050
FXUS02 KWBC 020701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT WED NOV 02 2022
VALID 12Z SAT NOV 05 2022 - 12Z WED NOV 09 2022
...SOME LINGERING HEAVY RAIN POTENTIAL WITH THE SATURDAY
MISSISSIPPI VALLEY SYSTEM/FRONT...
...CHILLY PATTERN OVER THE WEST WITH SIGNIFICANT RAIN/MOUNTAIN
SNOW OVER SOME AREAS...
..OVERVIEW
EXPECT A LEADING MISSISSIPPI VALLEY SYSTEM AS OF EARLY SATURDAY TO
EJECT RAPIDLY INTO CANADA BY SATURDAY NIGHT. AS A STRONG UPPER
RIDGE ALONG AND OFFSHORE THE EAST COAST PROVIDES RESISTANCE, A
PORTION OF THE FRONT TRAILING FROM THE SURFACE LOW TO STALL AND
EVENTUALLY LIFT NORTHWEST AS A WARM FRONT BEFORE DISSIPATING.
GUIDANCE SUGGESTS THAT THE AXIS OF AN AMPLIFIED MEAN TROUGH WILL
SETTLE NEAR THE WEST COAST, BUT WITH SOME UNCERTAINTY OVER THE
AMPLITUDE OF THIS TROUGH/PROGRESSION OF EJECTING ENERGY DUE TO
DIFFERENCES IN THE DEPICTION OF A STRONG UPPER RIDGE THAT BUILDS
OVER ALASKA AND VICINITY. AT THE VERY LEAST THIS PATTERN SHOULD
SUPPORT SEVERAL DAYS OF BELOW NORMAL TEMPERATURES ACROSS THE WEST
AND MULTIPLE EPISODES OF RAIN AND MOUNTAIN SNOW FROM THE WEST
COAST INTO THE ROCKIES. A SYSTEM EMERGING FROM THE WEST COULD
ALSO PRODUCE MEANINGFUL PRECIPITATION ACROSS PARTS OF THE NORTHERN
TIER DURING THE FIRST HALF OF NEXT WEEK.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
THE MODELS AND MEANS ARE STILL NUDGING A LITTLE FASTER FOR THE
INITIAL MISSISSIPPI VALLEY SYSTEM AND ASSOCIATED FRONTS, BUT
RUN-TO-RUN CHANGES SEEM TO BE GETTING A LITTLE LESS PRONOUNCED
WITH TIME AND CLUSTERING IS GRADUALLY IMPROVING AS WELL. AN
OPERATIONAL MODEL COMPOSITE HANDLED THIS SYSTEM WELL, ACCOUNTING
FOR LINGERING DETAIL SPREAD AND UNCERTAINTY.
THE PRIMARY LARGE SCALE ISSUE BEHIND THIS SYSTEM IS HOW AMPLIFIED
THE WEST COAST TROUGH BECOMES ALONG WITH THE SPECIFICS OF ENERGY
ROUNDING THE TROUGH AND EJECTING DOWNSTREAM DURING THE FIRST HALF
OF NEXT WEEK. AMONG THE 12Z/18Z RUNS, THESE DIFFERENCES BECAME
NOTICEABLE BY DAY 5 MONDAY WITH THE GFS/GEFS STARTING TO BECOME
MORE AMPLIFIED THAN MOST OTHER MODELS TO VARYING DEGREES. THIS
LEADS TO THE EMBEDDED UPPER LOW OFF VANCOUVER ISLAND OR THE
PACIFIC NORTHWEST COAST TRACKING FARTHER SOUTH BY LATE IN THE
PERIOD. IN ADDITION GREATER RIDGING DOWNSTREAM LED TO SLOWER
PROGRESSION OF EJECTING SHORTWAVE ENERGY AND ASSOCIATED SURFACE
SYSTEM EARLY-MID WEEK. THESE DIFFERENCES CORRESPONDED TO THE
GFS/GEFS DEPICTING A WEAKER/MORE OPEN ALASKA RIDGE COMPARED TO THE
MAJORITY. SUCH ISSUES WITH ALASKA RIDGING IN THE COLD SEASON TEND
TO LOWER PREDICTABILITY DOWNSTREAM. THUS PREFERRED TILTING AT
LEAST TWO-THIRDS TOWARD THE MAJORITY SCENARIO WHICH IS CLOSER TO
CONTINUITY, BY WAY OF MORE 12Z ECMWF/ECMWF MEAN WEIGHT RELATIVE TO
THE 18Z GFS/GEFS MEAN. AS SEEMINGLY CONFIRMED BY THE NEW 00Z RUN,
THE 12Z CMC BECAME SUSPICIOUSLY AMPLIFIED WITH ITS EAST-CENTRAL
U.S. SHORTWAVE BY NEXT WEDNESDAY AND THUS ITS INPUT WAS MINIMIZED
LATE. THE NEW 00Z ECMWF, AS WELL AS THE UKMET THROUGH THE END OF
ITS RUN, NOW SHIFT THE BALANCE OF SOLUTIONS MORE IN THE GFS
DIRECTION--HIGHLIGHTING THE ONGOING UNCERTAINTY.
