741
FXUS02 KWBC 141749
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 PM EDT SAT OCT 14 2023
VALID 12Z TUE OCT 17 2023 - 12Z SAT OCT 21 2023
..OVERVIEW
THE MODELS AND ENSEMBLE MEANS CONTINUE TO SHOW THE UPPER PATTERN
TRANSITIONING TO AN AMPLIFIED WESTERN RIDGE/EASTERN TROUGH
CONFIGURATION FOR THE LATTER HALF OF THE COMING WEEK, AIDED BY THE
EXTRATROPICAL REFLECTION OF BOLAVEN WHICH SHOULD REACH THE
EAST-CENTRAL PACIFIC BY THE START OF THE FORECAST PERIOD EARLY
TUESDAY. THE AMPLIFYING CENTRAL-EASTERN U.S. TROUGH AND LEADING
FRONT/LOW PRESSURE SHOULD PRODUCE SOME AREAS OF LIGHT TO MODERATE
RAINFALL, WITH SOME AREAS OF HEAVIER ACTIVITY POSSIBLE OVER THE
EAST BY THE END OF THE WEEK DEPENDING ON UNCERTAIN EXACT DETAILS
OF UPPER FLOW AND SURFACE EVOLUTION. MEANWHILE AN UPPER TROUGH
OVER THE EAST COAST ON TUESDAY SHOULD QUICKLY DEPART, AND
SHORTWAVE ENERGY BEHIND THE BUILDING WESTERN U.S. UPPER RIDGE MAY
BRING A FRONT AND ASSOCIATED MOISTURE CLOSE TO THE WEST COAST BY
NEXT SATURDAY. THE FORECAST PATTERN WILL PROMOTE ABOVE NORMAL
TEMPERATURES OVER THE WEST AND AT TIMES INTO THE HIGH PLAINS,
ALONG WITH NEAR TO BELOW NORMAL READINGS OVER THE EAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THERE ARE SOME PLACEMENT/INTENSITY DISAGREEMENTS WITH THE LEADING
TROUGH OFF THE EAST COAST ON TUESDAY, BUT THERE IS AGREEMENT THE
ASSOCIATED SURFACE LOW WILL BE WELL OFF THE COAST TO PRESENT ANY
KIND OF SENSIBLE WEATHER THREAT TO THE EAST COAST. THE BIGGER
FORECAST CHALLENGE ARE WITH THE DETAILS AS A SHORTWAVE THROUGH THE
NORTH-CENTRAL U.S. AMPLIFIES AS IT REACHES THE EAST LATE NEXT
WEEK. MODELS GENERALLY HAVE TRENDED A LITTLE MORE PROGRESSIVE WITH
THIS SYSTEM, BUT ADDITIONAL NORTHERN STREAM ENERGY DROPPING INTO
THIS SYSTEM AS IT REACHES THE EAST COAST PRESENT A LOT OF RUN TO
RUN VARIABILITY ON THE EVENTUAL EVOLUTION. 00Z/06Z DETERMINISTIC
MODEL RUNS SHOW PRETTY GOOD AGREEMENT EVEN BY DAY 7, BUT ENSEMBLE
SPREAD IS STILL QUITE LARGE WITH THIS SYSTEM, SUGGESTING A LOW
PREDICTABILITY/CONFIDENCE FORECAST. ELSEWHERE, RECENT GUIDANCE
TRENDS HAVE HELD ONTO THE IDEA OF FARTHER OFFSHORE ATLANTIC LOW
PRESSURE THROUGH MIDWEEK DUE TO THE DEPARTING EASTERN U.S. UPPER
TROUGH BEING SUFFICIENTLY OPEN, WHILE GUIDANCE SHOWS ONLY MODEST
SPREAD RELATIVE TO DAY 7 FORECASTS FOR THE SHORTWAVE/SURFACE FRONT
NEARING THE WEST COAST LATE IN THE PERIOD.THE WPC FORECAST TODAY
USED A PURELY DETERMINISTIC MODEL BLEND FOR THE EARLY PERIODS,
BRINGING IN MORE AND MORE ENSEMBLE MEANS LATE PERIOD TO ACCOUNT
FOR THE UNCERTAINTY AND TO HELP MAINTAIN SHIFT TO SHIFT CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
SOME LOCATIONS OVER AND NEAR THE NORTHERN ROCKIES MAY SEE MOSTLY
LIGHT PRECIPITATION ON TUESDAY AS A SHORTWAVE AND SURFACE SYSTEM
CROSS THE REGION. AFTER THAT TIME, UPPER TROUGH AMPLIFICATION
SHOULD SUPPORT SOMEWHAT GREATER COVERAGE OF RAINFALL SPREADING
ACROSS THE CENTRAL AND EASTERN U.S. ALONG AND AHEAD OF THE
CORRESPONDING SURFACE SYSTEM(S). CONFIDENCE IN SPECIFICS IS STILL
NOT GREAT THOUGH, GIVEN THE UNCERTAINTY IN UPPER TROUGH/SURFACE
DETAILS DURING THE LATTER HALF OF THE WEEK. CURRENTLY EXPECT
PROGRESSION TO BE SUFFICIENT FOR MOST CENTRAL U.S. RAINFALL TO BE
IN THE LIGHT TO MODERATE RANGE, WITH SOMEWHAT HEAVIER ACTIVITY
POSSIBLE OVER THE SOUTHEASTERN PLAINS/LOWER MISSISSIPPI VALLEY.
MOIST EASTERLY LOW LEVEL FLOW ACROSS FLORIDA SHOULD INCREASE
RAINFALL OVER THE STATE LATE IN THE WEEK, AND SOME OF THIS
MOISTURE COULD ULTIMATELY GET PULLED FARTHER NORTH OVER THE
EASTERN U.S. BY FRIDAY-SATURDAY. COVERAGE AND INTENSITY OF
RAINFALL OVER THE EAST WILL DEPEND ON HOW MUCH THE UPPER TROUGH
MAY DECELERATE/CLOSE OFF AT THAT TIME. ELSEWHERE, NORTHERN
PORTIONS OF THE PACIFIC NORTHWEST COULD SEE A LITTLE RAINFALL
DURING THE PERIOD WITH A SLIGHT INCREASE POSSIBLE BY THE END OF
THE WEEK AS A FRONT APPROACHES. SOME SCATTERED LIGHT RAIN MAY
LINGER INTO TUESDAY OVER THE EASTERN GREAT LAKES/APPALACHIANS INTO
THE NORTHEAST BEFORE A DRIER TREND.
EXPECT ABOVE NORMAL TEMPERATURES OVER THE WEST INTO HIGH PLAINS
AND NEAR TO BELOW NORMAL READINGS OVER THE EAST. WARMEST ANOMALIES
WILL LIKELY BE OVER THE HIGH PLAINS ON TUESDAY AND THEN WITH
INCREASING COVERAGE OVER THE NORTHERN ROCKIES INTO
NORTHERN-CENTRAL HIGH PLAINS LATE IN THE WEEK, WITH HIGHS 10-20F
ABOVE NORMAL. COOLEST ANOMALIES OVER THE EAST, INCLUDING FLORIDA,
SHOULD BE ON TUESDAY WITH SOME HIGHS AT LEAST 10F BELOW NORMAL.
AFTER SOME MODERATION WITH THE DEPARTURE OF THE TUESDAY TROUGH,
THE SOUTHERN HALF OF THE EAST SHOULD COOL DOWN ONCE AGAIN WITH THE
ARRIVAL OF THE UPSTREAM AMPLIFIED TROUGH BY THE END OF THE WEEK.
SANTORELLI/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 FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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