textproduct: Charleston

WHAT HAS CHANGED

A new Key Message for smoke generated by the Horse Island Wildfire was introduced. The Aviation and Marine sections were also updated.

KEY MESSAGES

- 1) Smoke from the Horse Island Wildfire will impact northeast Berkeley County tonight into Monday.

- 2) Hot and humid conditions are expected across the area into midweek. Heat Advisories could be needed.

- 3) A shift in the synoptic pattern will likely bring higher precipitation chances towards the end of the week.

DISCUSSION

KEY MESSAGE 1: Smoke from the Horse Island Wildfire will impact northeast Berkeley County tonight into Monday.

A Dense Smoke Advisory has been requested by the U.S. Forest Service for northeast portions of Berkeley County in response to the Horse Island Wildfire. Smoke in the vicinity of the fire is significant and conditions will deteriorate overnight as the nocturnal inversion develops. The latest Hysplit output shows the worst of the smoke will remain across northeast Berkeley County and extending across the Santee River into a small area of southwest Georgetown County. Visibilities may drop below 1/4 mile at times overnight, especially along parts of Highway 45. Road closures are possible. Smoke will likely remain an issue into Monday although visibilities should improve some by mid- morning as dispersion increases and mixing heights rise.

KEY MESSAGE 2: Hot and humid conditions are expected across the area into midweek. Heat Advisories could be needed. Very little change in the forecast is expect the next couple of days as the heat and humidity lingers through Wednesday. The overall players remain the same across the area with deep upper troughing across the Northeast, high pressure to our east over the Atlantic and a tropical depression over the northern Gulf. Monday and Tuesday, will see highs topping out in the low to mid 90s and dewpoints able to mix out into the low 70s. This should be enough to keep heat indices in the 100 to 105 range and while this is still hot, this is more in line with typical summertime conditions for the area. The bigger questions come on Wednesday as dewpoints should gradually increase as better moisture arrives. This will be aided by the disturbance in the Gulf as it slowly tracks westward. The usual trouble areas behind the seabreeze could start to approach advisory criteria come Tuesday into Wednesday as dewpoints climb into the upper 70s to near 80 resulting in heat indices of around 108 to 110. This could require Heat Advisories across portions of the area.

KEY MESSAGE 3: A shift in the synoptic pattern will likely bring higher precipitation chances towards the end of the week.

Monday the region will remain positioned between low pressure in the Northern Gulf (TD2) and high pressure over the Western Atlantic. This pattern will persist into Tuesday, with TD2 slowly shifting westward into Wednesday. As the low pressure shifts westward a mid level trough will set up over the eastern CONUS. At the surface a cold front will approach the region Wednesday, likely stalling in the vicinity of the forecast area into the end of the week. This stalled front is likely to bring increased precipitation chances to the region. The Weather Prediction Center has the entire forecast area outlooked in a Marginal Risk for Excessive Rainfall on Thursday, with a Slight Risk over northern Charleston and Berkeley Counties.

AVIATION /22Z SUNDAY THROUGH FRIDAY/

20/00Z Aviation Discussion: KCHS/KSAV/KJZI: VFR through 21/00z. The greatest risk for isolated showers/tstms Monday afternoon looks to setup west of the terminals.

Extended Aviation Outlook: Prevailing VFR through mid week. Chances of flight restrictions increase later this week with a greater coverage of showers/thunderstorms.

MARINE

Tonight: As the local waters remain situated between an inland trough and a subtropical high to the east, this will yield breezy southwesterly flow through late tonight. Elevated south to southwest winds will persist, ranging from 15-20 kt off the Charleston County coast to 10-15 kt with gusts to 20 kt off the Georgia coast. Seas will average 3-4 ft.

Monday through Thursday: The marine waters will remain positioned between high pressure to the east and low pressure in the Northern Gulf (TD2). Mid-week a front will approach the region, stalling in the vicinity of the marine waters late week. Small Craft Advisories could be needed for this period, especially in the Charleston nearshore waters and the Charleston Harbor.

Rip Currents: A Moderate Risk of Rip Currents is in effect for our SE GA beaches Monday, given enhanced winds along the coastline and wave periods up to 6 seconds. A Moderate Risk returns to all area beaches on Tuesday as 6 second swell and enhanced SSW/SW winds develop along the entire coastline.

CLIMATE

Record High Minimum Temperatures:

July 19: KCHS: 79/1986 KCXM: 83/1986

July 20: KCHS: 79/2025 KCXM: 83/2000 KSAV: 79/1942

July 21: KCHS: 80/1986 KCXM: 83/1998

July 22: KCHS: 81/2011 KCXM: 83/2011

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...Dense Smoke Advisory until 10 AM EDT Monday for SCZ045. MARINE...None.