704
FXUS02 KWBC 140700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT FRI OCT 14 2022
VALID 12Z MON OCT 17 2022 - 12Z FRI OCT 21 2022
..OVERVIEW
THE MEDIUM RANGE PERIOD WILL CONTINUE TO BE CHARACTERIZED BY
PERSISTENT AMPLIFIED/BLOCKY UPPER LEVEL FLOW, CONSISTING OF
TROUGHING IN THE EASTERN U.S. HELD IN PLACE BY STRONG RIDGES OVER
THE NORTHWEST U.S./WESTERN CANADA AND THE ATLANTIC. THE NORTHWEST
RIDGE WILL BE PART OF A LONG-TERM REX BLOCK CONFIGURATION, WITH AN
INITIAL UPPER LOW CROSSING THE SOUTHWEST AND THEN ENERGY WITHIN
THE SOUTHERN PART OF A SPLITTING EASTERN PACIFIC TROUGH FORMING A
NEW UPPER LOW OFFSHORE CALIFORNIA BY MIDWEEK. THIS PATTERN WILL
SUPPORT WELL BELOW NORMAL TEMPERATURES OVER THE EASTERN HALF OF
THE COUNTRY AS WELL AS THE SOUTHERN ROCKIES/HIGH PLAINS, ALONG
WITH VERY WARM TEMPERATURES OVER THE NORTHWEST. THE FIRST UPPER
LOW OVER THE SOUTHWEST SHOULD HELP PRODUCE NOTABLE RAINFALL FOR
PORTIONS OF NEW MEXICO AND TEXAS MONDAY AND PERHAPS LINGERING IN
SOUTHERN TEXAS TUESDAY. MEANWHILE THE ENERGY ALOFT AND WESTERLY
FLOW OVER THE GREAT LAKES WILL LEAD TO MULTIPLE DAYS OF LAKE
EFFECT PRECIPITATION (INCLUDING SOME SNOW) WHILE A DEVELOPING LOW
PRESSURE SYSTEM MAY BRING MEANINGFUL PRECIPITATION TO THE
NORTHEAST MONDAY-TUESDAY.
..MODEL AND PREDICTABILITY ASSESSMENT
MODEL CONSENSUS AT THE START OF THE MEDIUM RANGE PERIOD MONDAY/DAY
3 REMAINS QUITE GOOD FOR TROUGHING ACROSS THE EASTERN HALF OF THE
COUNTRY AND RIDGING IN MUCH OF THE WEST, WITH THE EXCEPTION OF
LINGERING ENERGY IN THE SOUTHWEST. MODELS INDICATE CANADIAN ENERGY
DIGGING SOUTHWARD INTO THE GREAT LAKES SHOULD CLOSE OFF AN UPPER
LOW WITHIN THE EASTERN TROUGH AT SOME POINT MONDAY, AND THE CLOSED
LOW SHOULD LAST THROUGH AT LEAST THURSDAY AS IT SLOWLY DRIFTS
NORTHEASTWARD. SOMEWHAT MORE QUESTIONABLE IS THE PLACEMENT OF
SURFACE LOWS AND THEIR ASSOCIATED FRONTS (AND THUS AREAS OF
ORGANIZED PRECIPITATION) THAT WILL DEPEND ON EXACT AXES OF THE
ENERGY AT ANY GIVEN TIME. BUT WITH THE LAST FEW RUNS OF THE GFS
TRENDING SLOWER TO EJECT THE UPPER LOW, GUIDANCE WAS IN GOOD
ENOUGH AGREEMENT FOR A MULTI-MODEL DETERMINISTIC BLEND. BY
WEDNESDAY-THURSDAY PREFERRED THE 18Z GFS OVER THE 12Z AS THE 00Z
UPPER LOW CENTER REMAINED FARTHER SOUTH OF CONSENSUS AND THE
ENSEMBLE MEANS. BY DAY 7/FRIDAY THERE IS MUCH MORE UNCERTAINTY
DEPENDING ON HOW UPSTREAM ENERGY ENTERS TO EVOLVE THE TROUGH.
MODELS AGREE THAT INITIAL ENERGY IN THE SOUTHWEST SHOULD WEAKEN
MONDAY-WEDNESDAY AS IT TRACKS EASTWARD, WITH REASONABLE AGREEMENT
IN THE QPF AS WELL. THEN SOME PACIFIC ENERGY IS LIKELY TO SPLIT
OFF INTO A SOUTHERN STREAM LOW OFFSHORE CALIFORNIA WITH SOME
SPREAD IN ITS POSITION. IN TERMS OF THE 12/18Z MODEL CYCLE, THE
GFS RUNS AND THE CMC WERE FAIRLY WELL CLUSTERED WITH THIS UPPER
LOW, WHILE THE UKMET WAS ON THE FASTER SIDE WITH THE ECMWF SLOWER.
