILE AWAITING BETTER CLUSTERING.
SMALL SCALE NATURE OF INDIVIDUAL IMPULSES TRACKING OUT OF THE WEST
KEEPS PREDICTABILITY LOW FOR SPECIFICS OF WAVES ALONG THE TRAILING
COLD FRONT.
FARTHER WEST, MOST GUIDANCE HAS BEEN RECENTLY TRENDING MORE
DIFFUSE WITH THE UPPER TROUGH MOVING INTO THE WEST. LATEST GFS
RUNS HAVE BEEN A BIT ON THE FAST SIDE WITH EASTWARD PROGRESSION AS
THE TROUGH ARRIVES INTO THE NORTHWEST. AS THE TROUGH CONTINUES
ACROSS THE WEST, THERE IS SOME TIMING DEPENDENCE ON FLOW ON THE
WESTERN SIDE OF THE DOWNSTREAM TROUGH. THE GFS REMAINS ON THE FAST
SIDE AS IT IS MOST EAGER TO EJECT THE TROUGH TO THE EAST, WHILE
THE 00Z ECMWF STRAYS SLOW DUE TO HOLDING UPPER TROUGHING OVER THE
NORTHERN PLAINS/UPPER MIDWEST LONGER THAN SUPPORTED BY OTHER
GUIDANCE. THE NEW 12Z ECMWF HAS TRENDED AWAY FROM THE EXTREME
ASPECTS OF THE 00Z VERSION. THE NEXT UPPER TROUGH REACHING THE
EASTERN PACIFIC IS A LITTLE FASTER IN THE 00Z ECMWF/ECENS MEAN
COMPARED TO MOST OTHER SOLUTIONS BY VARYING DEGREES. THE GEFS MEAN
HAD BEEN SLOWEST BY A NARROW MARGIN BUT THE NEW 12Z CMC HAS NOW
CLAIMED THAT ROLE. MEANWHILE THE NEW 12Z ECMWF HAS RAISED WEST
COAST HEIGHTS NOTICEABLY BY NEXT SUNDAY.
THE UPDATED FORECAST STARTED WITH A COMPOSITE OF 00Z/06Z
OPERATIONAL RUNS EARLY IN THE PERIOD TO YIELD THE DESIRED
INTERMEDIATE SOLUTION WITHIN CURRENT SPREAD, WHILE TRANSITIONING
TO A MODEL/ENSEMBLE MEAN MIX (INCLUDING THE GEFS/ECENS/CMCENS) BY
NEXT WEEKEND TO ACCOUNT FOR STEADILY DECREASING CONFIDENCE IN
DETAILS.
..WEATHER/HAZARDS HIGHLIGHTS
AS A NOTABLE SHORTWAVE AND ITS SURFACE LOW REFLECTION TRACK EAST
THROUGH THE PLAINS WEDNESDAY INTO THE MIDWEST/GREAT LAKES AND
NORTHEAST THROUGH THE LATTER PART OF THE WEEK, PRECIPITATION IS
LIKELY BUT MODEL DIFFERENCES LEAD TO CONSIDERABLE UNCERTAINTY WITH
THE PRECIPITATION COVERAGE, AMOUNTS, AND TYPE. OVERALL THIS MAY BE
A SOMEWHAT COLDER SYSTEM, WITH PRECIPITATION IN THE FORM OF SNOW
POSSIBLE IN AREAS NEAR THE CANADIAN BORDER AND AT LEAST THE HIGHER
ELEVATIONS OF THE INTERIOR NORTHEAST, PERHAPS EVEN INTO LOWER
ELEVATIONS OF NORTHERN NEW ENGLAND. THERE IS LOW CONFIDENCE IN
SNOW LEVELS AND AMOUNTS AT THIS POINT THOUGH. LIGHT LAKE EFFECT
PRECIPITATION WILL BE POSSIBLE AFTER THIS SYSTEM PASSES. RAIN OF
VARYING INTENSITY IS POSSIBLE FARTHER SOUTHWEST ALONG THE FRONTAL
CORRIDOR, POTENTIALLY PEAKING THURSDAY IN THE SOUTH-CENTRAL CONUS.
