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Area Forecast Discussion
354 FXUS62 KCHS 292000 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 400 PM EDT FRI JUL 29 2016 .SYNOPSIS... Atlantic high pressure along with an inland trough will prevail into early next week. High pressure will then become suppressed further to the south which could allow a weak cold front to approach from the north by the middle part of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... This Evening and Tonight: A large mid/upper lvl ridge of high pressure will become more elongated across the southeastern United States while a broad trough of low pressure extends over the Midwest and Northeast. The pattern will result in mainly dry conditions within a light west/southwest flow through the overnight period. Temps will remain quite warm overnight...only dipping into the mid/upper 70s inland to lower 80s along the coast. Record high minimums will be possible. (See CLIMATE section below). && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... Saturday and Saturday night: The synoptic pattern will consist of a strong ridge over the Southeast U.S. and a trough inland. Computer models indicate the ridge will weaken slightly and it`s axis will become more focused across southern GA and FL. This will allow the trough inland to strengthen a bit and shift closer to the coast, resulting in slightly better convective chances during the afternoon and evening (as compared to what we`ve been seeing for the past few days). Model profiles are still not too impressive. However, moisture/instability should be decent enough to generate some convection. The best coverage should be in the Charleston Tri- County area, further north and away from the ridge axis. Highs will remain above normal, in the mid to upper 90s. Lows will be in the mid to upper 70s inland and lower 80s closer to the coast. Minimal, if any, precipitation is expected over land at night. But some convection could develop over the coastal waters with the land breeze. Sunday through Monday: Aloft, the forecast area will be solidly sandwiched between broad troughing to the north and the upper ridge to the south. Through early next week, the inland trough looks to be increasingly active and with modestly better sounding profiles across the forecast area this should result in a much more typical coverage pattern for thunderstorms. POPs are generally in the 30-50% chance range. The overall severe threat doesn`t look particularly high. Temperatures may come down a few degrees into the mid 90s, but with dew points still in the low to mid 70s heat index values will still be in the 100-105 degree range. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... In the long term period through Thursday, the relatively broad trough will finally break down much of the upper ridge with it splitting into one part over the south-central CONUS and the other over the Atlantic. Towards the end of the period the orientation of the ridge to the west will help turn the large scale flow more northwesterly across the area which may allow for more embedded shortwave energy to approach the area. As such, we may need to keep more of an eye on upstream convection and how it evolves and potentially heads into the region. Overall convection changes are higher through this period, thanks in part to the presence of a weak front situated to the north and the slightly cyclonic flow aloft. Also of note, temperatures should exhibit a slight cooling trend with primarily low 90s by Thursday. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... VFR conditions are expected at both CHS and SAV terminals through 18z Saturday. Winds should gust around 20 kt early this afternoon at the CHS terminal, mainly due to deep mixing associated with warm afternoon temps. Extended Aviation Outlook: Brief flight restrictions are possible with afternoon/evening showers/thunderstorms Sunday through Wednesday. Otherwise, VFR will prevail. && .MARINE... Tonight: Atlantic high pressure will dominate the coastal waters while a sfc trough persists inland. The setup will support a southwest wind mainly between 15-20 kt. We could also see an hour or two of 25 kt wind gusts with some nocturnal surging. However, given 1000mb geostrophic flow is projected to be at or below 15-20 kt through the overnight period, winds should remain just below Small Craft Advisory levels. Seas will range between 2-4 ft. Saturday through Wednesday: Atlantic high pressure interacting with a trough inland will allow S to SW winds to prevail. Expect morning lulls in the winds followed by slight increases associated with the development of the sea breeze each afternoon. Evening and overnight winds should be the strongest, in the 15-20 kt range. Seas will average 1-3 ft, with some 4 footers possible around 20 nm and beyond during the times of the strongest winds. && .CLIMATE... Record high minimums for 29 July... KCHS: 80 set in 1999. KCXM: 85 set in 1999. KSAV: 82 set in 1878. Record high maximums for 29 July... KCHS: 100 set in 1993. KCXM: 99 set in 1999. KSAV: 103 set in 1993. Record high minimums for 30 July... KCHS: 80 set in 2011. KCXM: 82 set in 1999 and previous. KSAV: 81 set in 1878. ***Top 5 Warmest Months on Record by Average Temperature*** Charleston International Airport - KCHS (Records Back to 1938) 1. 86.1 - July 1986 2. 85.9 - July 2016 (3 days left) 3. 85.5 - July 1993 4. 83.9 - July 1992 5. 83.8 - July 1998 Savannah International Airport - KSAV (Records Back to 1874) 1. 86.7 - July 1993 2. 85.9 - July 2016 (3 days left) 3. 85.7 - July 1986 4. 85.7 - July 1875 5. 84.8 - August 2011 ***Top 5 Driest Months on Record for July*** Savannah International Airport - KSAV (Records back to 1871) 1. 0.82 - 1888 2. 1.21 - 2016 (3 days left) 3. 1.25 - 1881 4. 1.33 - 1949 5. 1.35 - 1972 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...DPB SHORT TERM... LONG TERM... AVIATION...DPB MARINE...DPB CLIMATE...