429
FXUS02 KWBC 070651
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 AM EDT THU SEP 07 2023
VALID 12Z SUN SEP 10 2023 - 12Z THU SEP 14 2023
...HAZARDOUS HEAT FROM THE SOUTH-CENTRAL U.S TO THE SOUTHWEST TO
MODERATE NEXT WEEK...
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF REASONABLY WELL CLUSTERED GUIDANCE OF THE 18
UTC GFS AND 12 UTC ECMWF/UKMET/CANADIAN MODELS ALONG WITH THE 01
UTC NATIONAL BLEND OF MODELS SUNDAY-TUESDAY. ADDED INPUT FROM THE
COMPATIBLE 18 UTC GEFS MEAN AND 12 UTC ECMWF ENSEMBLE MEAN AT
LONGER TIME FRAMES AMID SLOWLY GROWING FORECAST SPREAD. EVEN SO,
MID-LARGER SCALE PREDICTABILITY REMAINS ABOVE NORMAL. THESE
COMPOSITE BLENDS TEND TO MITIGATE MUCH OF THE LESS PREDICTABLE
SMALLER SCALE VARIANCES CONSISTENT WITH UNCERTAINTY. WPC PRODUCT
CONTINUITY IS WELL MAINTAINED IN THIS MANNER AND LATEST GUIDANCE
FROM THE 00 UTC MODEL CYCLE GENERALLY REMAINS CONSISTENT.
..WEATHER/HAZARDS HIGHLIGHTS
HAZARDOUS LATE SUMMER HEAT WILL LINGER ACROSS THE SOUTH-CENTRAL
U.S. AND THE SOUTHWEST UNDER A POTENT UPPER RIDGE INTO MONDAY.
HIGH DEWPOINTS AND HUMIDITY ESPECIALLY NEAR THE WESTERN GULF COAST
WILL LEAD TO DANGEROUS HEAT INDICES AS HIGH AS 115 DEGREES WITH
TEMPERATURES AS ELEVATED AT 10-15 DEGREES ABOVE NORMAL. EXPECT
WIDESPREAD RECORD HIGH MINIMUM AND MAXIMUM TEMPERATURES WILL BE
SET. UPPER-LEVEL ENERGY TRENDING SOUTHWARD WILL ACT TO REDUCE
RIDGE STRENGTH AND BEGIN TO BRING TEMPERATURES TO STILL HOT BUT
MORE REASONABLE LEVELS ONWARD NEXT WEEK.
MEANWHILE, AMPLIFIED UPPER TROUGHING WILL SETTLE OVER THE EASTERN
THIRD OF THE NATION THROUGH THE WEEKEND INTO NEXT WEEK AS A SERIES
OF IMPULSES ROUND THE AFOREMENTIONED UPPER RIDGE AND AS NORTHERN
STREAM ENERGIES DIG SOUTHEASTWARD FROM A WEST-CENTRAL CANADIAN
UPPER RIDGE. IN THIS PATTERN, THE NORTHERN MID-ATLANTIC AND THE
NORTHEAST OFFER A MAIN AREA FOR PRECIPITATION TO FOCUS, GIVEN
HIGHER PRECIPITABLE WATER VALUES THAN AVERAGE AND INSTABILITY
POOLING AHEAD OF THE UPPER TROUGH AND WAVY SURFACE FRONTAL SYSTEM.
INGREDIENTS WILL BE IN PLACE FOR LOCALIZED HEAVIER RAIN TOTALS AS
STORMS MAY BE SLOW-MOVING AND RELATIVELY PARALLEL TO THE FRONT,
ALLOWING FOR POTENTIAL TRAINING OF STORMS.
THE WPC DAY 4/5 EXCESSIVE RAINFALL OUTLOOKS (EROS) DENOTE
"MARGINAL" RISK AREAS FROM THE NORTHERN MID-ATLANTIC ACROSS
NORTHERN NEW ENGLAND SUNDAY INTO MONDAY AS CONVECTION LOOKS TO
HAVE A RELATIVELY BETTER FOCUS NEAR THE FRONT AND FAVORABLE RIGHT
ENTRANCE REGION UPPER JET SUPPORT. GUIDANCE HAS ALSO TRENDED TO A
MORE ORGANIZED MAIN FRONTAL WAVE TO WRAP IN ATLANTIC MOISTURE. THE
"MARGINAL" RISKS ENCOMPASS RELATIVELY LOWER FFGS AND INCLUDES
FAVORED TERRAIN FROM THE POCONOS AND CATSKILLS TO THE ADIRONDACKS
AND THE GREEN/WHITE MOUNTAINS. RAIN CHANCES SHOULD GRADUALLY
DECREASE AFTER MONDAY ALONG THE EASTERN SEABOARD AS THE WAVY
FRONTS PUSH EAST OFF THE COAST.
UPSTREAM, AN AMPLIFIED SYSTEM WILL SKIRT THE PACIFIC NORTHWEST
SUNDAY TO SUPPORT MODEST COASTAL SHOWERS. UNDERNEATH, A SERIES OF
LESS DEFINED SOUTHERN STREAM SHORTWAVES WILL WORK INLAND ACROSS
THE WEST COAST AND INTERMOUNTAIN WEST IN A PATTERN WITH LIMITED
PRECIPITATION THIS WEEKEND AND NEXT WEEK. THIS ENERGY WILL WORK
DOWNSTREAM TO THE NORTH-CENTRAL ROCKIES AND DIG INTO THE PLAINS TO
SUPPORT MORE WIDESPREAD AND LOCALLY STRONG TO SEVERE CONVECTION,
WHERE SOME HEAVY RAIN TOTALS ARE EXPECTED LOCALLY UNDER FAVORABLE
UPPER DIFLUENCE AND POTENTIAL CELL TRAINING. THE WPC DAY 4/SUNDAY
AND DAY 5/MONDAY EROS DENOTE "MARGINAL" RISK AREAS SPREAD FROM THE
CENTRAL TO SOUTHERN PLAINS.
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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