696
FXUS02 KWBC 122037
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
436 PM EDT WED OCT 12 2022
VALID 12Z SAT OCT 15 2022 - 12Z WED OCT 19 2022
..PATTERN OVERVIEW
EXPECT A MORE ACTIVE FALL WEATHER PATTERN TO REMAIN IN PLACE OVER
MANY AREAS THROUGH THE UPCOMING WEEKEND AND NEXT WEEK AS A COUPLE
OF COLD FRONTS ASSOCIATED WITH AN AMPLIFYING EASTERN U.S. UPPER
LEVEL TROUGH (AND EMBEDDED SHORTWAVES) MOVE ACROSS THE CENTRAL AND
EASTERN STATES. THERE MAY ALSO BE SOME DEGREE OF LOW PRESSURE
DEVELOPMENT IN THE VICINITY OF NEW ENGLAND/SOUTHEASTERN CANADA
EARLY-MID WEEK. TRAILING COLDER CYCLONIC FLOW WILL SUPPORT
PERIODS OF LAKE EFFECT PRECIPITATION THAT MAY INCLUDE SNOW BY NEXT
WEEK. MEANWHILE THE MOISTURE AHEAD OF AN UPPER LOW TRACKING INTO
THE SOUTHWEST WILL PRODUCE AN AREA OF MODERATE TO HEAVY RAINFALL
ACROSS PARTS OF ARIZONA/NEW MEXICO/TEXAS FROM THE WEEKEND INTO
EARLY NEXT WEEK. IN CONTRAST TO THE INCREASINGLY COLD PATTERN
OVER THE EAST, SUMMER WILL TRY TO HANG ON A LITTLE LONGER OVER THE
NORTHWEST WHERE TEMPERATURES SHOULD REMAIN WELL ABOVE NORMAL
THROUGH THE PERIOD.
..MODEL AND PREDICTABILITY ASSESSMENT
WITHIN THE AGREEABLE LARGE SCALE PATTERN, THE PRIMARY DIFFERENCES
INVOLVED THE UPPER TROUGH/LOW AND SURFACE SYSTEM REACHING THE EAST
DURING THE LATTER HALF OF THE PERIOD (GFS ON THE FAST SIDE BUT A
BIT LESS EXTREME IN THE NEW 12Z RUN, WHILE THE ECMWF HAS NUDGED A
BIT FASTER THAN RUNS FROM A DAY OR SO AGO) ALONG WITH TIMING OF
THE SOUTHWEST UPPER LOW AND ITS EVENTUAL WEAKENING (GFS FASTER
THAN THE MAJORITY, INCLUDING THE GEFS MEAN, THOUGH EVEN THE 00Z
ECMWF WAS A LITTLE FASTER THAN THE GEFS/ECENS). GFS/ECMWF RUNS
AND THEIR MEANS ARE SIMILAR FOR THE UPPER LOW THAT SETTLES
OFFSHORE FROM CALIFORNIA LATE IN THE PERIOD AFTER SPLITTING OF
INITIAL TROUGH ENERGY. THE CMC HAS BEEN A WESTERN EXTREME WITH
THIS FEATURE. THE NORTHERN PORTION OF THE ORIGINAL SHORTWAVE
SHOULD BRING A SYSTEM INTO SOUTH-CENTRAL CANADA/NORTHERN TIER U.S.
AROUND MIDWEEK WITH TYPICAL SPREAD FOR SPECIFICS.
THE UPDATED FORECAST MAINTAINED THE APPROACH OF STARTING WITH AN
OPERATIONAL MODEL COMPOSITE FOR ABOUT THE FIRST HALF OF THE PERIOD
AND TRANSITIONING TO A MODEL/MEAN BLEND THEREAFTER. THIS
REFLECTED A LEAN AWAY FROM GFS SPECIFICS WHERE THE MODEL AGREED
THE LEAST WITH CONSENSUS. IN TERMS OF QPF, AMOUNTS WERE AGAIN
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 HEAVIEST RAINFALL DURING THE PERIOD WILL LIKELY EXTEND FROM
ARIZONA/NEW MEXICO INTO SOUTHERN TEXAS, WITH THE UPPER LOW
TRACKING INTO THE REGION FROM THE PACIFIC ADVECTING COPIOUS
MOISTURE OUT TO ITS EAST. INTERACTION OF THE DEEP MOISTURE WITH A
COUPLE FRONTS PUSHING SOUTHWARD ACROSS THE SOUTHERN PLAINS MAY
SERVE TO ENHANCE AMOUNTS. THE CURRENT ISSUANCE OF THE
EXPERIMENTAL DAY 5 EXCESSIVE RAINFALL OUTLOOK MAINTAINS A SLIGHT
RISK AREA OVER SOUTHERN NEW MEXICO AND SOUTHWESTERN TEXAS, WITH
MODEST EXPANSION OF THE TEXAS PORTION TO INCORPORATE LATEST
GUIDANCE FORECASTS AND FAIRLY HIGH SOIL MOISTURE. NOTE THAT THERE
IS STILL SOME SPREAD FOR THE EXACT AXIS OF HEAVIEST RAINFALL, DUE
IN PART TO DIFFERENCES IN TIMING OF THE UPPER LOW AND WHEN IT
WEAKENS.
