textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated to reflect the 00Z TAFs.

KEY MESSAGES

- 1) Dry conditions and seasonable temperatures expected this week. Colder conditions this weekend.

- 2) Freezing temperatures are possible across far inland areas Friday night, followed by a potential widespread freeze Saturday night.

DISCUSSION

KEY MESSAGE 1: Dry conditions and seasonable temperatures expected this week. Colder conditions this weekend.

Tonight: High pressure will prevail again tonight with a modest northwest flow aloft. The boundary layer is poised to decouple quickly this evening once insolation is lost and a weak sea breeze along the coastal corridor breaks down. This will result in a calm to light/variable wind regime. These winds combined with mostly clear skies will promote moderate to strong radiational cooling with low expected to drop into the lower-mid 40s inland to the upper 50s at the beaches. The 08/13z NBM lows looked reasonable overall (somewhat unusual given its typical warm bias in radiational regimes), but some output from the RRFS, H3R and RAP was incorporated to better capture the large temperature gradient along the coastal counties and to resolve the more typical mesoscale influences across the Francis Marion National Forest, the Santee-Cooper lakes and the open areas of Fort Stewart.

There is a risk for some fog early Monday morning, but model 1000 hPa condensation pressure deficits are not ideal. This suggests any fog that form will likely be shallow in nature with vsbys varying greatly over short distances. The risk for more substantial fog looks greatest near the Altamaha River where some slightly deeper fog layers could form resulting in at least some locally dense fog at times. The best juxtaposition of REFS and NBM probabilities for vsby <1 mile are only running about 30-50% over parts of Tattnall, Long, McIntosh, Liberty and Bryan Counties. The overall risk for widespread dense fog looks pretty low at this point, but this will be closely monitored.

Monday through Wednesday: Surface High pressure will prevail across the Southeast U.S., bringing dry conditions. High temperatures all three days should range from the mid 70s to upper 70s, except cooler at the beaches. These values are a few degrees above normal. The combination of light to calm winds and mostly clear skies for the first half of Monday night should lead to decent radiational cooling. Lows should dip to around 40 degrees far inland, and the 50s at/near the beaches. An increase in clouds should warm up low temperatures a few degrees Tuesday night, and then again Wednesday night.

KEY MESSAGE 2: Freezing temperatures are possible across far inland areas Friday night, followed by a potential widespread freeze Saturday night.

A fast moving cold front will zoom through our region on Thursday. This may bring a brief period of light showers, mainly to inland locations. It's still too early to determine the exact QPF amounts, but the models point towards very little QPF. What the models do show is strong cold air advection behind the front, which will lead to breezy conditions and below normal temperatures. Highs on Friday may struggle to reach the mid 60s. But more noteworthy will be the low temperatures. Freezing temperatures are possible across our far inland locations Friday night. Saturday, highs may not even reach the 60 degree mark. That'll be reflected with the coldest night so far this season. There is the potential for a widespread freeze Saturday night, except near the coast.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Generally prevailing VFR through the 00Z TAF period at KCHS/KJZI/KSAV. There is a risk for shallow ground fog at all terminals late tonight/early Monday morning, with the greatest risk for impacts at KSAV. MIFG was highlighted just before daybreak with a TEMPO for MVFR vsbys at KSAV 10-12z.

Extended Aviation Outlook: VFR during the daytime, with visibility restrictions possible during the late overnight into early morning hours on both Tuesday and Wednesday. Speeds will remain less than 10 kt with seas 2-4 ft.

MARINE

Through Tonight: Tranquil conditions will prevail. Northeast winds will gradually become variable for a time tonight, then turn west to northwest as daybreak approaches. Speeds will remain less than 10 kt with seas 2-4 ft.

Monday through Friday: Surface High pressure will prevail across the Southeast U.S. the first half of this week, bringing a light to perhaps gentle breeze. Seas will be 2-3 ft within 20 nm and 3-4 ft for the 20-60 nm waters. Winds increase Thursday ahead of an approaching cold front, becoming gusty. Likewise, wind- driven seas will build. Small Craft Advisories will likely be needed for our waters.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.