302
FXUS02 KWBC 310700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT MON OCT 31 2022
VALID 12Z THU NOV 03 2022 - 12Z MON NOV 07 2022
...WESTERN-CENTRAL U.S. SYSTEM TO BRING HEAVY MOUNTAIN SNOW TO
PARTS OF THE GREAT BASIN/ROCKIES AND HEAVY RAIN POTENTIAL TO
PORTIONS OF THE PLAINS...
...LATE WEEK ATMOSPHERIC RIVER EVENT LIKELY TO BRING AN EPISODE OF
HEAVY PRECIPITATION TO PARTS OF THE NORTHWEST...
..OVERVIEW
EXPECT AN AMPLIFIED PATTERN TO PREVAIL DURING LATE THIS WEEK INTO
THE EARLY WEEKEND AS A DEEP TROUGH CARRIES AN EMBEDDED UPPER LOW
ACROSS SOUTHERN PARTS OF THE WEST AND STRONG RIDGING BUILDS OVER
THE EAST. MEANWHILE STRONG NORTH PACIFIC FLOW WILL INITIALLY
EXTEND INTO SOUTHWESTERN CANADA AND THEN SAG SOUTHWARD INTO THE
NORTHWEST U.S. ONCE THIS PACIFIC JET REACHES FAR ENOUGH SOUTH
AFTER EARLY SATURDAY, IT SHOULD ACCELERATE THE UPPER LOW
PROGRESSING EASTWARD/NORTHEASTWARD ACROSS AND BEYOND THE PLAINS.
BY LATE WEEKEND INTO EARLY NEXT WEEK THE PATTERN SHOULD TAKE ON A
MORE ZONAL OR BROADLY CYCLONIC LOOK AS EAST-WEST TROUGHING EVOLVES
OVER THE WESTERN HALF OF CANADA IN RESPONSE TO STRONG ALASKA
RIDGING WHILE THE EAST COAST RIDGE MOVES INTO THE ATLANTIC. THE
LEADING WESTERN SYSTEM WILL INITIALLY SUPPORT MEANINGFUL
RAIN/MOUNTAIN SNOW OVER PARTS OF THE FOUR CORNERS STATES AND THEN
A HEAVY RAIN THREAT OVER THE SOUTH-CENTRAL PLAINS, WHILE THE
NORTHWEST ATMOSPHERIC RIVER EVENT SHOULD BE MOST PRONOUNCED AROUND
FRIDAY-FRIDAY NIGHT WITH A GRADUALLY LIGHTER TREND THEREAFTER.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
IN THE GUIDANCE THROUGH THE 12Z/18Z CYCLE, THERE WERE STILL
DISCREPANCIES WITH THE ULTIMATE TIMING OF THE UPPER LOW
PROGRESSING THROUGH THE SOUTHERN ROCKIES AND THEN CONTINUING
NORTHEASTWARD. MOST OF THESE DIFFERENCES CORRESPONDED TO
DIFFERENCES IN THE POSITION AND ORIENTATION OF THE PACIFIC JET
COMING INTO NORTH AMERICA. GFS RUNS TENDED TO BE ON THE SLOWER
SIDE OF THE SPECTRUM FOR THE UPPER LOW DUE TO BEING MORE
WESTERLY/NORTHWARD WITH THE PACIFIC JET. ON THE OTHER HAND THE
12Z ECMWF STRAYED TO THE FAST SIDE AFTER LATE SATURDAY DUE TO A
FARTHER SOUTH PACIFIC JET WITH A BIT MORE OF A NORTHWESTERLY TILT.
RECENT GEFS MEANS HAVE AT LEAST BEEN SUGGESTING THOSE OPERATIONAL
GFS RUNS COULD BE TOO SLOW WITH THE UPPER LOW. IN ORDER TO
MAINTAIN THE BEST CONTINUITY POSSIBLE UNTIL GUIDANCE SHIFTS ENOUGH
TO SUGGEST A MORE CONFIDENT CHANGE FOR THE UPPER LOW AND INCOMING
PACIFIC FLOW, THE UPDATED FORECAST TRANSITIONED TOWARD A BLEND OF
THE 12Z CMC AND 00Z/30 ECMWF (WHICH WAS SLOWER THAN THE 12Z RUN,
MORE IN LINE WITH THE 12Z CMC) ALONG WITH THE 18Z GEFS/12Z ECMWF
MEANS BY DAYS 6-7 SUNDAY-MONDAY. THE FIRST HALF OF THE PERIOD
FEATURED GOOD ENOUGH CLUSTERING TO ALLOW FOR AN OPERATIONAL MODEL
COMPOSITE. THE NEW 00Z GFS HAS TRENDED FAVORABLY FASTER FOR THE
UPPER LOW IN RESPONSE TO ADJUSTING CLOSER TO CONSENSUS FOR
INCOMING PACIFIC FLOW. THE CMC HAS ADJUSTED SOMEWHAT FASTER THAN
ITS PREVIOUS RUN AFTER SATURDAY WHILE THE ECMWF REMAINS THE
FASTEST SOLUTION (WITH A DEEP UPPER MIDWEST STORM IN THE PROCESS).
