105
FXUS02 KWBC 010700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT TUE NOV 01 2022
VALID 12Z FRI NOV 04 2022 - 12Z TUE NOV 08 2022
...SYSTEM EMERGING FROM THE ROCKIES TO BRING A POTENTIAL FOR HEAVY
RAIN TO PORTIONS OF THE PLAINS...
...LATE WEEK ATMOSPHERIC RIVER EVENT LIKELY TO BRING AN EPISODE OF
HEAVY PRECIPITATION TO PARTS OF THE NORTHWEST...
..OVERVIEW
GUIDANCE CONTINUES TO SHOW AN AMPLIFIED PATTERN LATE THIS WEEK
INTO THE EARLY WEEKEND AS AN UPPER TROUGH AND EMBEDDED LOW MOVES
FROM THE ROCKIES INTO THE PLAINS AND A STRONG RIDGE BUILDS NEAR
THE EAST COAST. STRONG NORTH PACIFIC FLOW PUSHING INTO WESTERN
NORTH AMERICA WILL HELP TO ACCELERATE THE PLAINS SYSTEM
NORTHEASTWARD, DEFLECTED BY THE EAST COAST RIDGE THAT WILL BECOME
CENTERED OVER THE WESTERN ATLANTIC. IN RESPONSE TO A STRONG UPPER
RIDGE THAT BUILDS OVER AND NEAR ALASKA, BY SUNDAY-TUESDAY THE MEAN
PATTERN OVER THE EASTERN PACIFIC THROUGH WESTERN TWO-THIRDS OF THE
LOWER 48 SHOULD BECOME BROADLY CYCLONIC. THE LEADING PLAINS SYSTEM
WILL SUPPORT A HEAVY RAIN THREAT OVER PARTS OF THE CENTRAL U.S.
LATE THIS WEEK INTO THE EARLY WEEKEND. MEANWHILE THE NORTHWEST
ATMOSPHERIC RIVER EVENT SHOULD BE MOST PRONOUNCED AROUND
FRIDAY-FRIDAY NIGHT, WITH THE PATTERN POTENTIALLY SUPPORTING
MULTIPLE DAYS OF LESS EXTREME BUT STILL MEANINGFUL RAIN/MOUNTAIN
SNOW OVER THE WEST THEREAFTER.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
THE MODELS CONTINUE TO SHOW A FAIR AMOUNT OF SPREAD AND TRENDING
FOR THE SPECIFICS OF THE UPPER TROUGH/EMBEDDED LOW EJECTING
THROUGH THE PLAINS AND BEYOND DURING THE WEEKEND. IN THE 12Z
GUIDANCE THERE WAS A NEW WRINKLE COMPARED TO PREVIOUS CYCLES AS
THE ECMWF/UKMET DEPICTED A MORE ELONGATED AND FARTHER NORTH LOW
FOR A TIME. GFS RUNS THROUGH 18Z WERE STILL ON THE SLOWER SIDE OF
THE SPREAD, JOINED BY THE 12Z CMC, BUT THE LATTER BECAME A
PRONOUNCED SOUTHERN EXTREME WITH THE UPPER LOW FROM SUNDAY ONWARD.
NEW 00Z RUNS GENERALLY ADD TO THE FASTER TREND AND THE 00Z CMC
EVOLUTION IS NOW MUCH CLOSER TO OTHER GUIDANCE. BASED ON THE
12Z/18Z GUIDANCE AND ONGOING UNCERTAINTY, AN OPERATIONAL MODEL
COMPOSITE PROVIDED A REASONABLE FASTER ADJUSTMENT FROM PREVIOUS
FORECAST BUT THE NEXT ISSUANCE REFLECTING NEWEST SOLUTIONS WILL
LIKELY BE FASTER YET.
