001
FXUS02 KWBC 281915
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 PM EDT FRI OCT 28 2022
VALID 12Z MON OCT 31 2022 - 12Z FRI NOV 04 2022
...PACIFIC NORTHWEST HEAVY RAIN LINGERING INTO MONDAY FOLLOWED BY
GREAT BASIN/ROCKIES HEAVY MOUNTAIN SNOW THREAT...
...INCREASING CHANCES OF HEAVY RAINFALL ALONG THE WESTERN GULF
COAST TUESDAY...
..OVERVIEW
FOCUS DURING THE EARLY MEDIUM-RANGE PERIOD WILL BE ON A SOUTHERN
STREAM TROUGH LIFTING NORTHEASTWARD ACROSS THE SOUTHERN PLAINS
WHICH MAY LEAD TO SOME HEAVIER, EXCESSIVE RAINFALL, ESPECIALLY
NEAR THE WESTERN GULF COAST ON TUESDAY. ANOTHER SMALL SCALE
SHORTWAVE WILL MOVE THROUGH THE MIDWEST BRINGING A CHANCE FOR
SHOWERS AND THUNDERSTORMS FROM THE OHIO VALLEY TO THE EAST COAST
MONDAY. EXPECT AN INCREASINGLY AMPLIFIED UPPER PATTERN OVER THE
LOWER 48 BY LATER IN THE WEEK, WITH A DEEP TROUGH DIGGING IN THE
WEST WHILE MEAN RIDGING BUILDS OVER THE EAST. THE UPPER TROUGH
WILL SPREAD A BROAD AREA OF RAIN AND MOUNTAIN SNOW, ALONG WITH
WELL BELOW NORMAL TEMPERATURES, ACROSS THE WEST. WITHIN A BROAD
AREA OF MOSTLY ABOVE NORMAL TEMPERATURES EAST OF THE ROCKIES, THE
WARMEST ANOMALIES SHOULD GENERALLY BE CENTERED OVER THE
NORTHERN-CENTRAL PLAINS AND UPPER MIDWEST.
..GUIDANCE AND PREDICTABILITY ASSESSMENT
MODEL GUIDANCE SHOWED BROAD GENERAL AGREEMENT EARLY IN THE PERIOD
WITH MORE SIGNIFICANT DIFFERENCES WITH RESPECT TO THE PROGRESSION
AND AMPLIFICATION OF THE WESTERN TROUGH LATER IN THE PERIOD. A
CLUSTER OF SOLUTIONS TENDED TO FOLLOW THE SAME PATTERN IN GENERAL,
LEADING TO AT LEAST AN AVERAGE LEVEL OF CONFIDENCE IN THE
FORECAST. THE MODEL BLEND USED FOR THE MEDIUM RANGE PRODUCT SUITE
BEGAN WITH A COMBINATION OF THE 00 UTC ECMWF/CMC/UKMET AND 06 UTC
GFS WHICH CLUSTERED AROUND THE SAME SOLUTION WITH CONTINUITY FROM
THE PRIOR FORECAST. THE 00 UTC CMC/UKMET QUICKLY STARTED TO
DIVERGE COMPARED TO CONTINUITY AND THE 00 UTC ECMWF AND 06 UTC GFS
WITH RESPECT TO THE SOUTHERN STREAM TROUGH LIFTING OVER THE
SOUTHERN PLAINS. BEGAN TO TREND AWAY FROM THESE SOLUTIONS IN THE
BLEND WITH THE UKMET SHOWING A BROADER TROUGH AND THE CMC A MORE
AMPLIFIED TROUGH. THIS PATTERN CONTINUED LATER IN THE PERIOD WITH
THE 00 UTC UKMET/CMC TRENDING AWAY FROM THE 00 UTC ECMWF AND 06
UTC GFS IN BOTH THE AMPLITUDE AND PHASE OF THE OVERALL PATTERN
OVER THE CONUS. THE FOCUS TURNED TO THE EVOLUTION OF THE TROUGH
DIGGING OVER THE WESTERN CONUS LATER IN THE PERIOD. THE 00 UTC
ECMWF TRENDED TOWARDS THE 06 Z GFS DEPICTING A CLOSED LOW COMPARED
TO THEIR RESPECTIVE ENSEMBLE MEANS. THERE WAS ALSO A SIGNIFICANT
DIFFERENCE IN THE 06 UTC GFS COMPARED TO THE 00 UTC GFS WHICH HAD
A MORE PROGRESSIVE AND AMPLIFIED TROUGH, BUT WAS AN OUTLIER
COMPARED TO THE OTHER SOLUTIONS. KEPT A SPLIT OF THE 06 UTC GFS
AND 00 UTC ECMWF DURING THE LATER HALF OF THE FORECAST PERIOD WITH
A SLOW RAMP UP OF THE 00 UTC ECMWF MEAN WHICH DOES NOT MAINTAIN
THE CLOSED LOW AS LONG INTO THE FORECAST. THIS FOLLOWED CONTINUITY
WITH THE PRIOR FORECAST AND ALSO ALLOWS FOR SOME UNCERTAINTY IN
THE EVOLUTION OF A DEEPER, LESS PROGRESSIVE TROUGH GIVEN THE
VARIED SOLUTIONS OF THE 00 AND 06 UTC GFS.
