698
FXUS02 KWBC 071901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST TUE NOV 07 2023
VALID 12Z FRI NOV 10 2023 - 12Z TUE NOV 14 2023
..OVERVIEW
THE UPPER FLOW PATTERN ACROSS THE CONTIGUOUS U.S. LATE WEEK INTO
THE WEEKEND 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 NORTH-CENTRAL U.S. FRIDAY
COMBINING WITH CANADIAN FLOW TO PRODUCE TROUGHING ACROSS PARTS OF
THE CENTRAL AND EASTERN U.S. LATE WEEK. EASTWARD PROGRESSION OF
THE UPPER TROUGH AND AN ASSOCIATED WAVY FRONT WILL GRADUALLY
SUPPRESS AN AREA OF ABOVE AVERAGE TEMPERATURES ACROSS THE
SOUTHEAST LATE WEEK, WHILE SPREADING RAIN ACROSS THE SOUTHERN AND
EASTERN U.S. THAT COULD LINGER INTO EARLY NEXT WEEK. UPSTREAM, A
QUICKLY MOVING SHORTWAVE AND FRONTAL SYSTEM OR TWO COMING THROUGH
THE NORTHWEST SHOULD INCREASE RAIN/SNOW CHANCES THERE, FOLLOWED BY
A LARGER SCALE EASTERN PACIFIC UPPER TROUGH THAT MAY GENERATE
ADDITIONAL PRECIPITATION OVER THE PACIFIC NORTHWEST DURING THE
WEEKEND AND BEYOND. THIS EASTERN PACIFIC TROUGH WILL PROMOTE UPPER
RIDGING FARTHER EAST INTO THE NORTH-CENTRAL U.S. WITH WARMER
TEMPERATURES, AND OVERALL A MORE LONGWAVE-DOMINATED PATTERN INTO
NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
DESPITE SOME RELATIVELY MINOR DETAIL DIFFERENCES, THERE REMAINS
GOOD ENOUGH AGREEMENT THE FIRST HALF OF THE PERIOD FOR A
MULTI-MODEL BLEND OF THE LATEST DETERMINISTIC GUIDANCE. BY SUNDAY
AND BEYOND, BIGGER ISSUES BEGIN TO ARISE REGARDING A SHORTWAVE
TRAVERSING THE NORTHERN HALF OF THE COUNTRY REACHING THE GREAT
LAKES AROUND SUNDAY. THE ECMWF BY THIS POINT BECOMES FASTER AND
MORE AMPLIFIED AS IT TRIES TO COMBINE ENERGIES WITH A SEPARATE
SHORTWAVE MOVING INTO THE GREAT LAKES ON SUNDAY FROM CENTRAL
CANADA AND ALSO SPINS UP A DEEP SURFACE LOW OFF THE EAST COAST ON
MONDAY. THE BETTER CONSENSUS SUGGESTS MORE SEPARATION OF FEATURES
AND WEAKER SYSTEMS, AND BY DAY 7, THE ECMWF BECOMES COMPLETELY OUT
OF PHASE ACROSS THE EAST COMPARED TO THE GFS/CMC. THIS HAS
IMPLICATIONS FOR QPF ACROSS THE EAST/SOUTHEAST THIS WEEKEND/EARLY
NEXT WEEK. THE ENSEMBLE MEANS SHOW BETTER AGREEMENT AND SUGGESTS A
TROUGH POSITION IN BETWEEN THE GFS/CMC AND THE ECMWF. TIMING
ISSUES BEGIN TO ARISE BY MONDAY AND ESPECIALLY INTO TUESDAY WITH
AMPLIFIED TROUGHING TOWARDS THE WEST COAST WITH THE ECMWF QUITE A
BIT FASTER BRINGING THIS ENERGY (AND THE RESULTING QPF) INLAND.
THE ENSEMBLE MEANS GENERALLY FOLLOW SUIT WITH THEIR DETERMINISTIC
COUNTERPARTS.
