Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 210149 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 949 PM EDT Sat Jul 20 2019 .SYNOPSIS... The area will remain situated between an inland trough and Atlantic high pressure into early next week. A cold front is expected to stall over or close to the region by the middle of next week, then linger into late week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Late Saturday evening: Isolated/scattered showers/thunderstorms developing along mesoscale boundaries south of the Altamaha River should spill into counties south of Interstate 16 before dissipating by midnight or shortly thereafter. Aside from adjusting PoPS to account for convection across far southern counties, ongoing rain-free along/north of I-16 remain generally on track for the remainder of the night. Low temperatures will range from the lower to middle 70s inland to around 80F near the coast. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/... Sunday: Aloft, ridging will prevail for another day with the same surface setup featuring a trough inland and high pressure to the east. Model soundings look at least a little more conducive to convection than they do for today (Saturday). We should be able to get isolated showers and thunderstorms, but convection should remain on the weaker end of the spectrum. Temperatures should rise into the mid 90`s, with some locations pushing the upper 90`s. Heat index values should top out around 105. Overnight, any lingering convection should diminish during the evening and the rest of the period should be dry. Lows are forecast for the low/mid 70`s inland and the upper 70`s along the coast. Monday: The upper ridge will weaken and start to be replaced by the southern end of a longwave trough pushing into the eastern half of the CONUS. Overall, the surface will Outflow from earlier convection could cross the Altamaha River and produce a shower/thunderstorm this evening. However, the prospects for measurable precipitation appear meager, thus lowered inland PoPs to less than 15 percent with no mention of showers. Otherwise, tranquil forecasts remain on track and required no significant changes. Mid-level ridging will persist through the night. At the surface, our area will remain in between an inland trough and Atlantic high pressure. PWATs are about 1.8", which is near normal for this time of year. However, all of the synoptic models and the CAMs are in great agreement showing a dry night. This is due to strong mid-level capping and the lack of any mesoscale lift. Other than some cumulus clouds early in the evening, the overnight hours will be dry and mostly clear. Lows should be in the 70s, which is near normal.remain unchanged with the inland trough and subtropical high. A cold front will begin to approach from the northwest late in the day, but shouldn`t have any impact on the forecast for another 24 hours or so. Convection should be similar to Sunday and the forecast features rain chances in the 20-30 percent range, highest along the southeast Georgia coast. Overnight, modestly better chance of seeing some nocturnal showers, mainly across the coastal waters. Instead of a dry forecast we have 20-30 percent chances overnight. Tuesday: The trough aloft will solidly encompass the eastern seaboard and the front will finally push into Georgia and the Carolinas. The first part of the day could end up being quiet before convection develops upstream and drops into the forecast area later in the day. Could even see some degree of a severe threat depending on how organized convection can become. For now, the forecast continue to feature rain chances in the 50-60 percent range. Will have to see how cloud cover evolves and the impact on temperatures. Currently we show mostly low 90`s, but this could be a bit underdone if the bulk of the convection holds off until later in the day. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Likely POPs in order Tuesday night just ahead of the surface cold front and mid level short wave. The front is forecast to stall along the southeast coast during mid to late week. Broad upper troughing will deliver a favorable medium for unsettled weather across the forecast area during this period. Bouts of scattered to numerous showers and tstms are expected Wednesday and perhaps again Thursday. Model agreement on the frontal position wanes by late week with the boundary tending to wash out by early next weekend. We maintained POPs slightly greater than climo for this period. Temps will be tempered by a good bit of cloud cover along with chances for convective rains mid to late week. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... VFR through Sunday. The chance for direct impacts from isolated thunderstorms Sunday afternoon remains too low to justify any mention within 00z TAFs. Extended Aviation Outlook: Brief flight restrictions could occur within thunderstorms, especially during the afternoon/evening hours Sunday and Monday. The chance for thunderstorms/associated flight restrictions are expected to increase Tuesday afternoon and evening ahead of a cold front. Scattered to occasionally numerous showers and tstms are expected in the vicinity of a stalled front during mid/late week. && .MARINE... Overnight: Expect south to southwest winds to average 15-20 knots along with seas of 2-3 ft. A couple of thunderstorms could push into GA marine zones through midnight, then the remainder of the night should remain rain-free. Sunday through Thursday: South to southwest flow will prevail through Tuesday as the local waters sit between the inland trough and high pressure to the east. Wind speeds will continue to be enhanced at times, surging into the 15-20 knot range but should remain below Small Craft Advisory levels. Seas should average 2-4 feet. Then for Tuesday night through Thursday, a cold front is expected to stall out over or near the local waters mid to late week. A weak gradient should result in light winds and seas in the 2 ft range. We also expect showers and tstms to increase in coverage during this time frame. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...SPR SHORT TERM... LONG TERM... AVIATION...SPR MARINE...SPR is the U.S. government's official web portal to all federal, state and local government web resources and services.