592
FXUS02 KWBC 050627
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 AM EDT WED OCT 5 2022
VALID 12Z SAT OCT 8 2022 - 12Z WED OCT 12 2022
..SYNOPTIC OVERVIEW
A RATHER AMPLIFIED UPPER LEVEL FLOW PATTERN IS EXPECTED TO BE IN
PLACE FOR THE UPCOMING WEEKEND AND EXTENDING INTO THE EARLY TO
MIDDLE PORTION OF NEXT WEEK. FOR THE EASTERN U.S., A STRONG COLD
FRONT WILL BE EXITING THE COAST AND HERALDING THE ARRIVAL OF A
TRULY AUTUMNAL AIRMASS WITH A BIG CANADIAN SURFACE HIGH SETTLING
IN FROM THE PLAINS TO THE EAST COAST, AND THIS HIGH WILL GRADUALLY
MOVE OFFSHORE EARLY NEXT WEEK AHEAD OF THE NEXT COLD FRONT ACROSS
THE PLAINS AND GREAT LAKES BY THAT TIME. FOR THE WESTERN U.S., A
PERSISTENT WEAK UPPER LOW/TROUGH AXIS WILL MAINTAIN ADDITIONAL
SHOWERS AND STORMS FROM ARIZONA AND ESPECIALLY NEW MEXICO. BY
TUESDAY, A MORE IMPRESSIVE UPPER TROUGH BEGINS BUILDING ACROSS THE
NORTH-CENTRAL U.S. WHICH WILL LIKELY BRING MUCH COOLER CONDITIONS
FOR MUCH OF THE WESTERN U.S. BY THE MIDDLE OF NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
OVERALL, THE 00Z DETERMINISTIC GUIDANCE IS IN GOOD OVERALL
AGREEMENT ON MOST FEATURES FOR SATURDAY, WITH THE MAIN DIFFERENCE
AT THIS TIME BEING A MORE PROGRESSIVE SOLUTION WITH THE GFS ACROSS
THE MID-ATLANTIC WITH THE TROUGH EXITING THE COAST. THE MODELS
ALSO AGREE WELL ON THE UPPER LOW THAT EVOLVES INTO A TROUGH NEAR
THE DESERT SOUTHWEST THROUGH THE WEEKEND. LOOKING AHEAD, SPREAD
AND RUN-TO-RUN VARIABILITY HAVE IMPROVED WITH THE 00Z MODEL CYCLE
FOR THE DEEP TROUGH AMPLIFYING INTO CANADA AND THE NORTHWESTERN
U.S. EARLY NEXT WEEK. RECENT ECMWF RUNS HAVE BEEN MORE CONSISTENT
IN INDICATING MORE TROUGHING OVER THE NORTHWEST AND NORTHERN
ROCKIES, AND THIS ALSO HOLDS TRUE FOR THE PAST TWO RUNS OF THE
CMC. THE GFS HAS VARIED CONSIDERABLY OVER THE EVOLUTION OF THIS
TROUGH, HOWEVER THE MOST RECENT 00Z RUN FALLS MORE IN LINE WITH
THE MODEL CONSENSUS AND THE ENSEMBLE MEANS.
A MULTI-DETERMINISTIC MODEL BLEND SUFFICES EARLY IN THE PERIOD,
FOLLOWED BY INCREASING THE WEIGHTING OF THE ENSEMBLE MEANS FOR
EARLY NEXT WEEK AND REMOVING THE 18Z GFS FROM THE FRONTS/PRESSURES
FORECAST BY WEDNESDAY. FOR THE QPF, THE NBM COMBINED WITH SOME OF
THE OPERATIONAL GFS/ECMWF WAS USED AS A BASELINE THROUGH ABOUT
MONDAY, AND THEN MAINLY WENT WITH NBM FOR TUESDAY/TUESDAY NIGHT.
..WEATHER/HAZARDS HIGHLIGHTS
THE COMBINATION OF PERSISTENT MONSOONAL MOISTURE AND AN UPPER LOW
OVER NORTHWEST MEXICO WILL CONTINUE TO FUEL DIURNAL SHOWERS AND
THUNDERSTORMS OVER PARTS OF THE DESERT SOUTHWEST/SOUTHERN ROCKIES
THROUGH THE WEEKEND, WITH THE GREATEST RAINFALL TOTALS EXPECTED
FOR CENTRAL AND SOUTHERN NEW MEXICO BASED ON LATEST MODEL
GUIDANCE. THE UPPER LOW SHOULD EVOLVE INTO AN OPEN TROUGH BY
MONDAY, BUT MAY BE REPLACED BY ADDITIONAL WEAK ENERGY BUILDING IN
FROM THE NORTHWEST. THIS EVOLUTION MAY HELP TO SPREAD SOME OF THE
MOISTURE EASTWARD INTO THE PLAINS WHERE IT COULD INTERACT WITH A
FRONT. AN AMPLIFYING UPPER TROUGH AND A STRONG COLD FRONT
REACHING THE NORTHWEST/NORTHERN ROCKIES BY NEXT TUESDAY WILL
LIKELY PRODUCE SHOWERS AND PERHAPS EVEN HIGH ELEVATION SNOW FOR
PORTIONS OF THE NORTHERN ROCKIES FOR THE TUESDAY AND WEDNESDAY
TIME PERIOD. ELSEWHERE, LIGHT TO LOCALLY MODERATE RAINFALL WILL
LIKELY SPREAD NORTHWARD OVER THE FLORIDA PENINSULA AS EASTERLY LOW
LEVEL FLOW STRENGTHENS BEHIND A FRONT.
MUCH OF THE WEST SHOULD HAVE ABOVE NORMAL TEMPERATURES AT LEAST
THROUGH MONDAY, WITH HIGHS 10-15F OR SO ABOVE NORMAL MOST LIKELY
OVER THE NORTHWEST, WITH A NOTICEABLE COOLING TREND COMMENCING BY
TUESDAY AS THE COLD FRONT DROPS SOUTHEASTWARD, AND THEN
TEMPERATURES MORE TYPICAL OF MID-LATE NOVEMBER ARE EXPECTED ACROSS
THE ROCKIES AND NORTHERN PLAINS BY NEXT WEDNESDAY WITH HIGHS UP TO
20 DEGREES BELOW AVERAGE. FARTHER EAST, AN AREA OF WELL BELOW
NORMAL TEMPERATURES IS FORECAST FROM THE MIDWEST TO THE EAST COAST
THIS WEEKEND, AND SOME AREAS MAY HAVE HIGHS 15-20F BELOW NORMAL ON
SATURDAY. MORNING LOWS WILL ALSO BE RATHER CHILLY WITH READINGS
INTO THE 30S FOR MANY LOCATIONS FROM THE NORTHERN HALF OF THE
PLAINS INTO THE CENTRAL APPALACHIANS, WITH THE POTENTIAL FOR THE
FIRST FROST/FREEZE OF THE SEASON FOR MANY AREAS.
HAMRICK
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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