643
FXUS02 KWBC 080700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST WED NOV 08 2023
VALID 12Z SAT NOV 11 2023 - 12Z WED NOV 15 2023
..OVERVIEW
OVER THE WEEKEND, A SHORTWAVE OR TWO WILL PUSH THROUGH THE
NORTHERN TIER OF THE COUNTRY, DEVELOPING INTO TROUGHING OVER THE
EASTERN SEABOARD EARLY NEXT WEEK AND LEADING TO COOLER THAN
AVERAGE TEMPERATURES. FARTHER SOUTH, MOISTURE SHOULD OVERRUN A
SLOW-MOVING FRONT OVER THE GULF OF MEXICO AND SPREAD RAIN ACROSS
PARTS OF THE SOUTHERN AND EASTERN U.S. SOUTHERN TEXAS MAY SEE THE
BEST CHANCE FOR HEAVY RAIN ESPECIALLY INTO NEXT WEEK WHEN
UPPER-LEVEL ENERGY COMES THROUGH, BUT THERE IS STILL CONSIDERABLE
UNCERTAINTY WITH HOW MUCH RAIN FALLS ONSHORE VERSUS OFFSHORE AND
HOW MUCH INSTABILITY WILL BE IN PLACE THAT WOULD INCREASE RAIN
RATES. MEANWHILE, ROUNDS OF PRECIPITATION ARE POSSIBLE ACROSS THE
PACIFIC NORTHWEST FOR THE WEEKEND INTO EARLY NEXT WEEK, BUT
PRECIPITATION LOOKS TO INCREASE CONSIDERABLY FOR THE WEST COAST
(MOST LIKELY MAXIMIZED OVER CALIFORNIA) BY TUESDAY-WEDNESDAY AS
DEEP EASTERN PACIFIC UPPER TROUGHING LIKELY DIRECTS AN ATMOSPHERIC
RIVER INTO THE REGION. DOWNSTREAM, UPPER RIDGING IN THE
NORTH-CENTRAL U.S. SHOULD LEAD TO ABOVE AVERAGE TEMPERATURES FOR
THE NORTHERN/CENTRAL PLAINS INTO THE MIDWEST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE DETAILS OF SHORTWAVES TRACKING ACROSS THE NORTHERN TIER REMAIN
UNCERTAIN THIS WEEKEND EARLY IN THE MEDIUM RANGE PERIOD. SPLIT
FLOW OVER THE GREAT LAKES AROUND SUNDAY COMPLICATES MATTERS TOO,
WITH VARIATIONS IN MODELS WITH WHERE THE TROUGHING FARTHER SOUTH
IN THE MIDWEST SPLITS WITH RIDGING FARTHER NORTH INTO SOUTHERN
CANADA. WITH THE 12/18Z SUITE OF GUIDANCE THERE DID NOT SEEM TO BE
PARTICULAR OUTLIERS THROUGH THE WEEKEND, SO UTILIZED A MULTI-MODEL
DETERMINISTIC BLEND FAVORING THE 18Z GFS AND 12Z ECMWF. THOUGH
INTO THE WORKWEEK AS ENERGY COMBINES TO FORM TROUGHING OVER THE
EAST, THE ECMWF SEEMS TO STRAY FASTER THAN CONSENSUS WITH THE
EASTWARD MOVEMENT OF THE TROUGH INTO THE ATLANTIC. THE NEWER 00Z
ECMWF SEEMS SLOWER BUT ALSO FLATTER WITH THE TROUGH.
FORTUNATELY THE UPPER PATTERN BECOMES MORE DOMINATED BY
SYNOPTIC-SCALE LONGWAVE TROUGHS AND RIDGES INTO NEXT WEEK. FLOW ON
THIS SCALE IS USUALLY BETTER HANDLED BY THE MODEL GUIDANCE, THOUGH
SOME MODEL DIFFERENCES REMAIN PARTICULARLY IN TERMS OF THE TIMING
OF THE FEATURES. OVERALL MODELS ARE AGREEABLE THAT EASTERN PACIFIC
TROUGHING WILL DEEPEN AND EDGE TOWARD THE WEST COAST, WHILE
RIDGING AMPLIFIES FARTHER EAST OVER THE CENTRAL U.S. AND TROUGHING
OVER THE EAST TRACKS INTO THE ATLANTIC BY MIDWEEK. THE PACIFIC
TROUGH HAS SHOWN SOME NOTABLE DIFFERENCES IN ITS TIMING OVER THE
PAST COUPLE OF DAYS. THE ECMWF SUITE HAS BEEN FASTER IN BRINGING
THE TROUGH AND LIKELY EMBEDDED UPPER LOW AND THUS THE QPF INLAND
COMPARED TO THE OTHER GUIDANCE. THE NEWER 00Z ECMWF RUN HAS SLOWED
DOWN THOUGH AND LOOKS MORE CONSISTENT WITH CONSENSUS. ANOTHER
CONSIDERATION IS ENERGY ATOP NORTHWESTERN MEXICO EARLY IN THE WEEK
THAT SHOULD TRACK NORTHEAST ACROSS THE SOUTH-CENTRAL U.S. AROUND
MONDAY-WEDNESDAY. MODELS GENERALLY AGREE ON THIS TRACK BUT EVEN
MINOR DIFFERENCES CAN CAUSE DISCREPANCIES WITH THE SENSIBLE
WEATHER SUCH AS THE QPF--THE 12Z ECMWF WAS QUITE HIGH WITH ITS QPF
AND FARTHER INLAND COMPARED TO OTHER GUIDANCE. THE NEWER 00Z ECMWF
SEEMS STILL FARTHER INLAND AND HEAVY COMPARED TO OTHER GUIDANCE,
BUT AT LEAST NOT TO THE SAME EXTREME AS THE PREVIOUS RUN.