AS UPPER RIDGING BUILDS TOWARD AND INTO ALASKA, LATEST CONSENSUS
SHOWS AN UPPER LOW/TROUGH DROPPING DOWN FROM THE GULF OF ALASKA
TOWARD VANCOUVER ISLAND AND PACIFIC NORTHWEST DURING THE
WEEKEND--SUPPORTING A LEADING SURFACE SYSTEM THAT PUSHES INTO THE
NORTHWEST. LATEST GFS/ECMWF/CMC RUNS ALL SUGGEST THAT THE UPPER
TROUGH ENERGY SHOULD CONTINUE EASTWARD AND BRING LOW PRESSURE INTO
THE PLAINS/UPPER MIDWEST TOWARD THE END OF THE PERIOD NEXT
TUESDAY. THIS SYSTEM IS A RELATIVELY NEW FEATURE IN THE GUIDANCE
AND THE GEFS MEAN THUS FAR BARELY HINTS AT IT. THE 12Z
ECENS/CMCENS MEANS HAD A WEAK BUT DEFINED WAVE AS OF EARLY
TUESDAY. ENOUGH SIGNAL EXISTS TO DEPICT THE SYSTEM, BUT FOR NOW IN
FAIRLY CONSERVATIVE FORM BY WAY OF A COMBINATION OF THE 18Z
GFS/12Z ECMWF AND THEIR MEANS. IN SPITE OF THE RELATIVE AGREEMENT
IN PRINCIPLE AT THE MOMENT, IT SHOULD BE NOTED THAT THE FULL
ENSEMBLE SPREAD FOR THE EASTERN PACIFIC/LOWER 48 PATTERN BECOMES
QUITE BROAD BY NEXT MONDAY-TUESDAY. THIS SEEMS TO REFLECT THE
SIGNIFICANTLY LOWER PREDICTABILITY OF THE EASTERN PACIFIC/LOWER 48
PATTERN THAT CAN RESULT FROM TYPICAL UNCERTAINTY OVER THE DETAILS
OF ANY UPPER RIDGE BUILDING OVER ALASKA DURING THE COOL SEASON.
..WEATHER/HAZARD HIGHLIGHTS
THE LEADING SYSTEM EMERGING FROM THE ROCKIES INTO THE PLAINS WILL
BRING AN EPISODE OF HEAVY RAIN POTENTIAL TO PARTS OF THE CENTRAL
U.S. LATE THIS WEEK AND INTO THE WEEKEND. SOME STRONG CONVECTION
IS POSSIBLE OVER PARTS OF THE PLAINS AS WELL, PER THE LATEST
OUTLOOKS FROM THE STORM PREDICTION CENTER. THE EXPERIMENTAL DAY 4
EXCESSIVE RAINFALL OUTLOOK REFLECTS THE BEST POTENTIAL FOR
HEAVIEST RAINFALL DURING FRIDAY-FRIDAY NIGHT, OVER AND JUST EAST
OF PORTIONS OF THE SOUTH-CENTRAL PLAINS. A BAND OF MODERATE TO
HEAVY RAINFALL MAY DEVELOP ALONG A FRONT EXTENDING NORTHWARD INTO
THE MIDWEST AS WELL. HEAVY RAINFALL SHOULD BECOME LESS WIDESPREAD
OVER THE COURSE OF THE WEEKEND AS THE SUPPORTING DYNAMICS LIFT
NORTHEASTWARD. THE PORTION OF THE SURFACE FRONT STALLING OVER THE
LOWER MISSISSIPPI VALLEY MAY PROVIDE THE BEST FOCUS FOR LINGERING
AREAS OF SIGNIFICANT RAINFALL. THIS EVENT MAY FEATURE A
COMBINATION OF FLASH FLOOD THREATS (IN MAINLY URBANIZED/METRO
REGIONS) WHERE THE HEAVIEST RAIN OCCURS BUT ALSO BENEFICIAL
RAINFALL GIVEN THE LONG-TERM DROUGHT OVER THE REGION. MONITOR
STORM PREDICTION CENTER OUTLOOKS FOR LATEST INFORMATION ON SEVERE
POTENTIAL.
