835
FXUS02 KWBC 061853
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
153 PM EST MON NOV 06 2023
VALID 12Z THU NOV 09 2023 - 12Z MON NOV 13 2023
..OVERVIEW
IT GENERALLY REMAINS THE CASE THAT 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
MODELS AND ENSEMBLES CONTINUE TO SHOW A REASONABLY SIMILAR
MID-LARGER SCALE PATTERN EVOLUTION THROUGH MEDIUM RANGE TIME
SCALES, ALBEIT WITH AMPLE TIMING/AMPLITUDE ISSUES WITH SMALL-MID
SCALE
EMBEDDED WEATHER FEATURES AND LOCAL FOCUS. THE WPC MEDIUM RANGE
PRODUCT SUITE WAS PRIMARILY DERIVED FROM A COMPOSITE BLEND OF NOW
BEST CLUSTERED GUIDANCE FROM THE 06 UTC GFS/GEFS AND 00 UTC
ECMWF/ECMWF ENSEMBLE MEAN ALONG WITH THE 13 UTC NATIONAL BLEND OF
MODELS (NBM). THESE PIECES OF GUIDANCE SEEM TO BEST TRANSLATE FROM
UPSTREAM FLOW OVER THE EASTERN PACIFIC AND ALASKA AS WELL AS WPC
CONTINUITY. LATEST 12 UTC GUIDANCE OVERALL CONTINUES SIMILAR
TRENDS.
..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 WAS MAINTAINED IN THE DAY 4/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, WHICH SHOULD CONTINUE TO BE NARROWED WITH TIME AS
MODELS CONVERGE. 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
TO REMAIN FOR THAT REGION FOR THE DAY 5/FRIDAY ERO.
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.
SCHICHTEL/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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