THE WPC FORECAST TRANSITIONED FROM A MULTI-MODEL DETERMINISTIC
BLEND OF THE 18Z GFS AND 12Z ECMWF/CMC/UKMET TO INCORPORATE THE
GEFS AND EC ENSEMBLE MEANS IN THE BLEND, WITH HALF MODELS/HALF
MEANS COMPOSING THE FORECAST BLEND BY DAYS 6-7. THIS MINIMIZED
INDIVIDUAL MODEL DIFFERENCES WHILE CAPTURING THE OVERALL PATTERN.
..WEATHER/HAZARDS HIGHLIGHTS
MOISTURE OVERRUNNING THE COLD FRONT THAT IS FORECAST TO STALL OVER
THE NORTHWESTERN GULF (BUT TRACK A BIT MORE PROGRESSIVELY THROUGH
FLORIDA) WILL LEAD TO SOME RAIN ACROSS THE SOUTH-CENTRAL TO
SOUTHEASTERN QUADRANT OF THE U.S. FOR THE WEEKEND 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. NOT MUCH INSTABILITY IS
LIKELY TO BE IN PLACE SINCE THIS WILL BE AFTER THE FRONTAL
PASSAGE, SO RAIN RATES SHOULD NOT BE TOO HIGH. THERE IS ALSO
CONSIDERABLE UNCERTAINTY WITH HOW MUCH RAIN SPREADS INLAND, WITH
RAIN TOTALS MAXIMIZED OVER THE GULF. THUS THROUGH THE WEEKEND,
THERE ARE NO FLASH FLOODING AREAS DELINEATED IN THE EXCESSIVE
RAINFALL OUTLOOK. INTO MONDAY AND BEYOND THOUGH, THERE MAY BE MORE
SUPPORT FOR CONVECTION FROM TEXAS INTO THE LOWER MISSISSIPPI
VALLEY AS MID-UPPER LEVEL ENERGY APPROACHES, SO THIS WILL CONTINUE
TO BE MONITORED.
ROUNDS OF FRONTAL SYSTEMS AND SHORTWAVES PUSHING THROUGH THE
NORTHWEST WILL MAINTAIN PRECIPITATION CHANCES ACROSS THE PACIFIC
NORTHWEST AND THE NORTHERN ROCKIES OVER THE WEEKEND. 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. STARTING MONDAY AND ESPECIALLY BY
TUESDAY-WEDNESDAY, UPPER TROUGHING WILL DEEPEN OVER THE EASTERN
PACIFIC AND DIRECT MOISTURE PLUMES/ATMOSPHERIC RIVERS INTO THE
WEST, ESPECIALLY CALIFORNIA. EXPECT HEAVY LOWER ELEVATION RAIN AND
HIGHER ELEVATION SNOW.
ON SATURDAY, MOST OF THE LOWER 48 WILL BE UNDER A POST-FRONTAL
COOL HIGH PRESSURE SYSTEM, WITH TEMPERATURES NEAR TO BELOW
AVERAGE. THE EXCEPTION WILL BE THE FLORIDA PENINSULA, WITH HIGHS
WELL INTO THE 80S ACTUALLY CLOSE TO DAILY RECORD HIGHS.
TEMPERATURES OVER FLORIDA SHOULD GRADUALLY MODERATE TO NEAR NORMAL
EARLY NEXT WEEK AS THE COLD FRONT PRESSES THROUGH. AS UPPER
RIDGING BUILDS ACROSS THE NORTH-CENTRAL U.S. EARLY NEXT WEEK,
ABOVE NORMAL TEMPERATURES BY AROUND 10-20F WILL OVERSPREAD THE
CENTRAL AND NORTHERN PLAINS INTO THE MIDWEST, WITH SOME ABOVE
AVERAGE POCKETS BACK INTO THE GREAT BASIN AS WELL. 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
TEMPERATURES 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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