THE OTHER SIGNIFICANT PRECIPITATION FOCUS WILL BE OVER THE
NORTHWEST LATE THIS WEEK INTO THE WEEKEND, DUE TO AN ATMOSPHERIC
RIVER EVENT ASSOCIATED WITH STRONG WESTERLY FLOW REACHING INTO THE
REGION. A PERIOD OF HEAVY RAIN/MOUNTAIN SNOW APPEARS LIKELY WITH
HIGHEST TOTALS TENDING TO BE DURING FRIDAY-FRIDAY NIGHT. SOME
SIGNIFICANT PRECIPITATION SHOULD CONTINUE INTO THE WEEKEND BUT THE
SOUTHWARD PROGRESSION OF THE PACIFIC JET (EXTENDING THE
PRECIPITATION SHIELD GRADUALLY FARTHER SOUTH) SHOULD BE SUFFICIENT
TO ALLOW FOR A SOMEWHAT LIGHTER TREND. A PERIOD OF STRONG WINDS
WILL BE POSSIBLE IN THIS EVENT AS WELL. SOMEWHAT LESS EXTREME BUT
STILL SIGNIFICANT PRECIPITATION WILL REACH INTO THE NORTHERN
ROCKIES. THE PATTERN MAY SUPPORT CONTINUATION OF SOME
PRECIPITATION OVER THE NORTHERN HALF OF THE WEST THROUGH THE FIRST
HALF OF NEXT WEEK. SNOW LEVELS OVER FAR NORTHERN AREAS MAY TREND
NOTABLY LOWER DEPENDING ON THE SOUTHWARD EXTENT OF COLD AIR
PUSHING DOWN FROM WESTERN CANADA.
CONFIDENCE IS NOT VERY HIGH THUS FAR, BUT GUIDANCE SUGGESTS THAT A
SYSTEM REACHING THE NORTHWEST LATE IN THE WEEKEND MAY LEAD TO
PLAINS/UPPER MIDWEST LOW PRESSURE BY NEXT TUESDAY. THIS SYSTEM
COULD PRODUCE SOME SNOW OVER THE NORTHER TIER. NEAR THE EAST
COAST, BY VERY LATE IN THE PERIOD SOME MOISTURE COULD APPROACH
FROM THE ATLANTIC AS AN UPPER LOW NEAR THE BAHAMAS RETROGRADES
TOWARD FLORIDA.
THE SOUTHERN THREE-FOURTHS OF THE WEST WILL SEE A BROAD AREA OF
DAYTIME HIGHS 10-25F BELOW NORMAL CONTINUE THROUGH FRIDAY.
DOUBLE-DIGIT ANOMALIES SHOULD BECOME MORE SCATTERED DURING THE
WEEKEND AS TEMPERATURES MODERATE BUT MOST AREAS SHOULD REMAIN
BELOW NORMAL FOR HIGHS. THE EVOLVING UPPER PATTERN SHOULD SUPPORT
A PUSH OF COLD AIR REACHING THE NORTHERN HIGH PLAINS/EASTERN
SLOPES OF THE ROCKIES BY NEXT MONDAY-TUESDAY, POSSIBLY PUSHING
HIGHS DOWN TO 20-35F BELOW NORMAL OVER MONTANA. PERSISTENCE OF
MEAN TROUGHING ALOFT TO SOME DEGREE SHOULD KEEP THE WEST BELOW
NORMAL EARLY NEXT WEEK WITH MINUS 5-15F ANOMALIES FOR HIGHS. WHILE
IT WILL FEEL MORE LIKE WINTER OVER THE WEST, THE EAST WILL SEE
TEMPERATURES MORE TYPICAL FOR EARLIER IN THE FALL. EXPECT A BROAD
AREA OF PLUS 10-25F ANOMALIES THAT SHOULD PRODUCE SOME DAILY
RECORDS, WITH MORNING LOWS TENDING TO BE SLIGHTLY MORE EXTREME
THAN THE DAYTIME HIGHS.
RAUSCH
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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