008
FXUS02 KWBC 142037
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
436 PM EDT FRI OCT 14 2022
VALID 12Z MON OCT 17 2022 - 12Z FRI OCT 21 2022
..OVERVIEW
GUIDANCE CONTINUES TO SHOW AMPLIFIED/BLOCKY UPPER LEVEL FLOW FOR
MOST OF THE PERIOD, WITH 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 REX BLOCK
CONFIGURATION, WITH A SHORT-TERM UPPER LOW WEAKENING OVER THE
SOUTHERN ROCKIES ON MONDAY AND ANOTHER UPPER LOW FORMING OFFSHORE
CALIFORNIA BY MIDWEEK AS UPSTREAM EASTERN PACIFIC TROUGH ENERGY
SPLITS. AROUND THE END OF NEXT WEEK THE MODELS/MEANS SUGGEST THE
START OF A TRANSITION TO A NEW PATTERN, WITH DIFFERENCES IN HOW
THIS WILL OCCUR. THE ESTABLISHED PATTERN FOR MOST OF THE PERIOD
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 WEAKENING
SOUTHERN ROCKIES UPPER LOW 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 AND LEADING WAVY FRONT MAY BRING MEANINGFUL
PRECIPITATION TO THE NORTHEAST MONDAY-TUESDAY.
..MODEL AND PREDICTABILITY ASSESSMENT
OVERALL THE GUIDANCE HAS SETTLED INTO A REASONABLE CLUSTER FOR THE
EARLY-MID WEEK EVOLUTION OVER THE EAST, WITH AN UPPER LOW LIKELY
TRACKING EASTWARD FROM THE UPPER GREAT LAKES AND THEN LIFTING
NORTHWARD OVER WESTERN QUEBEC. ASSOCIATED LOW PRESSURE OVER
SOUTHEASTERN CANADA SHOULD ANCHOR A WAVY COLD FRONT THAT LIFTS
THROUGH THE NORTHEAST. THERE IS STILL SOME SPREAD FOR EXACT
DETAILS OF FRONTAL TIMING/WAVINESS, WHICH WILL IMPORTANT FOR
RAINFALL COVERAGE AND AMOUNTS, BUT CURRENT DIFFERENCES ARE
GENERALLY WITHIN TYPICAL GUIDANCE SPREAD AND ERROR RANGES FOR 3-5
DAYS OUT IN TIME.
FARTHER UPSTREAM THERE HAS BEEN A CONSISTENT SIGNAL FOR NORTHERN
STREAM PACIFIC ENERGY TO ROUND THE WESTERN RIDGE AND THEN DROP
INTO THE EASTERN U.S. MEAN TROUGH, SUPPORTING A FRONTAL SYSTEM
THAT PUSHES INTO THE LOWER 48 TO THE EAST OF THE ROCKIES AROUND
MID-LATE WEEK. HOWEVER THERE HAS BEEN A FAIR DEGREE OF SPREAD OVER
THE DETAILS OF THIS ENERGY AND ASSOCIATED SURFACE SYSTEM OVER
RECENT DAYS, REFLECTING THE TYPICALLY LOWER PREDICTABILITY FOR
RESOLVING SPECIFICS OF SUCH SHORTWAVES. THERE ARE STILL NOTICEABLE
DIFFERENCES IN THE NEW 12Z RUN BUT THE MODELS DO SEEM TO BE
TRENDING A LITTLE CLOSER TOGETHER.
AFTER MIDWEEK LARGER SCALE PATTERN ISSUES START TO ARISE, AS
ECMWF/ECMWF MEAN RUNS HAVE CONSISTENTLY BEEN MOST AGGRESSIVE TO
FLATTEN THE NORTHWEST U.S./WESTERN CANADA UPPER RIDGE. IN
CONTRAST, THE PAST COUPLE DAYS OF GFS/GEFS RUNS HAVE ACTUALLY
TRENDED STRONGER WITH THE RIDGE. THE CMC/CMC MEAN OFFER A
COMPROMISE THAT TILTS SOMEWHAT IN THE GFS/GEFS DIRECTION. THE 00Z
ECMWF WAS ON THE QUICK SIDE TO SPLIT ITS EAST-CENTRAL PACIFIC FLOW
AROUND MIDWEEK AND MAY BE SOMEWHAT AGGRESSIVE TO BREAK DOWN THE
RIDGE, WITH CONSENSUS PARTICULARLY EMPHATIC ABOUT MAINTAINING
BROADER CYCLONIC FLOW OVER THE EAST INTO FRIDAY VERSUS THE ECMWF.
TELECONNECTIONS RELATIVE TO THE CORE OF POSITIVE HEIGHT ANOMALIES
OVER THE PACIFIC IN THE D+8 MULTI-DAY MEANS SUPPORT EVENTUAL
TROUGHING NEAR/INLAND FROM THE WEST COAST--WHICH MOST GUIDANCE
SHOWS BY NEXT WEEKEND. THUS AN INTERMEDIATE SOLUTION CLOSE TO
CONTINUITY APPEARS BEST AT THIS TIME. FARTHER SOUTH, THE GEFS MEAN
AND CMC/CMCENS ARE FASTEST WITH THE NEXT UPPER LOW APPROACHING THE
SOUTHWEST WHILE THE ECMWF/ECMWF MEAN ARE SLOWEST. A COMPROMISE
CURRENTLY LOOKS GOOD FOR RESOLVING THIS SPREAD.