THE WPC FORECAST FOR TODAY USED A GENERAL MODEL BLEND FOR DAYS
3-5, LEANING MORE HEAVILY ON THE ENSEMBLE MEANS BY DAY 6 AND
7/MONDAY-TUESDAY. MAINTAINED A SLIGHT PREFERENCE TOWARDS THE
SLOWER GFS/GEFS WHICH MAINTAINED BETTER CONTINUITY WITH THE
PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
MOISTURE OVERRUNNING THE COLD FRONT THAT IS LIKELY TO PUSH THROUGH
THE SOUTHEAST AND THEN STALL OVER THE NORTHERN GULF WILL LEAD TO
SOME RAIN ACROSS THE SOUTH-CENTRAL TO SOUTHEASTERN QUADRANT OF THE
U.S. FOR LATE WEEK INTO EARLY NEXT WEEK. THE HIGHEST RAINFALL
TOTALS ARE LIKELY TO BE OVER SOUTHERN TEXAS NEAR A MEANDERING
SURFACE LOW ALONG THE FRONT, WITH EASTERN PACIFIC AND GULF
MOISTURE COMBINING. ON FRIDAY, SOME INSTABILITY COULD BE IN PLACE
ESPECIALLY EARLY IN THE DAY BEFORE THE FRONT PUSHES THROUGH. THIS
COULD LEAD TO LOCALLY HEAVY RAINFALL RATES, BUT ARE LIKELY TO STAY
BELOW ANY FLASH FLOODING THRESHOLDS, SO MAINTAINED NO RISK AREA ON
THE DAY 4/FRIDAY EXCESSIVE RAINFALL OUTLOOK. BY SATURDAY, SINCE
THE FRONT IS LIKELY TO HAVE PASSED, LACK OF INSTABILITY SHOULD
MEAN RAIN RATES WILL NOT BE TOO HIGH, SO NO RISK AREA IS PLANNED
FOR THE DAY 5/SATURDAY ERO EITHER. INTO NEXT WEEK THOUGH, THERE
MAY BE MORE SUPPORT FOR CONVECTION AS MID-UPPER LEVEL ENERGY
APPROACHES, SO THIS WILL CONTINUE TO BE MONITORED. FARTHER NORTH,
LAKE EFFECT PRECIPITATION IS LIKELY WITH TROUGHING AND WESTERLY
FLOW OVER THE GREAT LAKES, LIKELY MAXIMIZED FRIDAY. ADDITIONAL
UPPER-LEVEL ENERGY COULD SPREAD LIGHT PRECIPITATION TO THE
NORTHEAST EARLY NEXT WEEK. ROUNDS OF FRONTAL SYSTEMS AND
SHORTWAVES PUSHING THROUGH THE NORTHWEST WILL MAINTAIN
PRECIPITATION CHANCES ACROSS THE PACIFIC NORTHWEST AND THE
NORTHERN ROCKIES. MODERATE TO HEAVY AMOUNTS ARE LIKELY TO BE
DIRECTED INTO THE NORTHERN PARTS OF THE OLYMPICS AND CASCADES,
WITH LOWER ELEVATION RAIN AND HIGHER ELEVATION SNOW.
SOUTHEASTERN PORTIONS OF THE COUNTRY WILL REMAIN WARMER THAN
AVERAGE AHEAD OF THE FRONTAL BOUNDARY ON FRIDAY, WITH A CORRIDOR
OF LOWS THAT ARE 10-20F ABOVE NORMAL EXTENDING FROM THE LOWER
MISSISSIPPI VALLEY INTO THE SOUTHEAST TO THE MID-ATLANTIC FRIDAY
MORNING BEFORE THE COLD FRONT PASSES AND LIMITS ABOVE NORMAL HIGHS
TO THE SOUTHEAST/FLORIDA. THE FLORIDA PENINSULA SHOULD BE THE MAIN
AREA ABOVE AVERAGE BY SATURDAY, WITH HIGHS WELL INTO THE 80S
ACTUALLY CLOSE TO DAILY RECORD HIGHS. ELSEWHERE, TEMPERATURES
SHOULD BE NEAR AVERAGE TO COOLER THAN AVERAGE THROUGH LATE WEEK IN
THE POST-FRONTAL COOL HIGH PRESSURE. BUT AS UPPER RIDGING BUILDS
ACROSS THE NORTH-CENTRAL U.S. EARLY NEXT WEEK, ABOVE NORMAL
TEMPERATURES BY AROUND 10-15F WILL OVERSPREAD THE CENTRAL AND
NORTHERN PLAINS INTO THE MIDWEST. MEANWHILE BELOW NORMAL HIGHS
SHOULD LINGER IN THE SOUTH-CENTRAL U.S. WITH LOWER HEIGHTS
OVERHEAD AND CLOUDS AND RAIN POSSIBLE, AND INTERESTINGLY LEAD TO
SIMILAR HIGHS FROM TEXAS ALL THE WAY NORTH TO SOUTH DAKOTA OR SO
(IN THE UPPER 50S AND 60S). NEAR TO COOLER THAN NORMAL OVER THE
EASTERN SEABOARD THIS WEEKEND SHOULD GRADUALLY MODERATE THROUGH
THE EARLY PART OF NEXT WEEK.
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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