718
FXUS02 KWBC 192031
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
431 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 MOVING INTO 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 A MUCH EARLIER PHASING OF THE SOUTHERN
STREAM LOW THIS WEEKEND THAN THE REST OF THE GUIDANCE. MEANWHILE,
CONFIDENCE IS INCREASING FOR A SIGNIFICANT LOW PRESSURE SYSTEM TO
INTENSIFY AND TRACK NORTHEASTWARD ACROSS THE CENTRAL AND NORTHERN
PLAINS SUNDAY TO MONDAY. 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 MUCH OF THE WEST BY SATURDAY WITH
THE ARRIVAL OF THE AMPLIFYING UPPER TROUGH, HURLING IN THE FIRST
MAJOR COOL SEASON-TYPE PRECIPITATION EVENT FOR THE REGION.
PRECIPITATION IN THE FORM OF HIGHER ELEVATION SNOW AND LOWER
ELEVATION RAIN WILL BE ENHANCED ACROSS FAVORED WINDWARD TERRAIN OF
THE CASCADES, ROCKIES, WITH THE HEAVIEST AMOUNTS LIKELY ALONG THE
WASATCH OVER THE WEEKEND. 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 TO MIDDLE OF NEXT WEEK IN THE NORTHWEST AS A COUPLE
ADDITIONAL PACIFIC SYSTEMS ARE FORECAST TO ARRIVE.
BY EARLY NEXT WEEK, AN INTENSIFYING LOW PRESSURE SYSTEM FORECAST
TO TRACK ACROSS THE NORTHERN TO CENTRAL PLAINS SUNDAY TO MONDAY
WILL INCREASE THE THREAT OF HIGH WINDS ACROSS THESE AREAS, ALONG
WITH A THREAT OF RAIN CHANGING TO A PERIOD OF ENHANCED WINTRY
PRECIPITATION ON THE BACK SIDE OF THE LOW NEAR THE CANADIAN
BORDER. FARTHER SOUTH, RAIN CHANCES SHOULD GENERALLY INCREASE
ACROSS THE PLAINS AND INTO THE MISSISSIPPI VALLEY AHEAD OF THE
UPPER TROUGH AND WHAT APPEARS TO BE A POTENT COLD FRONT. AREAS OF
ENHANCED TO POSSIBLY HEAVY RAINFALL ARE LIKELY. MEANWHILE, SOME
ENHANCED RAINFALL IS POSSIBLE ALONG OR NEAR THE EAST COAST THIS
WEEKEND INTO MONDAY SHOULD A BETTER-DEFINED LOW PRESSURE CENTER
FORMS ALONG A COASTAL FRONTAL BOUNDARY. CONFIDENCE REMAINS LOW
REGARDING WHERE AND HOW MUCH RAIN COULD MOVE ONSHORE.
NEVERTHELESS, COASTAL/SOUTHEASTERN NEW ENGLAND APPEARS TO HAVE A
GREATER CHANCE OF RECEIVING THE RAIN FROM THIS SYSTEM DUE TO ITS
GEOGRAPHIC PROTRUSION INTO THE ATLANTIC. COASTAL MID-ATLANTIC MAY
ALSO SEE SOME RAIN DEPENDING ON HOW CLOSE THE LOW TRACKS TOWARD
LAND. ELSEWHERE, SOME PRECIPITATION IS ALSO BE POSSIBLE ACROSS
THE HIGHER ELEVATION OF ARIZONA INTO NEW MEXICO DURING THE WEEKEND
WITH THE PASSAGE OF THE SOUTHERN STREAM LOW.
TEMPERATURES ARE LIKELY TO BE WARMER THAN AVERAGE ACROSS THE
MID-SECTION OF THE COUNTRY UP INTO THE GREAT LAKES FOR THE WEEKEND
UNDER A BROAD AND DEEP SOUTHERLY FLOW STRENGTHENING AHEAD OF THE
DEVELOPING WESTERN UPPER TROUGH. HIGHS AND LOWS OF 10-20F ABOVE
NORMAL, WITH SOME SPOTS HIGHER, WILL BE WIDESPREAD. 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
HAZARDS:
- HIGH WINDS ACROSS PORTIONS OF THE CENTRAL AND NORTHERN PLAINS,
SUN-MON, OCT 23-OCT 24.
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE NORTHERN PLAINS,
SUN-MON, OCT 23-OCT 24.
- HEAVY RAIN ACROSS PORTIONS OF THE MISSISSIPPI VALLEY AND
SOUTHERN PLAINS, MON, OCT 24.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHEAST.
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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