textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated for the 12Z TAF issuance.

KEY MESSAGES

- 1) There is a Lake Wind Advisory for Lake Moultrie through early this afternoon.

- 2) Dangerous fire weather conditions across our area today along with windy conditions at the coast. Red Flag Warnings are in effect along with Wind Advisories along the coast.

- 3) Dry with above normal temperatures next week.

DISCUSSION

KEY MESSAGE 1: There is a Lake Wind Advisory for Lake Moultrie through early this afternoon.

A dry cold front will quickly move southeast through our area early this morning, shifting far offshore at daybreak. Meanwhile, High pressure will build in from the northwest this morning. The combination of cold air advection and pressure rises will generate gusty north winds across Lake Moultrie this morning. Expect sustained winds 20-25 kts with gusts up to 30 kts this morning. A Lake Wind Advisory remains in effect for Lake Moultrie through 2 PM. Winds will ease this afternoon as cold air advection and pressure rises lessen. Additionally, waves should be 2-3 ft, especially across the center and southern portions of the lake.

KEY MESSAGE 2: Dangerous fire weather conditions across our area today along with windy conditions at the coast. Red Flag Warnings are in effect along with Wind Advisories along the coast.

Fire Weather: A dry cold front will quickly move southeast through our area early this morning, shifting far offshore at daybreak. Meanwhile, High pressure will build in from the northwest this morning. The center of this High will pass far to our north late today. The High will usher extremely dry air and gusty winds into our area, creating dangerous fire weather conditions. As is typical for this type of spring pattern, models don't adequately capture just how dry it will be. Therefore, we went much drier than guidance, going with the NBM10 for dew points. This matches up with minimum RH values in the HREF. Dew points will drop into the upper teens and 20s across most inland areas, but remain higher at/near the beaches. This will cause afternoon RH values to drop into the mid/upper teens very far inland, while generally being in the low/mid 20s across most of our area, with higher values at/near the beaches. These values will be reached late in the afternoon. Additionally, cold air advection and pressure rises from the High will lead to gusty northerly, then northeasterly winds. The strongest gusts will be in the morning, peaking in the 25-35 mph range across our SC counties and the 20-30 mph range across our GA counties. Winds should gradually ease into the afternoon, as cold air advection and pressure rises lessen. This is when RH values will really drop. So the strongest winds and lowest RH values won't line up perfectly. However, state, military, and federal land management agencies have reported some extreme fire behavior with controlled burns and a few wildfires over the past few days. This is on top of the ongoing drought. A Red Flag Warning is in effect for all of our counties, except coastal portions of Liberty and McIntosh Counties, until 8 PM. Humidity levels won't start to recover until this evening, with modest recoveries expected tonight. Winds will also be lower this evening and tonight.

Coastal Winds: The coastal winds will be heavily influenced by gales across the adjacent coastal waters. Winds of 20-30 mph with gusts 35- 40 mph will be possible with some areas along the beaches possibly gusting 40-45 mph at times. A Wind Advisory is in effect for all of our coastal zones until 2 PM. Winds of this magnitude can down trees and large branches. Isolated power outages could occur.

KEY MESSAGE 3: Dry with above normal temperatures next week.

A mainly dry/zonal pattern late weekend is expected to transition to a period of strong mid-lvl ridging along with persistent sfc high pressure across the Southeast United States, favoring a warming trend with mostly dry conditions heading into next week. Latest guidance supports high temperatures above normal by Monday, followed by even warmer conditions as the mid-lvl ridge axis is placed directly overhead. Afternoon highs could approach the low-mid 80s away from the coast (sea breeze influences) Tuesday through Friday.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

There could be a 2-3 hr window of MVFR cigs at CHS/JZI terminals this morning, which has been added as a TEMPO group at both sites from 12-15Z Saturday. Confidence remains too low to include restrictions at SAV at this time. The main issue will continue to be gusty wind conditions at CHS/JZI/SAV terminals for much of Saturday, with speeds generally gusting into the 25-30 kt between 12-21Z Saturday at CHS/JZI and 14-20Z Saturday at SAV. Wind speeds should begin to slowly decrease late Saturday afternoon into Saturday evening, dropping below 10kt at at TAF sites around 00Z Sunday. However, some gusty winds up to 15-20 kt could linger at JZI Saturday evening into early Sunday.

Extended Aviation Outlook: VFR through Tuesday next week. TEMPO flight restrictions possible at all terminals with showers and/or thunderstorms Wednesday, then again associated with an approaching front Thursday into Friday next week.

MARINE

Today and Tonight: A strong cold front will approach local waters from the north a few hours prior to daybreak, leading to conditions that quickly deteriorate as cold air advection promotes low-lvl mixing into 40-45 kt 1000 mb geostrophic wind fields. These conditions along with tightening pressure gradient will likely yield northeast wind gusts to gale force (35-40 kt) and building seas starting prior to daybreak and through much of the day Saturday. Gusts to around 35 kt are also anticipated near the Charleston Harbor entrance. As a result, Gale Warnings begin shortly across northern SC and Charleston Harbor waters with the passing front, followed by remaining waters just prior to daybreak. The risk for gales should end across the Charleston Harbor and nearshore waters by early Saturday afternoon and across the Georgia offshore waters by late Saturday evening. Seas will peak in the 5-9 ft range across nearshore waters and 9-12 ft over the Georgia offshore waters late Saturday night into Sunday. Small Craft Advisories will replace the Gale Warnings once they expire late Saturday afternoon and Saturday night, and could persist due to large seas for much of Sunday (nearshore) and into Monday (outer Georgia waters).

High Surf: Breaking wave heights could reach 5-6 ft along parts of the Georgia coast Saturday night into Sunday. A High Surf Advisory could be needed.

CHS WATCHES/WARNINGS/ADVISORIES

GA...Red Flag Warning until 8 PM EDT this evening for GAZ087-088- 099>101-114>119-137-138-140. Wind Advisory until 2 PM EDT this afternoon for GAZ117-119-139- 141. SC...Red Flag Warning until 8 PM EDT this evening for SCZ040- 042>045-047>052. Wind Advisory until 2 PM EDT this afternoon for SCZ048>051. Lake Wind Advisory until 2 PM EDT this afternoon for SCZ045. MARINE...Gale Warning until 2 PM EDT this afternoon for AMZ330. Gale Warning until 6 PM EDT this evening for AMZ350-352-354. Gale Warning until 2 AM EDT Sunday for AMZ374.