textproduct: Charleston

WHAT HAS CHANGED

Key Messages 1 and 2 have been updated to reflect current trends. The aviation section has been updated for the 18z TAFs. Marine section has been updated to address gales.

KEY MESSAGES

- 1) Windy conditions through sunset.

- 2) Cold weather with sub-freezing temperatures returns tonight and lingers into mid-week.

DISCUSSION

KEY MESSAGE 1: Windy conditions through sunset.

The cold front is now well offshore. Post-frontal cold air advection and the associated isallobaric response will continue to strengthen through the afternoon. This will result in strong vertical mixing with winds expected to reach 20-30 mph with gusts as high as 40-45 mph at times. Wind gusts in excess of 40 mph have already been observed across much of Southeast Georgia, including a 44 mph gust at the Savannah International Airport around 1130 AM. A Wind Advisory remains in effect, but was extended slightly until 7 PM. Winds should diminish below advisory levels after sunset, although elevated winds will remain through the night. Winds of this magnitude are capable of downing small trees and large limbs. Driving could also be difficult, especially for high profile vehicles.

KEY MESSAGE 2: Cold weather with sub-freezing temperatures returns tonight and lingers into mid-week.

A modified arctic airmass will filter into the area tonight as sprawling high pressure over centered south-central Canada builds south. The pressure gradient between the building high and the departing nor'easter will keep winds up overnight. As temperatures fall into the upper 20s/lower 30s just before daybreak Monday, the lingering elevated winds will help drive wind chills into the mid-upper teens inland to within a degree or two of 20 at the coast. A Cold Weather Advisory has been issued from midnight to 8 AM Monday for all of the South Carolina Lowcountry and Southeast Georgia. It is a bit marginal for the coastal zones where it seems unlikely everywhere will see wind chills bottom out at 20 degrees, but an advisory seemed warranted given the near record to record warmth that has been experienced recently.

It will be considerable colder for Monday with highs only warming into the upper 40s/near 50. A lingering northwest wind will make it feel closer to the upper 30s/lower 40s, which is a big change from the past few days. The coldest night of the upcoming week will occur Monday night as the center of the high draws closer. While full boundary layer boundary layer seems unlikely at this point, winds should go fairly light, especially inland. Lows will bottom out in the lower-mid 20s inland to the lower-mid 30s at the beaches. A few spots could approach Cold Weather Advisory criteria inland, but it looks to remain fairly isolated/localized. The need for an advisory for these areas will be reassessed on Monday.

AVIATION /15Z SUNDAY THROUGH THURSDAY/

22/18z TAF Discussion: KCHS/KJZI/KSAV: VFR through 23/18z. Gusty winds will persist through the period.

Extended Aviation Outlook: An approaching front could bring flight restrictions late Friday.

MARINE

Through Monday: Hazardous marine conditions with gale conditions will impact all waters tonight. Frequent gusts of 35-45 kt gales can be expected with sustained winds 20-30 kt within 20 NM and 30-35 kt over the Georgia offshore waters. Gale Warnings are in place through tonight. Winds in the Charleston Harbor are expected to drop below gale force by early evening, so the Gale Warning there will be replaced with a Small Craft Advisory. There will be a large gradient in wave heights, ranging from 2-3 ft near the immediate coast to as high as 10 ft over the Georgia offshore waters. Mariners are urged to remain in port.

Tuesday through Thursday: High pressure will pass south of the waters on Tuesday, bringing lower winds and seas. As the High passes offshore Tuesday night into Wednesday, there should be a surge of winds, which may prompt Small Craft Advisories for portions of our waters. Conditions improve Wednesday night, only to deteriorate again on Thursday, which may prompt additional Small Craft Advisories for all of our waters.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Wind Advisory until 7 PM EST this evening for GAZ087-088- 099>101-114>119-137>141. SC...Wind Advisory until 7 PM EST this evening for SCZ040-042>045- 047>052. MARINE...Gale Warning until 7 PM EST this evening for AMZ330. Gale Warning until 8 AM EST Monday for AMZ350-352-354. Gale Warning until 10 AM EST Monday for AMZ374.