870
FXUS02 KWBC 040657
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT MON SEP 04 2023
VALID 12Z THU SEP 07 2023 - 12Z MON SEP 11 2023
...IMPRESSIVE HEAT TO SHIFT FROM THE EAST/SOUTH TO THE
SOUTH-CENTRAL U.S AND SOUTHWEST...
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
BROAD COMPOSITE BLEND OF BEST CLUSTERED OVERALL GUIDANCE FROM THE
18 UTC GFS/GEFS MEAN AND THE 12 UTC ECMWF/ECMWF ENSEMBLE MEAN
ALONG WITH THE COMPATIBLE 01 UTC NATIONAL BLEND OF MODELS IN A
PATTERN WITH SEEMINGLY ABOVE NORMAL MID-LARGER SCALE
PREDICTABILITY. THIS BLEND TENDS TO BEST MITIGATE WIDESPREAD
SMALLER SCALE WARM SEASON GUIDANCE DIFFERENCES GENERALLY
CONSISTENT WITH SYSTEM PREDICTABILITY AND MAINTAINS GOOD WPC
CONTINUITY. A COMPOSITE OF GUIDANCE FROM THE LATEST 00 UTC
GUIDANCE CYCLE OVERALL REMAINS IN LINE.
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
THE EMERGENCE OF AN AMPLIFIED UPPER TROUGH THROUGH THE MIDWEST
INTO THURSDAY/FRIDAY WILL ACT TO SUPPRESS UPPER RIDGING AND HIGH
HEAT ACROSS THE EAST. UPPER TROUGHING WILL SETTLE OVER THE EAST
THROUGH THE WEEKEND AS ANCHORED BY AN UPPER LOW OVER HUDSON BAY
AND AS A SERIES OF WEAKER IMPULSES RIDE OVER THE TOP THEN TO THE
LEE OF THE TRANSITIONING UPPER RIDGE AS IT STRENGTHENS OVER THE
SOUTH/SOUTHWEST. HOT LATE SUMMER TEMPERATURES LINGERING ACROSS THE
EAST AND SOUTHEAST INTO THURSDAY WILL ACCORDINGLY REFOCUS TO THE
SOUTH-CENTRAL U.S. AND THE SOUTHWEST THROUGH THE WEEKEND INTO NEXT
WEEK WITH THE REPOSITIONING OF THE UPPER RIDGE. TEMPERATURE
ANOMALIES UPWARDS TO THE 10-15 DEGREES ABOVE NORMAL RANGE OFFERS
POTENTIAL FOR WIDESPREAD RECORD VALUES (BOTH DAILY RECORDS AND
POSSIBLY SOME MONTHLY RECORDS) IN WHAT HAS PROVEN TO BE A
SWELTERING SUMMER.
MEANWHILE IN THIS PATTERN, EXPECT A MAIN ORGANIZED/MAINLY MODERATE
OVERALL PRECIPITATION FOCUS WILL BE ASSOCIATED WITH THE UPPER
TROUGHING OVER THE EAST WITH FUELING MOISTURE AND INSTABILITY INTO
A LEADING SURFACE LOW/FRONTAL SYSTEM LATER WEEK INTO THE WEEKEND.
SOME LOCALIZED HEAVY CONVECTIVE DOWNPOURS WILL ALSO OCCUR IN
SCATTERED/PERIODIC CONVECTION BACK TO/ACROSS SOUTHERN TO CENTRAL
STATES NEAR A WAVY TRAILING FRONT IN A PATTERN WITH FAVORABLE
UPPER DIFLUENCE AND PERIODIC IMPULSE PASSAGES. THIS OCCURS AS AN
UNCERTAIN SERIES OF SHORTWAVES WORK FROM THE PACIFIC THROUGH THE
WEST/NORTHWEST AND INLAND ACROSS THE INTERMOUNTAIN WEST/ROCKIES
THOUGH THE PERIOD, ALBEIT IN A PATTERN WITH LIMITED PRECIPITATION
BUT LOCALIZED CONVECTION THAT MAY BECOME MODESTLY ORGANIZED THIS
WEEKEND ACROSS THE NORTHERN ROCKIES BEFORE WORKING INTO THE
CENTRAL U.S. STATES. WHILE NO WPC EXCESSIVE RAINFALL AREAS HAVE
BEEN ISSUED FOR THE DAY 4/5 PERIOD THURSDAY/FRIDAY AT THIS TIME
GIVEN UNCERTAINTIES AT THESE LONGER TIME FRAMES FOR SUMMER
CONVECTION, THERE IS A GUIDANCE TREND SUGGESTING A FEW SLOWER
TRAINING CELLS MAY OFFER A THREAT FOR SOME RUNOFF ISSUES OVER THE
MID-SOUTH AND VICINITY.
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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