988
FXUS02 KWBC 131900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EDT THU OCT 13 2022
VALID 12Z SUN OCT 16 2022 - 12Z THU OCT 20 2022
..PATTERN OVERVIEW
GUIDANCE CONTINUES TO SHOW A PERSISTENT AMPLIFIED PATTERN, WITH
EASTERN U.S. TROUGHING 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 SOUTHERN ROCKIES/HIGH PLAINS, ALONG WITH VERY
WARM TEMPERATURES OVER THE NORTHWEST. THE SOUTHWEST UPPER LOW
SHOULD PRODUCE HEAVY RAINFALL FROM PARTS OF THE SOUTHWEST TO THE
TEXAS GULF COAST INTO EARLY NEXT WEEK. THE GREAT LAKES WILL SEE
MULTIPLE DAYS OF LAKE EFFECT PRECIPITATION (INCLUDING SOME SNOW)
WHILE A DEVELOPING SYSTEM EARLY IN THE WEEK MAY BRING MEANINGFUL
PRECIPITATION TO THE NORTHEAST.
..MODEL AND PREDICTABILITY ASSESSMENT
WITHIN THE EASTERN U.S. MEAN TROUGH, THE MAIN EVOLUTION OF
INTEREST INVOLVES DIGGING CENTRAL CANADA ENERGY THAT SHOULD FORM
AN UPPER LOW OVER OR NEAR THE GREAT LAKES BY EARLY NEXT WEEK. THEN
CONSENSUS TRACKS THIS UPPER LOW EASTWARD AND THEN NORTHWARD, WITH
DEVELOPING/CONSOLIDATING LOW PRESSURE LIKEWISE LIFTING NORTHWARD
WITH TIME. RECENT SLOWER TRENDS IN THE GFS THROUGH THE 12Z RUN
HAVE LED TO IMPROVED CLUSTERING FOR LOW PRESSURE/FRONTAL
PROGRESSION OVER THE NORTHEAST. IN FACT THE 12Z UKMET/CMC ARE EVEN
A LITTLE FASTER THAN THE 12Z GFS WITH THE NORTHEAST FRONT.
MODELS/ENSEMBLES STILL DEPICT THE SPLITTING OF EASTERN PACIFIC
TROUGH ENERGY EARLY NEXT WEEK. THERE IS GENERALLY TYPICAL SCATTER
FOR WHETHER THE SOUTHERN STREAM CLOSED LOW ENDS UP OFFSHORE
CALIFORNIA. HOWEVER PREDICTABILITY APPEARS LOWER FOR THE NORTHERN
ENERGY THAT ULTIMATELY ROUNDS THE WESTERN RIDGE AND DROPS INTO
SOUTHERN CANADA AND NORTHERN CONUS. THUS THERE HAS BEEN A FAIR
AMOUNT OF VARIABILITY FOR THE ASSOCIATED FRONTAL SYSTEM AND
ANCHORING WAVE. SOME OF THE SPREAD/CONTINUITY DIFFERENCES
CORRESPOND TO RECENT STRONGER TRENDS FOR THE NORTHWEST RIDGE. THIS
LATTER TREND ALSO AFFECTS IF/WHEN AN UPSTREAM FRONT MAY REACH
WESTERN CANADA (AND POSSIBLY FAR NORTHWEST U.S.) AFTER MIDWEEK.
AGREEMENT IS STEADILY IMPROVING FOR THE TIMING AND WEAKENING
PROCESS OF THE UPPER LOW CROSSING THE SOUTHWEST EARLY IN THE
PERIOD. FOR ASSOCIATED QPF THERE IS REASONABLE
AGREEMENT/CONTINUITY ACROSS THE SOUTHERN ROCKIES-HIGH PLAINS BUT
THERE HAS BEEN A NOTICEABLE TREND FOR GREATER SUPPRESSION OF THE
EASTERN TEXAS/CENTRAL GULF COAST PORTION OF THE RAINFALL SHIELD.
THE ARRAY OF LATEST GUIDANCE RECOMMENDED STARTING THE UPDATED
FORECAST WITH A 00Z/06Z MODEL COMPOSITE FOR THE FIRST HALF OF THE
PERIOD, FOLLOWED BY A TRANSITION TO A MODEL/MEAN MIX AS DETAIL
UNCERTAINTIES INCREASE. 13Z NBM QPF APPEARED REASONABLE OVER MANY
AREAS, THOUGH IT SEEMED SOMEWHAT ON THE LIGHT SIDE ALONG THE FRONT
DROPPING THROUGH THE SOUTH AND FLORIDA PENINSULA, AND BY LATE IN
THE PERIOD WITH LAKE EFFECT ACTIVITY.
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
HEAVY RAINFALL IS LIKELY TO DEVELOP OVER THE SOUTHWEST AND
SOUTHERN HIGH PLAINS SUNDAY AND THEN FOCUS OVER SOUTHERN/COASTAL
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. THE MOST CONFIDENT AREA FOR SIGNIFICANT
RAINFALL EXTENDS FROM FAR EASTERN ARIZONA TO NEAR THE BIG BEND OF
TEXAS ON SUNDAY WITH A SLIGHT RISK AREA DEPICTED IN THE
EXPERIMENTAL DAY 4 EXCESSIVE RAINFALL OUTLOOK. CONFIDENCE IS LOWER
IN THE LOCATION OF HIGHEST RAINFALL TOTALS FARTHER EAST ON MONDAY
AND SOIL CONDITIONS BECOME DRIER AS ONE MOVES EAST AS WELL, SO
ADDITIONAL TIME WILL BE NEEDED TO ASSESS ANY FLASH FLOOD THREATS
TO THE EAST OF THE SOUTHERN HIGH PLAINS. THE CLOUDS AND RAINFALL
WILL KEEP HIGH TEMPERATURES 10-20F BELOW NORMAL.
WITHIN THE LONG-TERM 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. WELL BELOW AVERAGE
TEMPERATURES (MINUS 10-20F ANOMALIES, LOCALLY GREATER FOR TUESDAY
HIGHS IN THE CENTRAL APPALACHIANS) WILL SPREAD THROUGH THE EASTERN
HALF OF THE COUNTRY BEHIND THIS SYSTEM, WITH AREAS OF LAKE EFFECT
RAIN/SNOW GRADUALLY DECREASING 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 WILL
BE POSSIBLE.
RAUSCH/KEBEDE
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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