THIS YIELDS A GUIDANCE AVERAGE THAT IS NOW SOMEWHAT FASTER THAN
PRIOR PREFERENCE.
PREDICTABILITY OF WESTERN U.S. FLOW DETAILS WOULD APPEAR TO START
DECLINING APPRECIABLY LATE IN THE PERIOD AND THEREAFTER, AS
GUIDANCE DIVERGES ON SPECIFICS OF UPPER RIDGING THAT BUILDS
OVER/NEAR ALASKA. AS SEEN IN PREVIOUS CASES, ISSUES REGARDING
WHETHER THE ALASKA RIDGE CLOSES OFF AND ITS ULTIMATE PATH IF IT
DOES, CAN CAUSE HAVOC WITH THE FORECAST OVER THE EASTERN PACIFIC
AND DOWNSTREAM INTO THE LOWER 48.
..WEATHER/HAZARD HIGHLIGHTS
THE INITIAL WESTERN U.S. UPPER TROUGH AND EMBEDDED LOW TRACKING
ACROSS SOUTHERN PARTS OF THE WEST WILL INITIALLY BRING MOUNTAIN
SNOW AND LOWER ELEVATION RAIN TO THE GREAT BASIN AND CENTRAL
ROCKIES, WITH SOME PRECIPITATION EXTENDING FARTHER SOUTH AS WELL.
WPC WINTER WEATHER OUTLOOK PROBABILITIES REFLECT AREAS WITH THE
BEST POTENTIAL FOR MEANINGFUL TO HEAVY MOUNTAIN SNOW OVER THIS
REGION. EXPECT RAIN INCREASE IN COVERAGE AND INTENSITY OVER THE
CENTRAL U.S. LATE IN THE WEEK AND PERSIST INTO THE WEEKEND AS THE
WESTERN SYSTEM APPROACHES. SOME RAIN MAY BECOME HEAVY AND STRONG
CONVECTION IS POSSIBLE AS WELL. THE EXPERIMENTAL DAY 5 EXCESSIVE
RAINFALL OUTLOOK CURRENTLY DEPICTS A SLIGHT RISK AREA FROM
PORTIONS OF SOUTHERN KANSAS INTO NORTHERN TEXAS FOR THE EARLY
FRIDAY INTO EARLY SATURDAY TIME FRAME. THIS EVENT MAY FEATURE A
COMBINATION OF FLASH FLOOD THREATS 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. RAINFALL SHOULD TREND LIGHTER
AND MORE PROGRESSIVE FROM LATE WEEKEND INTO EARLY NEXT WEEK AS THE
SUPPORTING UPPER LOW ACCELERATES NORTHEASTWARD.
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 (LIKEWISE PUSHING THE
PRECIPITATION SHIELD GRADUALLY FARTHER SOUTH) SHOULD BE SUFFICIENT
TO ALLOW FOR A LIGHTER TREND. A PERIOD OF STRONG WINDS WILL BE
POSSIBLE IN THIS EVENT AS WELL. SOMEWHAT LESS EXTREME BUT STILL
SIGNIFICANT PRECIPTATION WILL REACH INTO THE NORTHERN ROCKIES.
THE WEST WILL SEE A BROAD AREA OF DAYTIME HIGHS 10-20F OR SO BELOW
NORMAL UNDER THE FORECAST UPPER TROUGH/LOW THROUGH FRIDAY. SOME
AREAS OVER OR NEAR SOUTHERN CALIFORNIA MAY SEE RECORD COLD HIGHS.
DOUBLE-DIGIT ANOMALIES SHOULD BECOME MUCH MORE SCATTERED DURING
THE WEEKEND AS TEMPERATURES MODERATE BUT MOST AREAS SHOULD REMAIN
NEAR TO 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, POSSIBLY
BRINGING HIGHS DOWN TO 20-30F BELOW NORMAL OVER MONTANA. ON THE
OTHER HAND, WELL ABOVE NORMAL TEMPERATURES WILL PREVAIL OVER MOST
AREAS EAST OF THE ROCKIES THROUGH ABOUT THURSDAY AND THEN THE
PLAINS WILL LIKELY TREND COOLER WHILE THE MISSISSIPPI VALLEY AND
ESPECIALLY EAST REMAIN WARM. DURING THURSDAY-EARLY FRIDAY THE
WARMEST ANOMALIES (PLUS 10-25F) SHOULD BE FROM THE UPPER MIDWEST
INTO CENTRAL PLAINS WHILE AREAS FROM THE GREAT LAKES/OHIO VALLEY
INTO NORTHEAST SHOULD SEE MULTIPLE DAYS WITH TEMPERATURES 10-20F
ABOVE NORMAL DURING THE PERIOD.
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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