899
FXUS02 KWBC 070701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT SAT OCT 07 2023
VALID 12Z TUE OCT 10 2023 - 12Z SAT OCT 14 2023
...INCREASING HEAVY RAIN THREATS FOR THE MIDWEST AND GULF
COAST/NORTHERN FLORIDA BY MID TO LATE NEXT WEEK...
..OVERVIEW
IT REMAINS THE CASE THAT A DEEP UPPER LEVEL LOW IS FORECAST TO
PARK ITSELF OVER SOUTHEASTERN CANADA AND THE GREAT LAKES AND CHURN
IN PLACE THROUGH MOST OF NEXT WEEK. A NEARLY STATIONARY SURFACE
LOW WILL CREATE PRECIPITATION CHANCES NEAR THE GREAT LAKES EARLY
IN THE WEEK WITH SOME LAKE EFFECT ENHANCEMENT POSSIBLE. IN THE
WEST, A TROUGH WILL MOVE ONSHORE EARLY IN THE WEEK DIVING THROUGH
THE WEST WITH SOME CHANCE FOR CLOSED UPPER LOW DEVELOPMENT OVER
THE ROCKIES AROUND THURSDAY. THIS FEATURE WILL DRIVE A SURFACE
FRONTAL SYSTEM EAST ACROSS THE COUNTRY THROUGH THE WEEK.
PRECIPITATION CHANCES WILL BE GREATEST INTO TUESDAY IN THE PACIFIC
NORTHWEST WHERE LOCALLY HEAVY DOWNPOURS MAY BE POSSIBLE, THEN
PRECIPITATION WILL SPREAD INTO THE CENTRAL U.S. MIDWEEK AND TO THE
EAST COAST/NORTHEAST BY FRIDAY. A FRONTAL BOUNDARY WITH DEEPENED
TROPICAL MOISTURE LIFTING THROUGH THE GULF AND FLORIDA WILL
INCREASE PRECIPITATION CHANCES ACROSS FLORIDA/THE GULF COAST THEN
SOUTHEAST AS WELL BY MID TO LATER IN THE WEEK BEFORE LIFTING UP
THE EAST COAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL AND ENSEMBLE SOLUTIONS SEEM OVERALL REASONABLY WELL
CLUSTERED WITH THE MID-LARGER SCALE PATTERN EVOLUTION AND THE MAIN
WEATHER FOCUSING SYSTEMS NEXT WEEK, BUT THE GFS/GEFS DO OFFER
GENERALLY MORE PROGRESSIVE TIMING AND DOWNSTREAM DEVELOPMENTS. A
COMPOSITE BLEND OF THE ECMWF/CANADIAN/UKMET AND ECMWF ENSEMBLE
MEAN MAINTAINS BETTER PRODUCT CONTINUITY AND STRENGTH.
..WEATHER/HAZARDS HIGHLIGHTS
THE THREAT FOR EXCESSIVE RAINFALL IS FORECAST TO REMAIN LOW
TUESDAY. HOWEVER, MOISTURE WORKING INTO THE PACIFIC NORTHWEST
AHEAD OF AN APPROACHING FRONTAL SYSTEM WILL COMBINE WITH UPPER
LEVEL DYNAMIC SUPPORT AND TERRAIN UPSLOPE TO ENHANCE RAINFALL FOR
THE COASTAL MOUNTAIN RANGES, OLYMPICS, AND CASCADES THAT WILL
LIKELY SEE THE HIGHEST RAINFALL TOTALS. A MARGINAL RISK OF
EXCESSIVE RAINFALL WAS NOT INTRODUCED AS THE SYSTEM SEEMS
PROGRESSIVE AND MUCH OF THE PACIFIC NORTHWEST HAS LINGERING
DROUGHT CONDITIONS, SO MUCH OF THIS RAINFALL COULD BE MORE
BENEFICIAL THAN HAZARDOUS. HIGHER ELEVATIONS FROM THE CASCADES
THROUGH THE NORTHERN ROCKIES WILL SEE SNOW WITH UPPER
TROUGH/HEIGHT FALL APPROACH AND PASSAGE.
PRECIPITATION CHANCES WILL EXPAND EAST THROUGHOUT THE WEEK AS A
FRONTAL SYSTEM MOVES ACROSS THE NATION, REACHING THE CENTRAL U.S.
BY AROUND MIDWEEK. DEEP CYCLOGENESIS AND WRAPPING MOISUTRE INTO A
LEADING WARM FRONT LIFTING THROUGH THE EAST-CENTRAL U.S. WILL
SHIFT FOCUS FOR POSSIBLY HEAVY RAIN FROM THE CENTRAL PLAINS
THROUGH THE MIDWEST INTO WEDNESDAY. THE WPC DAY 5 EXCESSIVE
RAINFALL OUTLOOK (ERO) PLANS TO SHOW A MARGINAL RISK OVER THE
MID-MS VALLEY GIVEN RISK FOR TRAINING AND GROWING MODEL AND
ENSEMBLE SIGNALS. GUIDANCE SUGGESTS THIS HEAVY RAINFALL AREA WILL
LIKELY EXPAND THURSDAY ACROSS THE MIDWEST WITH CONTINUED SYSTEM
DEVELOPMENT AND TRACK/INFLOW. MEANWHILE WELL SOUTH, A SEPARATE
WARM FRONT LIFTING THROUGH THE GULF OF MEXICO AND THE FLORIDA
PENINSULA BRINGS A THREAT FOR HEAVY RAINFALL FROM THE CENTRAL GULF
COAST TO THE SOUTHEAST WEDNESDAY/THURSDAY. THIS MAY BE AIDED BY AN
AREA OF LOW PRESSURE IN THE GULF OF MEXICO AND POSSIBLE REMNANT
TROPICAL MOISTURE TO BE MONITORED IN THE COMING DAYS. WHILE NO DAY
5/WEDNESDAY ERO HAS BEEN ISSUED GIVEN SYSTEM UNCERTAINTIES AND
TIMING, RAINFALL POTENTIAL WILL LIKELY WARRANT ERO RISK
CONSIDERATION BY THURSDAY. THESE TWO MAIN SYSTEMS MAY INCREASINGLY
INTERACT TO SPREAD ENHANCED RAINFALL AND RUNOFF ISSUES POSSIBLE
ACROSS THE EAST/NORTHEAST FRIDAY INTO SATURDAY, WITH WIDESPREAD
ENHANCED BACKSIDE WINDS AND POST-FRONTAL FALLING AUTUMN
TEMPERATURES.
SCHICHTEL
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 FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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