489
FXUS02 KWBC 021834
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
233 PM EDT SUN OCT 02 2022
VALID 12Z WED OCT 05 2022 - 12Z SUN OCT 09 2022
..OVERVIEW
A WAVY PATTERN SHOULD BE IN PLACE BY THE START OF THE MEDIUM RANGE
PERIOD ON WEDNESDAY, WITH A COMPACT UPPER LOW SHIFTING OFF THE
MID-ATLANTIC COAST AND A SHORTWAVE MOVING INTO THE UPPER MIDWEST.
BY THURSDAY-FRIDAY, ENERGY DIVING SOUTHWARD ACROSS CANADA
COMBINING WITH THE LATTER SHORTWAVE WILL ACT TO AMPLIFY UPPER
TROUGHING ACROSS THE EAST WHILE RIDGING BUILDS OVER THE WEST, WITH
THIS PATTERN REMAINING GENERALLY STAGNANT INTO NEXT WEEKEND.
RELATIVELY QUIET WEATHER CONDITIONS ARE EXPECTED ACROSS THE CONUS
BESIDES SOME MONSOONAL MOISTURE AND WEAK ENERGY OVER THE SOUTHWEST
LEADING TO SHOWERS AND STORMS THERE, POSSIBLE LIGHT RAIN OVER
PORTIONS OF THE PLAINS, AND A POTENT COLD FRONT PUSHING ACROSS THE
CENTRAL AND EASTERN U.S. LEADING TO RAIN PARTICULARLY IN THE GREAT
LAKES REGION ALONG WITH CONSIDERABLY COOLER TEMPERATURES BEHIND
THE FRONT.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
WITH THE PATTERN BECOMING DOMINATED BY THE GENERAL RIDGE IN THE
WEST AND TROUGHING IN THE EAST, MODEL GUIDANCE REMAINS AGREEABLE
WITH THE AMPLIFIED SYNOPTIC PATTERN, BUT SMALLER SCALE DETAILS ARE
MORE UNCERTAIN. THE SURFACE LOW OFFSHORE OF THE MID-ATLANTIC IN
THE SHORT RANGE PERIOD AND INTO DAY 3/WEDNESDAY HAS BEEN WAFFLING
IN ITS PLACEMENT, NAMELY HOW CLOSE IT IS TO THE COAST AND THUS HOW
MUCH QPF REMAINS ONSHORE. THE 00Z/06Z MODEL GUIDANCE ON THE WHOLE
PULLED THE LOW CLOSER TO SHORE AND THE WPC FORECAST TRENDED IN
THIS DIRECTION. AFTER THAT, SHORTWAVES MOVING THROUGH THE EASTERN
TROUGH SHOW FAIRLY GOOD AGREEMENT THROUGH AROUND FRIDAY BUT MORE
DIFFERENCES ARISE INTO NEXT WEEKEND AS SHORTWAVES TAKE DIFFERENT
TRACKS AND EVOLVE THE PATTERN. GFS RUNS INDICATED ONE DEEPER
TROUGH THROUGH SUNDAY, WHILE THE 00Z ECMWF AND CMC HAD SOME
SHORTWAVES WITHIN THE TROUGH WITH LESS OVERALL AMPLIFICATION. WITH
MODEL INCONSISTENCIES FROM RUN TO RUN IT IS DIFFICULT TO FAVOR ONE
SOLUTION OVER ANOTHER. THE 00Z GFS MAINTAINED MORE RIDGE/TROUGH
AMPLIFICATION THROUGH SUNDAY THAN BASICALLY ANY ENSEMBLE MEMBER
THOUGH. THE WPC FORECAST WAS BASED ON A MULTI-MODEL DETERMINISTIC
BLEND EARLY BUT WITH INCREASING PROPORTIONS OF THE EC AND GEFS
ENSEMBLE MEANS IN THE FRONTS/PRESSURES BLEND AS THE PERIOD
PROGRESSED TO SMOOTH OUT INDIVIDUAL MODEL DIFFERENCES. THIS ALSO
WORKED WELL OUT WEST WHERE INDIVIDUAL ENSEMBLE MEMBERS SHOW QUITE
A BIT OF SPREAD REGARDING ENERGY ROUNDING THE TOP OF THE RIDGE
INTO THE ROCKIES AND HOW MUCH INFLUENCE THIS MIGHT HAVE ON RIDGE
BREAKDOWN. THE QPF WAS BASED LARGELY ON THE 13Z NATIONAL BLEND OF
MODELS, BUT WITH A WIDER FOOTPRINT FOR LIGHT AMOUNTS ADDED ACROSS
MUCH OF THE COUNTRY AS THIS UNDERFORECAST OF LOW AMOUNTS FROM THE
NBM IS A KNOWN BIAS.
..WEATHER/HAZARDS HIGHLIGHTS
THOUGH A SURFACE LOW HAS WAFFLED A BIT IN ITS PLACEMENT AND
TRENDED BACK TOWARD THE MID-ATLANTIC COAST OVERALL AT THE START OF
THE MEDIUM RANGE PERIOD WEDNESDAY MORNING, GUSTY WINDS AND
RAINFALL FOR COASTAL LOCATIONS OF THE MID-ATLANTIC AND NORTHEAST
SHOULD END ON WEDNESDAY AS IT TRACKS FARTHER INTO THE ATLANTIC.
MEANWHILE, MONSOONAL MOISTURE INTO THE SOUTHWEST WILL CONTINUE TO
DRIVE SOME DIURNAL SHOWERS AND THUNDERSTORMS, WITH LOCALLY HEAVY
RAINFALL POSSIBLE. RAINFALL INTENSITY MAY WANE AFTER WEDNESDAY,
BUT SHOWERS COULD LINGER THROUGH THE WEEKEND ACROSS THE FOUR
CORNERS STATES. TO THE NORTH, A COLD FRONT SHIFTING FROM THE
NORTHERN PLAINS TO THE UPPER MIDWEST AND GREAT LAKES SHOULD RESULT
IN RAIN AS THE FRONT MOVES THROUGH AROUND THURSDAY, AND LAKE
ENHANCED SHOWERS IN THE WESTERLY FLOW BEHIND THE FRONT FRIDAY AND
PERHAPS SATURDAY.
TEMPERATURES OUT WEST WILL BE WARM THROUGH THE WEEK INTO NEXT
WEEKEND UNDERNEATH A BLOCKY UPPER RIDGE, WITH DAYTIME HIGHS OVER
THE NORTHWEST 10 TO 15 DEGREES ABOVE NORMAL. DESPITE THE
ANOMALIES, THE RESULTING TEMPERATURES PEAKING IN THE 70S AND 80S
(90S FOR PARTS OF CALIFORNIA) ARE UNLIKELY TO CREATE ANY HEAT
RELATED HAZARDS. CONVERSELY, CANADIAN HIGH PRESSURE SPILLING INTO
THE NORTH-CENTRAL U.S. AND EXPANDING EASTWARD BEHIND THE COLD
FRONT WILL RESULT IN MUCH BELOW NORMAL TEMPERATURES SHIFTING FROM
THE NORTHERN PLAINS INTO THE MIDWEST AND INTO MUCH OF THE EAST
THURSDAY-SUNDAY. DAYTIME HIGHS IN SOME LOCATIONS COULD BE 15 TO 20
DEGREES BELOW AVERAGE WHILE OVERNIGHT TEMPERATURES ARE FORECAST TO
DROP INTO THE 30S FOR MANY, AND EVEN 20S FOR NORTH DAKOTA AND
NORTHERN MINNESOTA PARTICULARLY FRIDAY MORNING.
TATE/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, 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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