913
FXUS02 KWBC 111901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT TUE OCT 11 2022
VALID 12Z FRI OCT 14 2022 - 12Z TUE OCT 18 2022
..PATTERN OVERVIEW
GUIDANCE GENERALLY AGREES UPON AN AMPLIFIED UPPER PATTERN DURING
THE PERIOD, WITH ONE RIDGE MOVING INTO THE NORTHWEST U.S./WESTERN
CANADA FROM THE EASTERN PACIFIC AND ANOTHER OVER THE NORTH
ATLANTIC HOLDING A MEAN TROUGH OVER THE EASTERN HALF OF NORTH
AMERICA. AN UPPER LOW INITIALLY OFFSHORE SOUTHERN CALIFORNIA
SHOULD EVENTUALLY DRIFT INTO THE SOUTHWEST WHILE AN UPSTREAM
TROUGH LIKELY SPLITS JUST OFF THE WEST COAST DURING THE FIRST HALF
OF NEXT WEEK. THE MOST ACTIVE WEATHER WILL BE ASSOCIATED WITH
WAVY FRONTAL SYSTEMS ON THE SOUTHERN/EASTERN SIDE OF THE MEAN
TROUGH, AS WELL AS AHEAD OF THE UPPER LOW THAT MOVES INTO THE
SOUTHWEST. MULTIPLE PERIODS OF LAKE EFFECT PRECIPITATION ARE ALSO
LIKELY GIVEN THE COMBINED MEAN TROUGH ALOFT AND CHILLY CYCLONIC
FLOW BEHIND INDIVIDUAL SURFACE WAVES/FRONTAL SYSTEMS. THE
FORECAST PATTERN WILL SUPPORT UNSEASONABLY WARM TEMPERATURES OVER
THE NORTHWEST, WHILE A BROADER AREA OF WELL BELOW NORMAL
TEMPERATURES SHOULD REACH THE EASTERN HALF OF THE COUNTRY INTO
SOUTHERN ROCKIES/HIGH PLAINS EARLY NEXT WEEK VERSUS THE LESS
EXTREME ANOMALIES FORECAST OVER THE UPPER MIDWEST INTO GREAT
LAKES/OHIO VALLEY AT THE END OF THIS WEEK.
..MODEL AND PREDICTABILITY ASSESSMENT
THE LARGE SCALE PATTERN HAS GOOD AGREEMENT AS WELL AS INTERNAL
CONSISTENCY RELATIVE TO TELECONNECTIONS ON THE STRONGEST HEIGHT
ANOMALY CENTERS, SUGGESTING GOOD PREDICTABILITY OF THE MEAN FLOW.
HOWEVER THERE ARE NOTABLE DIFFERENCES FOR ONE OR MORE IMPORTANT
BUT LOWER-PREDICTABILITY SHORTWAVES WITHIN THE EASTERN UPPER
TROUGH AS WELL AS FOR THE UPPER LOW MOVING INTO THE SOUTHWEST AND
SHORTWAVE ENERGY APPROACHING THE WEST COAST. THE 12Z GFS HAS
STRAYED A BIT ON THE FAST SIDE WITH THE LEADING FRONT CROSSING NEW
ENGLAND DURING FRIDAY-SATURDAY AND ALSO HAS A STRONGER EMBEDDED
WAVE. LARGER SCALE DIFFERENCES DEVELOP WITH THE TRAILING
SHORTWAVES/SURFACE FRONTS, WITH GFS RUNS GENERALLY ON THE FAST
SIDE AND ECMWF TENDING TO BE THE SLOWEST (BUT THE NEW 12Z ECMWF
HAS ADJUSTED SOMEWHAT FASTER). INTERESTINGLY, THE 12Z UKMET/CMC
AND 00Z ECMWF BECOME A LITTLE FASTER THAN THE GFS AND 12Z GEFS/00Z
ECENS FOR THE SOUTHWEST UPPER LOW. THE NEW 12Z ECMWF HAS ADJUSTED
A LITTLE SLOWER HERE AS WELL. MEANWHILE RECENT TRENDS ARE MIXED
FOR WHERE THE SOUTHERN STREAM COMPONENT OF SPLITTING EASTERN
PACIFIC SHORTWAVE ENERGY WILL END UP BY EARLY NEXT WEEK.
GIVEN THE LOWER PREDICTABILITY ELEMENTS WITHIN THE MORE CONFIDENT
MEAN PATTERN, PREFERENCE SIDED WITH AN INTERMEDIATE SOLUTION WHERE
DIFFERENCES EXISTED. THUS THE UPDATED FORECAST STARTED WITH AN
OPERATIONAL MODEL COMPOSITE FOR ABOUT THE FIRST HALF OF THE PERIOD
AND TRANSITIONED TO A MODEL/MEAN BLEND THEREAFTER. IN TERMS OF
QPF, AMOUNTS WERE RAISED FROM THE NBM ACROSS THE GREAT LAKES TO
BETTER ACCOUNT FOR LAKE EFFECT PRECIP AND INCREASED LIGHT AMOUNTS
IN OTHER PARTS OF THE EAST-CENTRAL U.S. TO ACCOUNT FOR THE
TYPICALLY LOW NBM BIAS FOR SUCH AMOUNTS AND INTERMEDIATE FRONTAL
TIMING.
