Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 180847 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 347 AM EST Thu Jan 18 2018 .SYNOPSIS...
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Cold, dry high pressure will build over the region today and tonight before moderating temperatures occur this weekend into early next week. A cold front will push through the area late Monday into early Tuesday, followed by dry high pressure into mid week. A low pressure system could approach the area during the second half of the week.
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&& .NEAR TERM /THROUGH TODAY/...
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Through Sunrise: Low clouds and wrap around moisture in the form of scattered flurries have finally scoured out of the Charleston Tri-County area as low pressure near the North Carolina Outer Banks deepens. The risk for flurries has ended and no additional precipitation will occur this morning. Brisk northwest winds coupled with temperatures falling well into the 20s will produce wind chills 11-16 degrees over the next few hours. A Wind Chill Advisory remains in effect through 8 am for the coastal counties (criteria 15 degrees). Could see some spots touch minimum wind chills around 10 degrees over portions of northern Dorchester and Berkeley Counties prior to daybreak so will have to monitor this area for a possible expansion of the Wind Chill Advisory into these zones (inland criteria 10 degrees). Today: The upper-level flow will gradually become zonal today as the deep upper trough exits off the Eastern Seaboard. Cold high pressure with arctic origins will extend across the region through tonight. Sunny and dry conditions will prevail with highs ranging from the mid 40s across Southeast South Carolina to the upper 40s over Southeast Georgia. Could see a few spots north of the I-26 corridor only top out in the lower 40s, but these should remain fairly isolated. Breezy conditions this morning will diminish by afternoon as the pressure gradient between inland high pressure and exiting low pressure gradually relaxes.
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&& .SHORT TERM /TONIGHT THROUGH SUNDAY/...
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Tonight: It will be another cold winter night for the Lowcountry and Coastal Empire. Although the center of the arctic high is forecast to remain over the Deep South, a surface ridge will extend east across southern Georgia into south coastal South Carolina as a weak lee-side trough induced by westerly flow atop the southern Appalachians remains pinned to the Upstate and North Carolina Foothills. Light to calm winds within the surface ridge, very low dewpoints and clear skies will promote strong radiational cooling with temperatures expected to bottom out in the lower-mid 20s inland with mid-upper 20s at the coast. Could see a few upper teens in some of the normally colder locations. Friday through Sunday: Dry high pressure will become centered over the area Friday, helping produce noticeably warmer conditions under sunny skies and weak ridging aloft. In general, temps should peak in the mid 50s. Strong radiational cooling under clear skies will favor Friday night lows in the upper 20s/lower 30s away from the coast. A mid/upper lvl low is then expected to traverse the Southeast on Saturday, but moisture will be very limited, especially in the lower levels where dry high pressure remains. Given the setup, some mid/upper lvl clouds are possible as the disturbance passes aloft, but precip is not anticipated. Temps should also be warmer on Saturday as the atmosphere continues to modify and a light southwest develops during the afternoon. In general, highs should peak in the lower 60s Saturday afternoon. Saturday night lows should dip into the mid/upper 30s. Dry high pressure will persist over the Southeast on Sunday. Abundant sunshine will likely produce another day of warmer temps with afternoon highs peaking in the mid 60s away from the immediate coast.
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&& .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
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High pressure will prevail over the Southeast United States into early next week before a cold front arrives late Monday into early Tuesday. Ahead of the front, southerly winds will help advect deep moisture characterized by PWATs around 1.3 inches to the Southeast and result in some cloud cover. This could limit overall heating potential a few degrees, but temps are still expected to peak in the upper 60s/lower 70s Monday afternoon. Chances of showers should then spread over inland areas Monday afternoon/evening before advancing to the coast with the cold front Monday night. Dry high pressure will then return behind the departing front on Tuesday and persist into the middle of next week. Temps will be slightly cooler behind the front, but should remain a few degrees above normal. In general, afternoon temps should peak in the lower 60s away from the immediate coast. Overnight lows should dip to around 40 degrees inland and mid 40s closer to the coast. The next best chance of precip is possible on Thursday as a low pressure system passes south of region.
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&& .AVIATION /07Z THURSDAY THROUGH MONDAY/...
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Primary concern: * timing of VFR at KCHS Satellite shows low clouds gradually scouring out as low pressure deepens off the North Carolina coast. Expect MVFR cigs will linger at KCHS through about 08-09z with VFR prevailing thereafter. VFR at KSAV. Extended Aviation Outlook: Flight restrictions are possible at both KCHS and KSAV terminals late Monday as rain develops along a passing cold front.
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&& .MARINE...
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Today: Nasty conditions across the marine area this morning will gradually improve through the day as cold air advection wanes and the pressure gradient relaxes. The Small Craft Advisory will remain in force for all nearshore legs through 7 am with the Charleston County waters holding on through late morning. Seas will remain elevated enough over the Georgia offshore waters to keep the advisory in place there through late afternoon. Tonight: Northwest winds will gradually back to the west overnight as a surface ridge builds east out of the Deep South and into southern Georgia into south coastal South Carolina. Winds will remain less than 15 kt with seas subsiding to 1-2 ft nearshore and 2-3 ft offshore. Friday through Tuesday: Dry high pressure will prevail over the coastal waters this weekend into early next week with winds/seas remaining well below Small Craft Advisory levels. In general west/northwest winds will remain at or below 10-15 kt through Sunday while seas are no higher than 2-3 ft. On Monday, a southerly wind will develop ahead of a cold front approaching from the west late Monday into early Tuesday. Winds should approach 15-20 kt while seas build up to 3-4 ft with fropa. However, Small Craft Advisories are not anticipated.
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&& .EQUIPMENT... The KCLX radar is out of service until further notice. Repairs are ongoing. Adjacent radars include: KLTX, KCAE, KJGX, KVAX and KJAX. The Downtown Charleston observation site (CHLS1/KCXM) remains out of service until further notice. && .CHS WATCHES/WARNINGS/ADVISORIES...
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GA...Wind Chill Advisory until 8 AM EST this morning for GAZ116>119- 137>141. SC...Wind Chill Advisory until 8 AM EST this morning for SCZ048>052. MARINE...Small Craft Advisory until 7 AM EST this morning for AMZ330- 352-354. Small Craft Advisory until 10 AM EST this morning for AMZ350. Small Craft Advisory until 4 PM EST this afternoon for AMZ374.
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&& $$

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