EASTERN PACIFIC AND GULF MOISTURE ARE FORECAST TO COMBINE IN THE
VICINITY OF THE FRONT, WITH THE RIGHT ENTRANCE REGION OF THE JET
STREAM OVERHEAD. THIS COULD LEAD TO HEAVY RAINFALL CAUSING FLASH
FLOODING, SO A MARGINAL RISK IS MAINTAINED IN THE DAY 5/THURSDAY
EXCESSIVE RAINFALL OUTLOOK ACROSS PORTIONS OF THE SOUTHERN PLAINS
AND LOWER MISSISSIPPI VALLEY. THE SOUTHERN PORTION OF THE RISK
AREA SHOULD SEE THE HIGHEST INSTABILITY, WHILE FARTHER NORTH LOOKS
TO HAVE THE HIGHEST RISK OF TRAINING CONVECTION. PLUS MODEL
VARIABILITY IN THE PLACEMENT OF THE HEAVIEST AMOUNTS LEADS US TO
COVER A LARGER AREA AT THIS POINT, THAT COULD BE NARROWED WITH
TIME AS MODELS CONVERGE. THAT HAS NOT YET HAPPENED IN THE NEW 12Z
RUNS SO THE OUTLOOK AREA IS KEPT UNCHANGED FOR NOW. BY LATE WEEK,
ANY REMAINING HEAVY RAINFALL SHOULD BE ACROSS SOUTHERN TEXAS AHEAD
OF THE FRONT CLEARING OUT THE HIGHEST MOISTURE.
FARTHER WEST, THE CENTRAL ROCKIES AND VICINITY COULD SEE SOME
NOTABLE SNOW AROUND WEDNESDAY-THURSDAY, BUT THE REST OF THE WEST
SHOULD BE DRY ON AVERAGE AS UPPER-LEVEL RIDGING BRIEFLY BUILDS
BACK IN. CHANCES FOR AT LEAST LIGHT PRECIPITATION MAY INCREASE
AGAIN LATE WEEK FOR THE PACIFIC NORTHWEST, BUT WITH UNCERTAINTY IN
TIMING AND AMOUNTS. CURRENT CONSENSUS SHOWING A FAIRLY
WEAK/DIFFUSE SUPPORTING UPPER TROUGH MOVING INTO THE WEST SUGGESTS
THAT MOST PRECIPITATION SHOULD BE CONFINED TO AREAS FROM THE
CENTRAL/NORTHERN WEST COAST INTO THE NORTHERN ROCKIES. THEN
ANOTHER EASTERN PACIFIC TROUGH SHOULD BEGIN TO DIRECT MOISTURE
INTO THE PACIFIC NORTHWEST NEXT WEEKEND, MOST LIKELY OVER NORTHERN
PARTS OF THE REGION.
MUCH OF THE EASTERN TWO-THIRDS OF THE COUNTRY WILL SEE ABOVE
AVERAGE TEMPERATURES AS THE PERIOD BEGINS WEDNESDAY, WITH THE
GREATEST ANOMALIES OF 15-25F FOR HIGHS STRETCHING FROM THE
SOUTHERN PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY AS TEMPERATURES
RISE WELL INTO THE 70S AND 80S. EXPECT A CORRIDOR OF LOWS THAT ARE
20-25F ABOVE NORMAL TO EXTEND ACROSS PARTS OF THE MISSISSIPPI
VALLEY INTO THE OHIO/TENNESSEE VALLEYS ON WEDNESDAY-THURSDAY, WITH
WARMER THAN AVERAGE TEMPERATURES ACROSS THE GULF COAST STATES AS
WELL. DAILY RECORD HIGH MAXIMUM AND MINIMUM TEMPERATURES COULD BE
SET FROM THE SOUTH-CENTRAL U.S. INTO THE TENNESSEE AND OHIO
VALLEYS ESPECIALLY WEDNESDAY. COLD FRONTS TRACKING SOUTH AND EAST
SHOULD GRADUALLY REDUCE THE AREA OF ABOVE NORMAL TEMPERATURES
ACROSS THE CONUS WITH TIME, COOLING TEMPERATURES ACROSS THE
NORTHERN TIER, THEN THE CENTRAL U.S. TO OHIO VALLEY, AND FINALLY
ACROSS THE SOUTHEAST BY FRIDAY-SATURDAY. BEHIND THESE FRONTS, THE
COOLEST ANOMALIES SHOULD BE FOR DAYTIME HIGHS OVER THE SOUTHERN
HALF OF THE HIGH PLAINS LATE IN THE WEEK WITH SOME READINGS UP TO
10-15F BELOW NORMAL. OTHERWISE HIGHS SHOULD DROP TO NEAR OR
SLIGHTLY BELOW NORMAL. AHEAD OF THE SYSTEM REACHING THE NORTHEAST
BY THURSDAY, NEW ENGLAND SHOULD BE ON THE CHILLY SIDE EARLY IN THE
PERIOD AS WELL. MUCH OF THE WEST WILL SEE MODESTLY BELOW NORMAL
HIGHS MID-LATE WEEK BEFORE REBOUNDING TO WITHIN A FEW DEGREES ON
EITHER SIDE OF NORMAL NEXT WEEKEND.
RAUSCH/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 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
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