987
FXUS02 KWBC 191907
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT WED OCT 19 2022
VALID 12Z SAT OCT 22 2022 - 12Z WED OCT 26 2022
..OVERVIEW
AN ENERGETIC UPPER-LEVEL TROUGH ARRIVING AND AMPLIFYING OVER THE
PACIFIC NORTHWEST AT THE START OF THE MEDIUM-RANGE PERIOD WILL
LIKELY BECOME A MAJOR WEATHER PLAYER AS THE TROUGH PROGRESSES
FURTHER DOWNSTREAM INTO THE PLAINS DURING THE WEEKEND. MEANWHILE,
A SOUTHERN STREAM UPPER LOW CONTINUES TO INTRODUCE UNCERTAINTY
INTO THE FORECAST DUE TO CONTINUED POOR MODEL AGREEMENT ON THE
TIMING OF INTERACTION/PHASING OF THE SOUTHERN STREAM LOW WITH THE
NORTHERN STREAM TROUGH. ANOTHER AREA OF UNCERTAINTY IS ALONG THE
EAST COAST WHERE MODEL AGREEMENT REMAINS POOR REGARDING THE DEGREE
OF INTERACTION BETWEEN A SMALLER SCALE UPPER LOW AND A LINGERING
SLOW-MOVING FRONT JUST OFFSHORE.
..MODEL AND PREDICTABILITY ASSESSMENT
WHILE MODEL GUIDANCE STARTS OUT WITH DECENT AGREEMENT ON THE
AMPLIFYING TROUGHING IN THE WEST THIS WEEKEND, PREDICTABILITY AND
CONFIDENCE QUICKLY DECREASE EARLY NEXT WEEK AS MODELS CONTINUE
WITH THE EXPECTED STRUGGLE OF RESOLVING ITS INTERACTION WITH THE
SOUTHERN STREAM UPPER LOW MOVING ONSHORE ACROSS BAJA CALIFORNIA.
IN GENERAL, MODELS HAVE TRENDED TOWARD A FASTER DOWNSTREAM
PROGRESSION OF THE FRONT ACROSS THE PLAINS EARLY NEXT WEEK AND
INTO THE EASTERN U.S. BY MIDWEEK. THE 00Z CANADIAN MODEL WAS AN
OUTLIER WITH AN MUCH EARLIER PHASING OF THE SOUTHERN STREAM LOW
THIS WEEKEND THAN THE REST OF THE GUIDANCE. AS FOR THE EAST
COAST, THERE HAS BEEN A GRADUAL TENDENCY FOR THE RAIN TO EDGE
CLOSER TO LAND. THE ECMWF HAS OCCASIONALLY BEEN THE MOST
AGGRESSIVE IN THIS REGARD. THE 12Z GFS HAS INDICATED THIS
TENDENCY AS WELL. IT APPEARS THE THREAT OF ENHANCED RAINFALL WILL
BE MORE LIKELY ACROSS COASTAL NEW ENGLAND.
THE WPC FORECAST WAS BASED ON A BLEND OF THE 00Z ECMWF/EC MEAN
WITH THE 06Z GFS/GEFS, LEANING TOWARD THE EC/EC MEAN BLEND BY DAYS
6 AND 7. THIS RESULTS IN A FASTER EASTWARD PROGRESSION OF THE
FRONT FROM THE PLAINS TOWARD THE EASTERN U.S. EARLY TO MIDDLE OF
NEXT WEEK THAN IN PREVIOUS WPC FORECASTS.
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
PRECIPITATION IS LIKELY ACROSS THE MUCH OF THE WEST BY SATURDAY AS
THE UPPER TROUGH AMPLIFIES AND THE FIRST SURFACE COLD FRONT MOVES
THROUGH, FOR ONE OF THE FIRST MAJOR COOL SEASON-TYPE PRECIPITATION
EVENTS SINCE MUCH EARLIER THIS YEAR. PRECIPITATION WILL BE
ENHANCED ACROSS FAVORED WINDWARD TERRAIN OF THE CASCADES, ROCKIES,
AND WASATCH OVER THE WEEKEND, WITH HIGHER ELEVATION SNOW AND LOWER
ELEVATION RAIN. CONFIDENCE IN A MEANINGFUL PRECIPITATION EVENT
REMAINS FAIRLY GOOD, BUT EXACT AMOUNTS OF RAIN/SNOW AND TIMING
WILL STILL NEED TO BE REFINED WITH TIME. ANOTHER COUPLE OF ROUNDS
OF PRECIPITATION COULD CONTINUE/REFORM EARLY NEXT WEEK IN THE
NORTHWEST BUT WITH EVEN MORE UNCERTAINTY. PRECIPITATION MAY ALSO
BE POSSIBLE ACROSS THE SOUTHWEST FOR THE WEEKEND BUT WILL BE
DEPENDENT ON THE TIMING AND TRACK OF THE SOUTHERN STREAM LOW AND
ITS EVENTUAL POSSIBLE PHASING. BY EARLY NEXT WEEK, PRECIPITATION
CHANCES SHOULD GENERALLY INCREASE ACROSS THE PLAINS AND INTO THE
MISSISSIPPI VALLEY AHEAD OF THE UPPER TROUGH AND A DEVELOPING LOW
PRESSURE SYSTEM. AREAS OF ENHANCED TO POSSIBLY HEAVY RAINFALL ARE
LIKELY, WHILE THERE MAY BE SOME SNOW ON THE BACKSIDE OF THE
SURFACE LOW INTO THE NORTHERN HIGH PLAINS, BUT THE SPECIFICS OF
BOTH ARE NOT YET CLEAR AT THIS TIME. MEANWHILE, SOME RAIN MAY BE
POSSIBLE ALONG OR NEAR THE EAST COAST THIS WEEKEND INTO MONDAY
ASSOCIATED WITH A FRONTAL BOUNDARY AND POSSIBLE LOW PRESSURE
SYSTEM, BUT WITH LOW CONFIDENCE ON HOW MUCH RAIN COULD FALL
ONSHORE VERSUS REMAINING OFFSHORE.
TEMPERATURES ARE LIKELY TO BE WARMER THAN AVERAGE ACROSS THE
CENTRAL U.S. FOR THE WEEKEND AHEAD OF THE DEVELOPING WESTERN UPPER
TROUGH. HIGHS AND LOWS OF 10-20F ABOVE NORMAL, WITH SOME SPOTS
HIGHER, WILL BE WIDESPREAD ACROSS THE PLAINS TO UPPER MIDWEST.
MEANWHILE, AN AREA OF BELOW NORMAL TEMPERATURES WILL EXPAND FROM
THE WEST COAST STATES INTO THE GREAT BASIN AND ROCKIES THIS
WEEKEND, WITH LOWS AROUND 5-15F BELOW AVERAGE AND HIGHS 10-20F
BELOW AVERAGE. TEMPERATURES SHOULD COOL TO NEAR NORMAL AND EVEN
BELOW NORMAL FOR THE NORTH-CENTRAL U.S. NEXT WEEK AS THE UPPER
TROUGH AND COLD FRONT(S) MOVE THROUGH. THIS WILL PUSH WARMER THAN
AVERAGE TEMPERATURES INTO THE NORTHEASTERN U.S. BY
MONDAY-WEDNESDAY.
KONG/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, 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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