..WEATHER/HAZARD HIGHLIGHTS
THE UPPER TROUGH AMPLIFYING INTO THE WEST AND LEADING SURFACE
FRONTAL SYSTEM WILL BRING A PERIOD OF WETTER AND COLDER WEATHER TO
THE REGION. THE COMBINATION OF DYNAMICS AND MOISTURE SHOULD
SPREAD LOCALLY ENHANCED PRECIPITATION SOUTHEASTWARD WITH TIME,
FROM THE PACIFIC NORTHWEST/FAR NORTHERN ROCKIES INTO
CALIFORNIA/GREAT BASIN AND THEN THE SOUTHWEST U.S. AND CENTRAL
ROCKIES. PACIFIC NORTHWEST ACTIVITY ON MONDAY WILL BE A SOMEWHAT
TEMPERED CONTINUATION OF HEAVY WEEKEND PRECIPITATION OVER THE
COASTAL RANGES/OLYMPICS AND CASCADES. SOUTHEASTWARD PROGRESSION
OF THE MOISTURE SHIELD WILL BRING A THREAT FOR HEAVY MOUNTAIN SNOW
INTO NORTHERN-CENTRAL CALIFORNIA AND ACROSS THE NORTH-CENTRAL
GREAT BASIN/ROCKIES AS DEPICTED IN THE WPC WINTER WEATHER OUTLOOK
PROBABILITIES. THERE IS STILL A BIT OF UNCERTAINTY WITH RESPECT TO
FORECAST QPF AND THUS SNOW AMOUNTS. QPF FROM THE NBM TENDED TO BE
HIGHER ACROSS THE REGION WHEN COMPARED TO OTHER GUIDANCE. A
MULTI-MODEL ENSEMBLE BLEND WAS USED TO REDUCE AMOUNTS BROADLY
ACROSS THE REGION. HOWEVER, THE INDIVIDUAL TOTALS FOR VARIOUS
MOUNTAIN RANGES, ESPECIALLY FOR SOUTHERN CALIFORNIA AND THE
SOUTHWEST, STILL VARIED QUITE A BIT COMPARED TO THE PRIOR FORECAST
AND INDIVIDUAL MODEL GUIDANCE. THUS, THE DETAILS OF THE EVOLUTION
OF THE PROGRESSION OF THE TROUGH AND AMOUNT OF COLD AIR THAT
EVENTUALLY OVERSPREADS SOUTHERN PORTIONS OF THE WEST WILL NEED TO
BE CLOSELY MONITORED WITH THIS HIGHER LEVEL OF UNCERTAINTY.
TEMPERATURES ACROSS THE WEST WILL TREND MUCH COLDER AS THE UPPER
TROUGH ARRIVES AND DRIFTS OVER THE REGION. IN ADDITION TO THE
FORECAST PRECIPITATION, MUCH OF THE SOUTHERN HALF TO TWO-THIRDS OF
THE WEST WILL LIKELY SEE DAYTIME HIGHS 10-20F BELOW NORMAL BY NEXT
WEDNESDAY-FRIDAY, WHICH SUCH ANOMALIES MAY BE MORE SCATTERED OVER
NORTHERN AREAS.
RAINFALL IS EXPECTED TO INCREASE IN COVERAGE AND INTENSITY OVER
THE CENTRAL U.S. LATE NEXT WEEK AS THE WESTERN UPPER TROUGH
APPROACHES, WITH EXACT TIMING SENSITIVE TO PROGRESSION OF THE
TROUGH. THERE SHOULD BE TWO PRIMARY AREAS OF RAIN AHEAD OF THIS
SYSTEM. ONE WILL BE WITH THE SHORTWAVE/SURFACE SYSTEM EMERGING
FROM THE MIDWEST MONDAY WHICH WILL BRING AT LEAST A BROAD AREA OF
LIGHT TO MODERATE RAINFALL FROM THE OHIO VALLEY/LOWER GREAT LAKES
TO THE CAROLINAS AND MID-ATLANTIC. THE TRAILING FEATURE TO THE
SOUTH MAY PRODUCE ONE OR MORE AREAS OF HEAVY RAINFALL OVER THE
GULF COAST REGION. WHILE THERE IS SOME UNCERTAINTY IN HOW MUCH
RAIN FALLS ALONG/INLAND FROM THE GULF COAST VERSUS OFFSHORE, THE
FORECAST RAINFALL AMOUNTS HAVE TRENDED UPWARD. THE COVERAGE AND
INTENSITY OF THE QPF ACROSS THE MODEL GUIDANCE IS ENOUGH TO
HIGHLIGHT A CONCERN FOR LOCALIZED EXCESSIVE RAINFALL ON TUESDAY.
AREAS TO THE EAST OF THE ROCKIES WILL BE ON THE WARM SIDE OF THE
AMPLIFYING PATTERN FOR MOST OF NEXT WEEK, WITH TEMPERATURES OF
10-20F ABOVE NORMAL MOST COMMON OVER THE NORTHERN-CENTRAL
PLAINS/UPPER MIDWEST. SOME OF THESE WARM ANOMALIES WILL EXTEND
FARTHER EAST AT TIMES, WHILE COOLER AIR SHOULD START TO REACH THE
PLAINS BY FRIDAY.
PUTNAM/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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page