629
FXUS02 KWBC 051854
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 PM EDT WED OCT 05 2022
VALID 12Z SAT OCT 08 2022 - 12Z WED OCT 12 2022
..OVERVIEW
RATHER AMPLIFIED UPPER LEVEL FLOW IS EXPECTED TO BE IN PLACE THIS
WEEKEND, WITH A GENERAL PATTERN OF TROUGHING ACROSS THE EAST AND
WEST COAST RIDGING (THOUGH WITH A WEAK UPPER LOW/TROUGH ACROSS THE
SOUTHWEST INTO NORTHERN MEXICO MAINTAINING ADDITIONAL SHOWERS AND
STORMS THERE). AT THE SURFACE, A STRONG COLD FRONT WILL BE EXITING
THE ATLANTIC COAST, HERALDING THE ARRIVAL OF A TRULY AUTUMNAL
AIRMASS WITH A BIG CANADIAN SURFACE HIGH SETTLING IN FROM THE
PLAINS TO THE EAST COAST, BEFORE THE NEXT COLD FRONT COMES INTO
THE PLAINS AND GREAT LAKES EARLY NEXT WEEK. AS NEXT WEEK
PROGRESSES, A PATTERN FLIP IS BECOMING INCREASINGLY LIKELY AS
POTENT ENERGY DIGS A TROUGH AND POSSIBLY AN UPPER LOW INTO THE
WEST TUESDAY-WEDNESDAY, BRINGING MUCH COOLER TEMPERATURES AND THE
POSSIBILITY FOR PRECIPITATION INCLUDING HIGHER ELEVATION SNOW
THERE. MEANWHILE, RIDGING COULD FORM DOWNSTREAM INTO THE
EAST-CENTRAL CONUS.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
FOR THE EARLY PART OF THE MEDIUM RANGE PERIOD THIS WEEKEND, MODEL
GUIDANCE IS IN REASONABLY GOOD AGREEMENT WITH A BROAD MID-UPPER
TROUGH IN THE CENTRAL/EASTERN U.S. AND EVEN WITH AN INITIAL
SHORTWAVE NEAR THE LOWER GREAT LAKES SATURDAY MORNING. MODELS ALSO
SHOW GOOD CONSENSUS FOR AN UPPER HIGH CENTERED OVER THE EASTERN
PACIFIC WITH ITS RIDGING INFLUENCE INTO THE WEST COAST, WHILE A
WEAK UPPER LOW OVER NORTHWESTERN MEXICO EXTENDING INTO SOUTHERN
ARIZONA OPENS INTO A TROUGH. THUS THE WPC FRONTS/PRESSURES MODEL
BLEND BEGAN WITH A DETERMINISTIC MULTI-MODEL COMBINATION. MORE
DIFFERENCES START TO ARISE WITH SHORTWAVES IN THE NORTH-CENTRAL
U.S. DURING THE SUNDAY-MONDAY TIMEFRAME, AND THESE MODEL
DIFFERENCES LED TO THE INCLUSION OF THE GEFS AND EC ENSEMBLE MEANS
INTO THE BLEND TO TEMPER THEM.
BY MONDAY, ENERGY IS LIKELY TO DIVE ACROSS WESTERN CANADA AND
DEEPEN TROUGHING OVER THE WEST INTO TUESDAY-WEDNESDAY. THIS
PATTERN HAS BEEN PERSISTENTLY SHOWN BY MULTIPLE RUNS OF THE ECMWF
AND THE PAST COUPLE OF THE CMC RUNS, WHILE GFS RUNS HAVE WAFFLED.
BUT THE 00Z/06Z GFS SHOWED A SIMILAR PATTERN OF TROUGHING, AND
MOST 00Z/06Z GUIDANCE ALSO INDICATED NOT ONLY A TROUGH BUT A
CLOSED LOW FORMING IN THE WEST. THE 00Z CMC WAS AN EXCEPTION BUT
THE 12Z CMC DOES FORM A CLOSED LOW, ALONG WITH OTHER 12Z MODEL
RUNS. THE WPC FORECAST USED A MODEL/MEAN BLEND FOR THE LATTER PART
OF THE MEDIUM RANGE PERIOD, WHICH LED TO A TREND TOWARD THIS UPPER
LOW FEATURE IN THE WPC 500MB CHARTS AND ALSO WITH HIGHER QPF AND
SOME EXTENSION OF QPF WESTWARD IN THE WEST COMPARED TO CONTINUITY,
AS CONFIDENCE GROWS SOMEWHAT IN THIS TYPE OF PATTERN. QPF FROM THE
13Z NBM WAS GENERALLY FOLLOWED, THOUGH WITH AN EXPANSION OF THE
LIGHTER AMOUNTS, AS A KNOWN BIAS OF THE NBM IS TO HAVE NOT ENOUGH
LIGHT PRECIPITATION.
..WEATHER/HAZARDS HIGHLIGHTS
THE COMBINATION OF PERSISTENT MONSOONAL MOISTURE AND AN UPPER LOW
EVOLVING INTO A TROUGH 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. MOISTURE MAY STREAM FARTHER EAST INTO
THE SOUTHERN HALF OF THE PLAINS AND INTERACT WITH A FRONT, LEADING
TO RAIN CHANCES IN THAT AREA AS WELL. THEN THE AMPLIFYING UPPER
TROUGH AND A STRONG COLD FRONT REACHING THE NORTHWEST/NORTHERN
ROCKIES BY NEXT TUESDAY-WEDNESDAY WILL LIKELY PRODUCE
PRECIPITATION ACROSS THOSE AREAS, WITH SNOW BECOMING MORE LIKELY
FOR HIGHER ELEVATIONS OF THE NORTHERN ROCKIES FOR THE TUESDAY AND
WEDNESDAY TIME PERIOD. MOISTURE STREAMING IN AHEAD OF THE TROUGH
AND A FRONTAL SYSTEM COULD HELP PRODUCE RAIN SHOWERS ACROSS MUCH
OF THE CENTRAL U.S. BY THAT TIME AS WELL. ELSEWHERE, LIGHT TO
LOCALLY MODERATE RAINFALL IS FORECAST TO 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. THEN A COOLING TREND WILL COMMENCE BY TUESDAY
AS THE COLD FRONT DROPS SOUTHEASTWARD, PRODUCING HIGH TEMPERATURES
MORE TYPICAL OF MID-LATE NOVEMBER ACROSS THE ROCKIES AND NORTHERN
PLAINS BY NEXT WEDNESDAY AS HIGHS COULD BE UP TO 20 DEGREES BELOW
AVERAGE. FARTHER EAST, AN AREA OF WELL BELOW NORMAL TEMPERATURES
BY AROUND 10-15F IS FORECAST FROM THE MIDWEST TO THE EAST COAST
THIS WEEKEND, WITH HIGHS PERHAPS CLOSER TO 20 DEGREES BELOW NORMAL
IN THE CENTRAL APPALACHIANS. 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 AND
INTERIOR NORTHEAST, WITH THE POTENTIAL FOR THE FIRST FROST/FREEZE
OF THE SEASON FOR MANY AREAS.
TATE/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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