THE UPDATED FORECAST MAINTAINED THE APPROACH OF USING A 12Z/18Z
OPERATIONAL MODEL COMPOSITE FOR ABOUT THE FIRST HALF OF THE PERIOD
FOLLOWED BY A TRANSITION TO A BLEND OF MODELS AND GEFS/ECMWF MEANS
BY DAYS 6-7 THURSDAY-FRIDAY. THIS YIELDED THE DESIRED INTERMEDIATE
SOLUTION SIMILAR TO CONTINUITY WITH THE INCREASING SPREAD LATE IN
THE FORECAST.
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
HEAVY RAINFALL IS LIKELY TO REMAIN ACROSS NEW MEXICO AND MUCH OF
THE SOUTHWESTERN HALF OF TEXAS ON MONDAY, AIDED BY A WEAKENING
CLOSED LOW CROSSING THE SOUTHWEST AND A SURFACE FRONT PUSHING
THROUGH AND SOUTH OF SOUTHERN TEXAS. ISOLATED FLASH FLOODS ARE
POSSIBLE WITH THE HIGHEST RAINFALL AMOUNTS IN SOUTHERN TEXAS, BUT
THE DRIER SOIL MOISTURE MAY PRECLUDE WIDESPREAD ISSUES. ALSO THE
CONTINUED SCATTER IN GUIDANCE PLACEMENT OF THE HIGHEST QPF WITHIN
THIS GENERAL AREA KEEPS CONFIDENCE LOW ENOUGH NOT TO INTRODUCE ANY
SLIGHT RISK AREA IN THE DAY 4 EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK. THE INITIAL CLOUDS/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 BY LATE IN THE WEEK.
WITHIN THE PERSISTENT EASTERN UPPER TROUGH, CANADIAN ENERGY
DIGGING INTO A GREAT LAKES UPPER LOW BY MONDAY 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. LATEST MODELS
ARE GENERALLY SUGGESTING THAT HEAVIEST RAINFALL POTENTIAL ALONG
THE FRONT MAY BE ON TUESDAY WITH CONSIDERABLE MOISTURE TRANSPORT
AHEAD OF THE FRONT. HOWEVER IT WILL BE A VERY CLOSE CALL AS TO
WHETHER THIS BAND OF HEAVY RAIN WILL BE OVER PARTS OF MAINE OR
JUST TO THE EAST, DEPENDING ON FINE-SCALE UPPER SHORTWAVE/FRONTAL
WAVE DETAILS THAT MAY NOT BE FULLY RESOLVED UNTIL THE SHORT RANGE.
WELL BELOW AVERAGE TEMPERATURES (MINUS 10-20F ANOMALIES, LOCALLY
GREATER OVER SOME AREAS MONDAY-TUESDAY) WILL SPREAD THROUGH THE
EASTERN HALF OF THE COUNTRY BEHIND THIS SYSTEM. RECORDS FOR LOW
MAXIMUM TEMPERATURES MAY BE MOST COMMON, THOUGH A HANDFUL OF
RECORD LOW MINIMUM TEMPERATURES MAY BE SET AS WELL. THESE
TEMPERATURES WILL PROVIDE AN EARLY PREVIEW OF NOVEMBER/DECEMBER.
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 NORTHWEST UPPER RIDGE PERSISTING INTO AT LEAST THURSDAY WILL
KEEP TEMPERATURES OVER THE REGION WELL ABOVE NORMAL THROUGH THE
PERIOD, WITH EACH DAY FEATURING SOME PLUS 10-20F ANOMALIES.
SCATTERED RECORD HIGHS ARE POSSIBLE. SOME OF THIS WARMTH WILL
GRADUALLY SPREAD INTO THE NORTHERN-CENTRAL PLAINS BY
WEDNESDAY-THURSDAY. EXPECT THE WEST TO REMAIN MAINLY DRY THROUGH
THE PERIOD UNTIL SOME SHOWERS MAY REACH THE SOUTHWESTERN U.S.
LATER IN THE WEEK AS THE NEXT UPPER LOW APPROACHES. THE FAR
NORTHERN PARTS OF THE NORTHWEST COULD BEGIN TO SEE A LITTLE
PRECIPITATION BY THE END OF THE WEEK DEPENDING ON HOW QUICKLY THE
UPPER RIDGE WEAKENS.
RAUSCH/TATE
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
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE NORTHEAST AND THE SOUTHERN
PLAINS, MON-TUE, OCT 17-OCT 18.
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN ROCKIES AND THE
SOUTHERN PLAINS, MON, OCT 17.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHEAST.
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL
PLAINS, THE LOWER MISSISSIPPI
VALLEY, THE CENTRAL APPALACHIANS, THE TENNESSEE VALLEY, THE GREAT
LAKES, THE MIDDLE MISSISSIPPI
VALLEY, THE SOUTHERN APPALACHIANS, THE UPPER MISSISSIPPI VALLEY,
THE SOUTHERN PLAINS, AND THE OHIO
VALLEY, MON-WED, OCT 17-OCT 19.
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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