


Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
721 FXUS62 KCHS 080517 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 117 AM EDT Tue Jul 8 2025 .SYNOPSIS... Weak high pressure will extend across the area through the week. && .NEAR TERM /THROUGH TONIGHT/... Today: The synoptic pattern has changed little since yesterday with deep-layered subtropical ridging over the Atlantic extending west across the Southeast U.S. while a mid-level weakness persists across the lower Mississippi Valley. This will maintain a typical summertime southwest flow regime in place with another resultant sea breeze circulation poised to push inland this afternoon. The resultant looks to push in a bit faster compared to yesterday, likely owing to a bit more southwest flow atop the boundary layer. Modified forecast soundings suggest convective temperatures may be about 1-2 degrees lower than Wednesday so convection may initiate a bit faster. Simulated reflectivity progs off a number of the CAMS support this trend. 08/01z NBM hourly pops were utilized with rain chance maxing out in the 30-60% range, highest across the interior. These values look within reason based on the latest HREF. The atmosphere has changed little with modified soundings showing weak shear persisting within a relatively weak wind environment, especially inland. Convection will therefore remain fairly slow moving with convective outflow propagation and other mesoscale boundary interactions likely dominating localized cell movements. Thermodynamically, modified soundings continue to show an environment favorable for an isolated pulse severe tstm or two with a risk for damaging winds from wet microbursts. Frequent cloud-to-ground lightning and locally heavy rainfall capable of producing minor flooding in low-lying and poor drainage areas are also possible. It will be another warm day with 1000-850 hPa thicknesses and 850 hPa temperatures similar to Tuesday`s values. However, the combination of a possible earlier start to convection and a bit more coverage suggests temperatures may not be quite as warm. Still expect highs to warm into the lower-mid 90s away from the beaches with possibly a few upper 90s occurring well inland, especially over far interior Southeast Georgia. Such warm temperatures will support another round of significant dewpoints mixing during peak heating. Dewpoints look to mix out in the upper 60s/near 70 well inland while holding in the lower 70s east of I-95. Another round of moisture pooling near the near/behind the sea breeze will help surge dewpoints into the mid-upper 70s with a few 80 degree readings possible along the Charleston County coast. Heat indices will peak in the 102-105 range for most areas with 105-108 occurring across parts of the Charleston Tri-County area near the sea breeze. This is generally below Heat Advisory criteria (108-112 for at least 2 hrs), although a few spots along and just east of the US-17 corridor in Charleston County up into the Francis Marion National Forest could briefly exceed 108, which includes Downtown Charleston. For the Charleston Tri-County area, neighborhood probabilities for heat indices exceeding 108 are 10-30% depending on location. Tonight: Convection will linger across the interior through about mid-evening before dissipating with the loss of insolation. Lows will range from the mid 70s well inland to the mid-upper 70s across the coastal counties with lower 80s at the beaches and Downtown Charleston. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... The surface pattern will feature high pressure offshore with a weak trough of low pressure across the Appalachians. Aloft, subtle ridging will erode Wednesday as a shortwave begins its track across the Tennessee Valley. A sea breeze pattern will dominate through the period, although some upper forcing could spread in from the north. Scattered to possibly numerous showers and thunderstorms are possible each day through Friday, mainly in the afternoon and evening when instability is maximized. There is no shortage in moisture content noted via PWATs above 2.2" and model soundings showing close to saturated upper levels. This could lead to heavy downpours within storms. Additionally, little steering flow, especially Wednesday, could result in quick bouts of rainfall and minor/nuisance flooding. High temperatures will reach the upper 80s at the beaches and low 90s elsewhere both Wednesday and Thursday. Friday could see highs about 1-2 degrees warmer, approaching the mid 90s. Overnight lows both Wednesday and Thursday night will remain in the low/mid 70s away from the coast, and upper 70s at the beaches. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... The slightly eroded upper ridge to our east will build back over the Southeast through the weekend and into early next week. Otherwise, little change expected in the overall synoptic pattern and the forecast. Typical diurnal convection will continue with scattered showers and thunderstorms forming each day in the afternoon/evening. Highs will be above normal, reaching the mid 90s most places over the weekend. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/... 08/06z TAF Discussion: KCHS/KSAV/KJZI: VFR will prevail for much of the period. Scattered showers/tstms are expected to develop near/ahead of the afternoon sea breeze. Some of this may brush KCHS and KSAV before focusing west of the terminals by mid-late afternoon. Impact probabilities are too low to justify a mention at this time, but the need for TSRA will be reevaluated with the 12z TAF cycle. Extended Aviation Outlook: Brief ceiling/vsby restrictions possible due to scattered showers and thunderstorms. && .MARINE... Through Tonight: Southwest winds will back to the south this afternoon with the afternoon sea breeze with southerly winds holding through the night. Speeds will generally range from 10-15 kt, but will be closer to 15 kt with gusts to 20 kt near the land/sea interface and Charleston Harbor near and behind the sea breeze. Seas will average 2-3 ft. Wednesday through Sunday: Relatively benign conditions are forecast and as a result there are no marine concerns during the period. South to southwest flow will persist with high pressure to the east. Wind speeds will be 15 kt or less and seas will average 2-3 ft, with some 4 foot seas moving in at times Thursday and Friday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$