ELSEWHERE, THE LEADING FRONT PUSHING THROUGH THE CENTRAL/EASTERN
U.S. DURING THE WEEKEND MAY SUPPORT SOME LOCALLY MODERATE TO HEAVY
RAIN FROM THE SOUTH-CENTRAL PLAINS INTO PARTS OF THE
OHIO/TENNESSEE VALLEYS, WITH THE FRONT POSSIBLY BEGINNING TO TAP
SOME OF THE MOISTURE EMERGING FROM THE SOUTHWEST. EASTERN
PORTIONS OF THIS REGION SHOULD SEE SOME RAIN IN THE SHORT TERM BUT
OVERALL DRY GROUND CONDITIONS SHOULD MITIGATE EFFECTS FROM ANY
HEAVIER BANDS OF RAIN. THIS AREA COULD STILL MERIT MONITORING,
DEPENDING ON HOW SHORTER TERM MODELS CLUSTER FOR SUCH BANDS.
PERIODS OF LAKE ENHANCED RAIN AND SNOW SHOWERS ARE LIKELY ACROSS
THE GREAT LAKES, POSSIBLY BECOMING MORE WIDESPREAD SUNDAY INTO
NEXT WEEK WITH ANOTHER FRONTAL SYSTEM AND TRAILING COLD CYCLONIC
LOW LEVEL FLOW. THE PROPORTION OF SNOW RELATIVE TO RAIN WILL
LIKELY INCREASE SOMEWHAT WITH TIME AS COLDER AIR REACHES THE EAST.
CONTINUED SPREAD FOR TIMING/EVOLUTION OF POTENTIAL LOW PRESSURE
OVER NEW ENGLAND/SOUTHEASTERN CANADA NEXT WEEK TEMPERS CONFIDENCE
IN PRECIPITATION DETAILS OVER THAT AREA.
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 10-20 DEGREES ABOVE NORMAL, MAKING IT
FEEL MORE LIKE EARLY SEPTEMBER FOR MANY AREAS. THE BEST CHANCE
FOR A FEW SCATTERED DAILY RECORD HIGHS WILL BE OVER THE PACIFIC
NORTHWEST DURING THE WEEKEND. TO THE CONTRARY, A SERIES OF FRONTS
PIVOTING AROUND THE MAIN EASTERN UPPER TROUGH/CLOSED LOW WILL
BRING PROGRESSIVELY COLDER TEMPERATURES TO AREAS EAST OF THE
ROCKIES. COOLEST ANOMALIES DURING THE WEEKEND SHOULD BE OVER THE
UPPER MIDWEST AND GREAT LAKES WITH HIGHS UP TO 10-15F BELOW
NORMAL. A MORE IMPRESSIVE SOUTHWARD/EASTWARD SURGE OF COLDER AIR
WILL SPREAD A BROAD AREA OF TEMPERATURES 10-20F OR SO BELOW NORMAL
ACROSS THE EASTERN HALF OF THE COUNTRY MONDAY-WEDNESDAY. THE
SOUTHERN PLAINS AND VICINITY WILL BE WARM THROUGH SATURDAY BUT
THEN THIS REGION WILL TREND COOLER AS RAINFALL SPREADS ACROSS THE
REGION AND DROPS HIGHS TO 10-20F BELOW NORMAL FOR MULTIPLE DAYS.
RAUSCH/HAMRICK
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN ROCKIES, THE SOUTHERN
PLAINS, AND THE SOUTHWEST, SUN-MON, OCT 16-OCT 17.
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN PLAINS, SUN-TUE, OCT
16-OCT 18.
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL
PLAINS, THE LOWER MISSISSIPPI VALLEY, THE CENTRAL APPALACHIANS,
THE TENNESSEE VALLEY, THE GREAT LAKES, THE MIDDLE MISSISSIPPI
VALLEY, THE SOUTHERN APPALACHIANS, THE UPPER MISSISSIPPI VALLEY,
THE SOUTHERN PLAINS, AND THE OHIO VALLEY, MON-WED, OCT 17-OCT 19.
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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