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
THE FIRST STRONG COLD FRONT ASSOCIATED WITH THE LONG-TERM UPPER
TROUGH WILL BRING MODERATE TO LOCALLY HEAVY RAIN ACROSS CENTRAL
AND EASTERN NEW ENGLAND ON FRIDAY, WITH THE POTENTIAL FOR SOME 2+
INCH TOTALS. GUIDANCE IS GRADUALLY IMPROVING ITS SIGNAL FOR HEAVY
RAINFALL POTENTIAL BY WAY OF AT LEAST PLUS 2-2.5 STANDARD
DEVIATIONS FOR PRECIPITABLE WATER VALUES AND A GENERAL PATTERN
FAVORABLE FOR BANDS OF RAIN THAT COULD EXHIBIT SOME TRAINING.
THIS SCENARIO MAY BE SUFFICIENT TO COUNTER RECENTLY DRY CONDITIONS
SO THE EXPERIMENTAL DAY 4 EXCESSIVE RAINFALL OUTLOOK HAS
INTRODUCED A COORDINATED SLIGHT RISK AREA THAT INCORPORATES ABOUT
THE SOUTHERN/EASTERN THREE-FOURTHS OF MAINE. NEGATIVE TILT OF THE
UPPER TROUGH AND THE TIGHT SURFACE PRESSURE GRADIENT MAY SUPPORT
STRONG AND GUSTY WINDS AS WELL. TO THE WEST, LAKE ENHANCED RAIN
AND SNOW SHOWERS ARE LIKELY ACROSS THE GREAT LAKES FOR THE FRIDAY
THROUGH SATURDAY TIME PERIOD. SHOWERS COULD BECOME MORE
WIDESPREAD LATE WEEKEND INTO NEXT WEEK WITH ANOTHER FRONTAL SYSTEM
AND TRAILING COLD CYCLONIC LOW LEVEL FLOW. TIMING DIFFERENCES IN
THE GUIDANCE FOR THIS LATTER FRONT KEEP CONFIDENCE FAIRLY LOW FOR
RAINFALL AMOUNTS/COVERAGE OVER THE EASTERN U.S. EARLY NEXT WEEK,
RANGING BETWEEN FAIRLY MODEST TO SIGNIFICANT. MEANWHILE SHOWERS
AND THUNDERSTORMS WILL LIKELY INCREASE IN COVERAGE OVER THE
SOUTHWEST AND THEN INTO TEXAS FROM SUNDAY INTO EARLY NEXT WORK
WEEK, AS THE UPPER LOW TRACKING INTO THE REGION FROM THE PACIFIC
SPREADS MOISTURE OUT TO ITS EAST. SOME OF THIS MOISTURE MAY
INTERACT WITH A COUPLE FRONTS FORECAST TO DROP SOUTHWARD OVER THE
PLAINS.
MUCH OF THE NORTHWESTERN U.S. AS WELL AS NORTHERN CALIFORNIA INTO
PARTS OF THE GREAT BASIN SHOULD HAVE ABOVE NORMAL TEMPERATURES
EACH DAY WITH THE UPPER RIDGE ANCHORED OVER OR NEAR THE REGION,
WITH SOME HIGHS REACHING 10-15F ABOVE NORMAL. ON THE OTHER HAND,
A SERIES OF FRONTS PUSHED ALONG WITHIN/AROUND THE EASTERN UPPER
TROUGH WILL BRING PROGRESSIVELY COLDER TEMPERATURES TO AREAS EAST
OF THE ROCKIES. LATE THIS WEEK THE COOLEST ANOMALIES (UP TO
10-15F BELOW NORMAL) SHOULD EXTEND FROM THE UPPER MIDWEST INTO
GREAT LAKES/OHIO VALLEY. THEN EXPECT INCREASING COVERAGE OF HIGHS
10-20F BELOW NORMAL (LOWS 5-15F BELOW NORMAL) OVER THE
MIDWEST/EAST NEXT MONDAY-TUESDAY. THE SOUTHERN PLAINS AND
VICINITY WILL BE QUITE WARM FRIDAY-SATURDAY BUT THEN THE REGION
(INTO THE SOUTHERN ROCKIES) WILL TREND COLDER AS RAINFALL SPREADS
ACROSS THE REGION.
RAUSCH/HAMRICK
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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