599
FXUS02 KWBC 060714
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
213 AM EST MON NOV 06 2023
VALID 12Z THU NOV 09 2023 - 12Z MON NOV 13 2023
..OVERVIEW
THE UPPER FLOW PATTERN ACROSS THE CONTIGUOUS U.S. DURING THE
LATTER PART OF THIS WEEK INTO EARLY NEXT WEEK LOOKS TO BE
PROGRESSIVE WITH MULTIPLE EMBEDDED SHORTWAVES THAT WILL BE
IMPACTFUL IN SPINNING UP LOW PRESSURE/FRONTAL SYSTEMS. THE FIRST
SYSTEM OF CONCERN IS A POSITIVELY TILTED SHORTWAVE OVER THE FOUR
CORNERS THURSDAY COMBINING WITH CANADIAN FLOW TO PRODUCE TROUGHING
ACROSS THE MIDWEST/GREAT LAKES AND NORTHEAST LATE WEEK. 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. UPSTREAM, 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 MULTIPLE PARTS OF THE FORECAST. WITH THE EASTERN
SYSTEM, THE 12Z UKMET SEEMED OFF INITIALLY WITH THE FOUR CORNERS
SHORTWAVE AND WITH THE CANADIAN ENERGY, AND WAS NOT FAVORED. GFS
RUNS OVER THE PAST DAY OR SO HAVE USUALLY BEEN ON THE FARTHER
NORTH SIDE WITH THE ASSOCIATED SURFACE LOW, INCLUDING THE 18Z GFS,
BUT THE 12Z RUN DID CLUSTER BETTER WITH THE NON-NCEP GUIDANCE.
TOOK A COMPROMISE APPROACH WITH A BLEND OF THE 12Z GFS/ECMWF/CMC
GUIDANCE ALONG WITH THE ENSEMBLE MEANS FOR THIS FEATURE. OVERALL
THIS SYSTEM HAS PERHAPS MORE UNCERTAINTY THAN NORMAL FOR A DAYS
3-5 FORECAST, BUT NOT AS BAD AS UPSTREAM.
THEN MODELS CONTINUE TO SHOW SHORTWAVE TROUGHING COMING INTO THE
WEST AROUND FRIDAY, WITH OVERALL A TREND TOWARD SHALLOWER/WEAKER
ENERGY THAN SOME GUIDANCE FROM A DAY OR TWO AGO. BUT THE TIMING OF
THE SHORTWAVE TRACKING INLAND AROUND SATURDAY HAS VARIED QUITE A
BIT, TO THE POINT OF HAVING SOME MODELS OUT OF PHASE WITH EACH
OTHER AND MAKING IT DIFFICULT TO BLEND GUIDANCE. THE ECMWF HAS
BEEN THE SLOWEST IN MOVING THE SHORTWAVE EAST, BUT WITH SUPPORT
FROM THE ECMWF MEAN. INTERESTINGLY THE ECMWF MACHINE LEARNING
MODELS DID NOT HAVE AS SLOW OF A SHORTWAVE, AND CLUSTERED BETTER
WITH THE GFS/CMC AND THEIR MEANS. SO LEANED MORE TOWARD THE
GFS/GEFS MEAN/CMC HANDLING OF THE SHORTWAVE TIMING, AND IT SEEMED
SIMILAR TO THE PREVIOUS FORECAST. IN TERMS OF THE NEWER 00Z
GUIDANCE, THE GFS HAS SLOWED A BIT COMPARED TO THE PREVIOUS RUNS
(THOUGH NOT TO THE POINT OF THE ECMWF RUNS), AND IS STRONGER WITH
THE ENERGY, EVEN CLOSING OFF A LOW TEMPORARILY ON SATURDAY. THE
12Z AND NOW 00Z ECMWF RUNS, NOW ALONG WITH THE 00Z GFS, DIG THIS
STRONGER ENERGY INTO THE CENTRAL U.S. SUNDAY AND PUSHES
CONSIDERABLE TROUGHING EAST BY MONDAY, A NEW TREND FOR THE GFS.
MEANWHILE FARTHER WEST MOST MODELS AGREE ON A BOUT OF RIDGING OVER
THE WESTERN TO CENTRAL CONUS. THE 12Z AND NEWER 00Z CMC SHOW SOME
EXCEPTION THOUGH, PRESSING A TROUGH INTO THE NORTH-CENTRAL U.S. TO
SUPPRESS IT. THE BELOW AVERAGE CONFIDENCE LED TO A FORECAST
FAVORING PARTICULARLY THE GEFS MEAN THROUGH THE LATTER PART OF THE
PERIOD WITH ONLY A BIT OF THE DETERMINISTIC MODELS (MOSTLY THE 12Z
GFS) REMAINING. EXPECT FORECAST DETAILS TO CHANGE IN FUTURE
ISSUANCES IN THIS UNCERTAIN PATTERN.
