762 FXUS62 KCHS 070846 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 446 AM EDT Wed Aug 7 2019 .SYNOPSIS... A weak surface trough will prevail inland while high pressure persists across the Atlantic through Friday. A cold front will approach from the north Saturday, then become stationary over or near our area early next week. && .NEAR TERM /THROUGH TONIGHT/... Pre-dawn: Warm and humid early morning conditions with low-level southwest flow resulting in enough mixing to keep temps inland in the mid 70s with upper 70s common along the coast at 4 AM. Mostly clear skies likely to prevail with some patchy layered clouds lingering over a few spots. Today: Little change to the synoptic pattern today with the deep- layer trough in place. The morning hours are expected to be mainly dry with a weak cap in place and strong surface heating occurring, sending temps to around 90 degrees many areas by midday. This afternoon, we expect convection will be slow to develop as the upper jet position favors some broad sinking aloft with mid level drying was noted on time/height cross- sections. In the 18Z-21Z time, the majority of CAMs suggest on isolated coverage across the area and we have maintained only a slight chance POP. In the 22Z-02Z time frame, a weak short wave will push through the coastal Carolinas and we have some chance POPs across the northern SC zones and Charleston Tri-County area as moisture is forecast to pool along the sea breeze. Strong updraft potential looks to be north of the area during this time period but isolated stronger storms cannot be ruled out if convection develops earlier in the evening. It will continue to warm today with low to mid 90s common with heat indices in the 100-103 degree range most areas. Tonight: Isolated showers and tstms may occur late evening prior to the low level flow veering west after midnight with the formation of the land breeze and passing of the mid level disturbance. Low will be in the lower to mid 70s. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... The mid-levels will consist of a trough just off the Southeast coast Thursday morning. It will gradually move offshore and weaken/deamplify into Saturday as ridging builds over the Central U.S., leading to northwest flow over our area. At the surface, a weak surface trough will prevail inland while high pressure persists across the Atlantic through Friday. A cold front will approach from the north on Saturday. The downward trend in moisture continues with PWATs falling to roughly 1.5-1.75" Thursday and Friday. Likewise, models show much less convective potential Thursday and Friday. We lowered the POPs further, keeping slight chance areas to south of the Charleston Tri-County area. The best potential for convection should be along the GA coast each afternoon for a few hours. Though, drier air in the mid-levels may keep a more of the area capped and dry than what we're currently showing. During this time frame, 850 mb temperatures and a late push by the sea breeze will lead to daytime temperatures several degrees above normal and mild low temperatures. Saturday moisture ramps up quickly ahead of the front with PWATs exceeding 2". Likewise, we have POPs ramping up into the chance category, especially across our GA counties. It's still a little early to determine the convective potential. Instability should be in place, aided by lift from the approaching front and maybe the sea breeze. However, DCAPEs are not too high, which will limit the wind potential. Locally heavy rainfall is also possible. But the flooding threat may be limited somewhat by the steering winds aloft. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... Mid-level troughing will be moving off the East Coast and deamplifying Saturday night into Sunday. Meanwhile, ridging will be building over the Central U.S., with High pressure centered over the Southern Plains. These features will start creeping towards the Southeast on Monday while weakening. This should lead to semi-zonal flow over our area on Tuesday. At the surface, a stationary front will be spread across or nearby our area Saturday night into Sunday. The front should dissipate on Monday. Models have trended the front further to the north, which was expected. This equates to more persistent showers/thunderstorms for much of the long term. Though, a shift further north by the front could lead to a slightly drier forecast. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... VFR conditions will prevail at KCHS/KSAV through much of Wednesday. Brief flight restrictions are possible due to showers and/or thunderstorms developing across the area Wednesday afternoon/evening, but confidence remains too low to include mention in the 06Z taf issuance. Extended Aviation Outlook: A front could bring afternoon/evening flight restrictions this weekend. && .MARINE... After a decent nocturnal surge of southwest flow overnight, winds were subsiding as daybreak nears and will continue to subside until the flow begins to increase along the SC beaches and points offshore after mid afternoon. The surging across the waters will peak during the evening and early overnight period all waters before late night ebbing. Speeds will reach 15-20 kt with seas 3-4 ft on average. Extended Marine: No Small Craft Advisories are expected in the extended forecast. The surface pattern will consist of a weak surface trough inland while high pressure persists across the Atlantic through Friday. A cold front will approach from the north Saturday, then become stationary over or near our area early next week. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...MS LONG TERM...MS AVIATION...MS MARINE...MS