THE INCOMING 00Z GUIDANCE SHOWS BETTER CLUSTERING AS THE EC WAS
FARTHER EAST SLIGHTLY WHILE BY AROUND DAY 6/THURSDAY THE GFS/CMC
REMAINED FARTHER WEST, SO HOPEFULLY THE POSITION AND THE EVENTUAL
POSSIBLE SHIFT INTO THE SOUTHWEST AND THE ASSOCIATED POTENTIAL FOR
QPF MAY BECOME MORE AGREEABLE. MEANWHILE, PREDICTABILITY REMAINS
QUITE LOW FOR THE NORTHERN ENERGY THAT ULTIMATELY ROUNDS THE
WESTERN RIDGE AND DROPS INTO SOUTHERN CANADA AND NORTHERN CONUS
WEDNESDAY-FRIDAY. ECMWF RUNS HAVE BEEN PERSISTENT IN SUPPRESSING
THE WESTERN NORTH AMERICA RIDGE SOMEWHAT, ESPECIALLY UP IN CANADA,
WITH THIS ENERGY, WHILE GFS RUNS HAVE WAVERED SOMEWHAT AND THE 12Z
STAYED PARTICULARLY RIDGY. THE ENSEMBLE MEMBERS OF EACH MODEL
SUITE FOLLOWED THEIR DETERMINISTIC MODELS FOR THE MOST PART, SO
THERE IS STILL SOME CONSIDERABLE UNCERTAINTY WITH THE UPPER FLOW
AS WELL AS FRONTAL PLACEMENT AT THE SURFACE.
THE WPC FORECAST THUS WAS BASED ON A BLEND OF DETERMINISTIC 12/18Z
GUIDANCE FOR THE EARLY PART OF THE PERIOD WITH INCREASING AMOUNTS
OF THE GEFS AND EC ENSEMBLE MEANS TO ABOUT HALF BY DAYS 6-7 AS
DETAIL UNCERTAINTIES INCREASE.
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
HEAVY RAINFALL IS LIKELY TO REMAIN ACROSS NEW MEXICO AND MUCH OF
TEXAS ON MONDAY, AIDED BY A POTENT BUT GRADUALLY WEAKENING CLOSED
LOW CROSSING THE SOUTHWEST AND A SURFACE FRONT PUSHING THROUGH THE
SOUTHERN ROCKIES/PLAINS. ISOLATED FLASH FLOODS ARE POSSIBLE WITH
THE HIGHEST RAINFALL AMOUNTS IN SOUTHERN TEXAS, BUT THE DRIER SOIL
MOISTURE MAY PRECLUDE WIDESPREAD ISSUES, PLUS THE PLACEMENT OF THE
HIGHEST QPF VARYING IN GUIDANCE LED TO NOT ENOUGH CONFIDENCE FOR
ANY SLIGHT RISK AREA IN THE DAY 4 EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK. THE INITIAL CLOUDS AND RAIN AND THE COOLER AIRMASS BEHIND
THE FRONT WILL KEEP HIGH TEMPERATURES 10-20F BELOW NORMAL THROUGH
THE FIRST HALF OF THE WEEK FOR THE SOUTHERN ROCKIES/SOUTHERN
PLAINS, GRADUALLY WARMING TO NEAR NORMAL.
WITHIN THE PERSISTENT EASTERN UPPER TROUGH, CANADIAN ENERGY
DIGGING INTO A GREAT LAKES UPPER LOW WILL DEVELOP A POTENT SURFACE
WAVE AND FRONTAL SYSTEM THAT COULD PRODUCE AREAS OF MODERATE TO
HEAVY RAINFALL OVER THE GREAT LAKES AND NORTHEAST ON MONDAY AND
TUESDAY. IMPORTANT TIMING DIFFERENCES IN THE GUIDANCE ARE BECOMING
LESS PRONOUNCED BUT ARE STILL ENOUGH TO MAINTAIN SOME UNCERTAINTY
IN COVERAGE/AMOUNTS OF ENHANCED RAIN. TUESDAY THERE MAY ACTUALLY
BE SLIGHTLY MORE CONFIDENCE COMPARED TO MONDAY WITH THE PLACEMENT
OF THE RAINFALL AXIS ACROSS MAINE WITH CONSIDERABLE MOISTURE
TRANSPORT AHEAD OF THE COLD FRONT. WELL BELOW AVERAGE TEMPERATURES
(MINUS 10-20F ANOMALIES, LOCALLY GREATER FOR TUESDAY HIGHS IN THE
CENTRAL APPALACHIANS) ARE FORECAST TO SPREAD THROUGH THE EASTERN
HALF OF THE COUNTRY BEHIND THIS SYSTEM, AND RECORDS FOR LOW
MAXIMUM TEMPERATURES MAY BE MOST COMMON, THOUGH A HANDFUL OF
RECORD LOW MINIMUM TEMPERATURES MAY BE SET AS WELL. AREAS OF LAKE
EFFECT RAIN/SNOW WILL BE WIDESPREAD MONDAY-TUESDAY BUT SHOULD
GRADUALLY DECREASE IN COVERAGE/INTENSITY AFTER MIDWEEK. HIGH
PRESSURE BUILDING OVER THE MIDWEST AND INTO THE SOUTHEAST IN THE
WAKE OF A COLD FRONT WILL SUPPORT A BROAD AREA OF DRY WEATHER.
THE PERSISTENT NORTHWEST UPPER RIDGE WILL KEEP THE REGION'S
TEMPERATURES WELL ABOVE NORMAL THROUGH THE PERIOD, WITH EACH DAY
FEATURING SOME PLUS 10-20F ANOMALIES. SCATTERED RECORD HIGHS ARE
POSSIBLE. THE WEST IS ALSO FORECAST TO REMAIN MAINLY DRY THROUGH
THE PERIOD UNTIL SOME SHOWERS MAY REACH CALIFORNIA INTO ARIZONA
LATER IN THE WEEK.
TATE/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, 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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