..WEATHER/HAZARDS HIGHLIGHTS
AS A NOTABLE SHORTWAVE AND ITS SURFACE LOW REFLECTION TRACK EAST
THROUGH 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. NORTHERN NEW ENGLAND COULD SEE THE BEST
POTENTIAL FOR SNOW ON THURSDAY, BUT LOW CONFIDENCE IN SNOW LEVELS
AND AMOUNTS REMAIN. LIGHT LAKE EFFECT PRECIPITATION WILL BE
POSSIBLE AFTER THIS SYSTEM PASSES. RAIN OF VARYING INTENSITY IS
POSSIBLE FARTHER SOUTHWEST ALONG THE FRONTAL CORRIDOR, LIKELY
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 4/FRIDAY 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, WHICH COULD BE NARROWED WITH TIME AS MODELS
CONVERGE, BUT THAT HAS NOT HAPPENED YET. THE RAINFALL AXIS WILL
SHIFT EAST WITH THE FRONT ON FRIDAY, WITH SHOWERS ACROSS THE
SOUTHEAST INTO THE SOUTHERN/CENTRAL APPALACHIANS AND MID-ATLANTIC.
ANY EXCESSIVE RAINFALL SHOULD BE LIMITED TO COASTAL TEXAS AHEAD OF
THE FRONT CLEARING OUT THE HIGHEST MOISTURE, SO A MARGINAL RISK IS
PLANNED FOR THAT REGION.
FARTHER WEST, THE SOUTH-CENTRAL ROCKIES COULD SEE SNOW CHANCES
LINGERING INTO THURSDAY. THE NORTHWEST LOOKS TO SEE PRECIPITATION
CHANCES PICK UP AGAIN ON THURSDAY-FRIDAY WITH TROUGHING COMING
THROUGH THE REGION. UNCERTAINTY IN TIMING AND AMOUNTS OF THE
PRECIPITATION REMAINS, BUT THE PACIFIC NORTHWEST INTO NORTHERN
CALIFORNIA AND THE NORTHERN ROCKIES COULD SEE MODERATE
PRECIPITATION AMOUNTS, WITH LOWER ELEVATION RAIN AND HIGHER
ELEVATION SNOW. THEN ANOTHER EASTERN PACIFIC TROUGH SHOULD BEGIN
TO DIRECT MOISTURE INTO THE PACIFIC NORTHWEST OVER THE WEEKEND,
MOST LIKELY OVER NORTHERN PARTS OF THE REGION.
SOUTH-CENTRAL TO EASTERN PORTIONS OF THE COUNTRY WILL REMAIN
WARMER THAN AVERAGE AHEAD OF THE FRONTAL BOUNDARY ON THURSDAY,
WITH A CORRIDOR OF LOWS THAT ARE 20-25F ABOVE NORMAL EXTENDING
FROM PARTS OF THE MISSISSIPPI VALLEY INTO THE TENNESSEE AND OHIO
VALLEYS THURSDAY MORNING THAT COULD SET DAILY RECORDS. THE COLD
FRONT WILL BE ON ITS WAY THROUGH THOSE REGIONS THOUGH, SO HIGHS
MAY ONLY WARM TO 5-10F ABOVE AVERAGE THERE ON THURSDAY, WITH
GREATER WARM ANOMALIES FOR HIGHS FARTHER SOUTH ACROSS THE
SOUTHEAST TO MID-ATLANTIC. WARM LOWS FRIDAY MORNING SHOULD BE
LOCATED OVER SIMILAR REGIONS, BUT HIGHS SHOULD COOL TO NEAR OR
BELOW NORMAL IN MUCH OF THE SOUTHEASTERN CONUS. BY THE WEEKEND,
THE MAIN AREA REMAINING ABOVE AVERAGE WILL BE THE FLORIDA
PENINSULA, WITH HIGHS WELL INTO THE 80S ACTUALLY CLOSE TO DAILY
RECORD HIGHS. ELSEWHERE TEMPERATURES SHOULD BE COOLER AND NEAR
NORMAL FOR THE WEEKEND. A TREND TOWARD UPPER-LEVEL RIDGING BY
EARLY NEXT WEEK ACROSS THE CENTRAL U.S. WOULD LEAD TO TEMPERATURES
WARMING TO AROUND 10F ABOVE AVERAGE ACROSS THE NORTHERN HALF OF
THE PLAINS INTO THE UPPER MIDWEST BY NEXT MONDAY.
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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