672
FXUS02 KWBC 150627
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 AM EDT FRI SEP 15 2023
VALID 12Z MON SEP 18 2023 - 12Z FRI SEP 22 2023
..OVERVIEW
UPPER TROUGHING AND A SURFACE COLD FRONT WILL SLIDE THROUGH THE
EAST EARLY NEXT WEEK, WITH SOME WRAP AROUND RAINS POSSIBLE ACROSS
NEW ENGLAND. THE ASSOCIATED FRONT WILL LINGER ACROSS FLORIDA
THROUGH MUCH OF THE WEEK PROVIDING A FOCUS FOR DAILY SHOWERS AND
STORMS. IN THE WEST, GUIDANCE CONTINUES TO ADVERTISE A SIGNIFICANT
PATTERN SHIFT AFTER INITIAL RIDGING WEAKENS AND MOVES EAST, WITH
AN AMPLIFYING TROUGH/POSSIBLE CLOSED LOW BRINGING WET WEATHER
ACROSS THE NORTHWEST/ROCKIES LATE IN THE WEEK. THIS SHOULD BRING A
PRONOUNCED COOLING TREND TO MOST OF THE WEST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
ON THE LARGE SCALE, THE GUIDANCE SHOW FAIRLY GOOD AGREEMENT ON
THIS OVERALL PATTERN. SOME MINOR DIFFERENCES IN THE DETAILS, BUT
WAS ABLE TO UTILIZE A TOTAL DETERMINISTIC MODEL BLEND FOR DAYS
3-5. AFTER THIS, THERE ARE SOME LARGER DIFFERENCES THAT ARISE OUT
WEST WITH THE ARRIVING TROUGH. THERE'S CONSIDERABLE RUN TO RUN
CONTINUITY AMONGST THE GFS, ECMWF, AND CMC REGARDING DEPTH AND
TIMING OF THIS TROUGH/CLOSED LOW AND SO IT SEEMED PRUDENT TO TREND
TOWARDS THE BETTER AGREEABLE ECENS AND GEFS MEANS FOR THE DAYS 6
AND 7 BLEND. THE RESULTING WPC FORECAST IS SLIGHTLY DEEPER THAN
PREVIOUS SHIFT CONTINUITY OUT WEST, BUT THAT SEEMS TO BE THE
LATEST TREND IN THE GUIDANCE.
..WEATHER/HAZARDS HIGHLIGHTS
A FRONTAL BOUNDARY STALLING OVER THE FLORIDA PENINSULA WILL
MAINTAIN A FAIRLY WET PATTERN MUCH OF THE WEEK. HOWEVER, MOISTURE
ANOMALIES ARE ONLY MODERATELY ABOVE NORMAL, FLASH FLOOD GUIDANCE
VALUES ARE HIGH, AND MODELS DO NOT SHOW MUCH CLUSTERING FOR ANY
RELATIVELY HEAVIER RAIN THAT MAY FALL. SHORTER TERM GUIDANCE MAY
ULTIMATELY HELP TO REFINE ANY AREAS THAT COULD AT LEAST MERIT A
MARGINAL RISK. WRAP AROUND PRECIPITATION ON THE BACKSIDE OF A
SURFACE LOW EXITING MAINE MAY PRODUCE SOME MODERATE RAINFALL ON
MONDAY, AND GIVEN ALREADY WET SOILS UP IN THAT REGION, IT WOULDN'T
TAKE MUCH TO CREATE AT LEAST LOCALIZED FLOODING CONCERNS. STILL,
THERE'S ENOUGH UNCERTAINTY TO PRECLUDE EVEN A MARGINAL RISK FOR
THE DAY 4/MONDAY ERO.
UPPER TROUGHING EXPECTED TO AMPLIFY OVER THE WEST NEXT WEEK SHOULD
BRING SOME PRECIPITATION TO THE PACIFIC NORTHWEST/NORTHERN ROCKIES
AND EVENTUALLY THE PLAINS. HIGH ELEVATIONS IN THE NORTHERN ROCKIES
COULD SEE SOME SNOW IF THE UPPER TROUGH AND POSSIBLE EMBEDDED LOW
ARE DEEP ENOUGH. AHEAD OF THE WESTERN TROUGH/LOW, AREAS OF RAIN
WILL LIKELY DEVELOP ACROSS THE SOUTH-CENTRAL PLAINS
TUESDAY-THURSDAY. WITH A PROLONGED FETCH FROM THE WESTERN GULF
DURING THIS TIME, HEAVY RAINFALL MAY BECOME ORGANIZED,
PARTICULARLY AROUND MID-WEEK.
AN AREA OF HIGH TEMPERATURES UP TO 15F ABOVE NORMAL SHIFTS FROM
THE NORTHERN PLAINS ON MONDAY, REACHING THE GREAT LAKES BY
THURSDAY. THE UPPER TROUGH FORECAST TO AMPLIFY OVER THE WEST NEXT
WEEK SHOULD PROMOTE A COOLING TREND OVER THE REGION STARTING
TUESDAY, WITH HIGH TEMPS 5-15F BELOW NORMAL STRETCHING FROM MT TO
SOUTHERN CA BY NEXT THURSDAY AND FRIDAY. OTHERWISE EXPECT MOST
TEMPERATURE ANOMALIES FROM THE SOUTH TO THE EAST TO BE CLOSER TO
OR A FEW DEGREES ON EITHER SIDE OF NORMAL THROUGH MUCH OF THE WEEK.
SANTORELLI
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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