FINALLY, DETAILS CONTINUE TO FLUCTUATE WITHIN A MORE BROADLY
AGREEABLE UPPER LOW EXPECTED TO WOBBLE FROM NEAR THE EASTERN
BAHAMAS TOWARD THE SOUTHEASTERN U.S. COAST (WITH ACCOMPANYING
SURFACE LOW/TROUGH). SPECIFICS WILL DEPEND IN PART ON THE
UNCERTAIN DETAILS OF FLOW TO THE WEST. A BLEND APPROACH APPEARS
REASONABLE FOR DEPICTING THIS FEATURE.
..WEATHER/HAZARD HIGHLIGHTS
THE LEADING SYSTEM TRACKING NORTHEASTWARD FROM THE MISSISSIPPI
VALLEY ON SATURDAY, ALONG WITH ITS ASSOCIATED FRONTS, WILL PRODUCE
SOME LOCALLY MODERATE TO HEAVY RAINFALL BUT LIKELY WITH LOWER
TOTALS THAN EXPECTED DURING FRIDAY-FRIDAY NIGHT. AREAS OF INTEREST
FOR ENHANCED RAINFALL WILL BE OVER THE UPPER MIDWEST/UPPER GREAT
LAKES NEAR THE SURFACE LOW TRACK AS WELL AS OVER/NEAR THE LOWER
MISSISSIPPI VALLEY AS THE TRAILING FRONT DECELERATES.
AREAS FROM THE WEST COAST INTO THE NORTHERN HALF OF THE ROCKIES
SHOULD SEE MULTIPLE EPISODES OF RAIN AND HIGHER ELEVATION SNOW,
WITH SNOW LEVELS TENDING TO DECLINE WITH TIME AS THE MEAN TROUGH
ALOFT NEAR THE WEST COAST AMPLIFIES. UNCERTAINTY OVER THE PRECISE
AMPLITUDE OF THE TROUGH LOWERS CONFIDENCE IN THE PRECISE FOCUS OF
HIGHEST TOTALS BUT THE BEST SIGNAL AT THE MOMENT IS GENERALLY OVER
SOUTHERN OREGON AND NORTHERN CALIFORNIA. MULTIPLE SYSTEMS MAY
PROVIDE ADDED FOCUS. THESE INCLUDE A FRONT REACHING THE NORTHWEST
BY SATURDAY AND A SYSTEM APPROACHING THE NORTHWEST ON SUNDAY. ANY
POTENTIAL SYSTEMS NEXT WEEK HAVE LOWER CONFIDENCE. THIS LOWER
CONFIDENCE EXTENDS TO ANY LOW PRESSURE THAT MAY EXTEND INTO THE
PLAINS WITH AN AREA OF SNOW OR RAIN DEPENDING ON TRACK/EVOLUTION.
MOISTURE SHOULD EVENTUALLY INCREASE NEAR THE EAST COAST NEXT WEEK
AS THE UPPER LOW INITIALLY OVER THE EASTERN BAHAMAS RETROGRADES
TOWARD THE SOUTHEASTERN U.S./FLORIDA.
AFTER A BRIEF REBOUND TO ONLY MODERATELY BELOW NORMAL TEMPERATURES
OVER THE WEST DURING THE WEEKEND, THE FORECAST OF AN AMPLIFYING
UPPER TROUGH NEXT WEEK SHOULD EXPAND THE COVERAGE OF HIGHS 10-20F
BELOW NORMAL ACROSS THE WEST ONCE AGAIN. COLDEST AIR SHOULD EXTEND
FROM WESTERN CANADA INTO MONTANA WITH SOME HIGHS IN THAT STATE
20-35F BELOW NORMAL MONDAY-WEDNESDAY. IN CONTRAST TO THE SOMEWHAT
WINTER-LIKE TEMPERATURES OVER THE WEST, THE EAST WILL SEE
TEMPERATURES MORE TYPICAL FOR EARLIER IN THE FALL WITH A BROAD
AREA OF PLUS 10-25F ANOMALIES, ESPECIALLY SATURDAY-MONDAY WHEN
DAILY RECORDS SHOULD BE MOST NUMEROUS. ANOMALIES SHOULD BE A
LITTLE MORE EXTREME FOR MORNING LOWS VERSUS DAYTIME HIGHS. PLUS
10-20F READINGS SHOULD BE MORE COMMON BY TUESDAY-WEDNESDAY.
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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