textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Below-normal rain chances are expected through the weekend. - 2) Temperatures are expected to rise late this week and through the weekend, likely approaching triple digits this weekend. Heat Advisories could be needed.

DISCUSSION

KEY MESSAGE 1: Below-normal rain chances are expected through the weekend.

Rest of today and tonight: Surface observations and satellite imagery suggest that the front sits somewhere just north of the Savannah River entrance and extends inland across southeast GA. We are actually seeing some shower development along the boundary offshore where a waterspout was reported offshore of Hilton Head just after 10 am. Drier air has pushed southward across the forecast area and precipitable water values are uncharacteristically low, generally 1-1.25" as we approach the early afternoon. The hi-res model consensus and the 24/12z HREF continue to suggest that if any diurnal convection develops today it will be across a limited area that includes Beaufort, Jasper, Chatham, Effingham, Bryan, and Liberty counties. But, there are considerable obstacles to overcome to get development including copious dry air aloft and capping centered around 600-700 mb. Anything that does develop should remain relatively weak and short-lived. Any chance of development is expected to come to an end this evening as surface heating wanes and the overnight looks to be dry.

For the latter part of the week and into the weekend, the surface pattern is expected to increasingly become dominated by subtropical high pressure. Model consensus is for at best scattered thunderstorm coverage, with the best chances appearing to be Friday, and then perhaps Sunday and Monday. Overall, there aren't any significant features to focus or drive initiation, so development will be dependent on surface heating and perhaps the sea breeze. Also, there does not appear to be any notable severe threat at this time.

KEY MESSAGE 2: Temperatures are expected to rise late this week and through the weekend, likely approaching triple digits this weekend. Heat Advisories could be needed.

The main story for the latter part of the week and through the weekend will be well above normal temperatures. Low to mid 90s are forecast to return by Thursday, mid to upper 90s by Saturday, and near 100 for Sunday into Monday. Dewpoints are also expected to be on the rise, especially from Friday onward, yielding increasing heat index values as well. The probability of heat index values into the 105-110 degree range will rise notably for Saturday through Monday, especially along the coast where the highest dewpoints are anticipated. Confidence in the magnitude of the heat threat remains relatively low this far out, but Heat Advisories could eventually be needed for at least portions of the area.

Additionally, low temperatures will be on the rise each night and we could approach daily record high minimums. See the Climate section below for additional details.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

VFR conditions are expected to prevail at KCHS, KJZI, and KSAV through 18z Thursday. For this afternoon, the best chance of seeing a shower or thunderstorm remains at KSAV. Overall chances are still relatively low as coverage is expected to be isolated at best, but the main time period of concern would be between 2-5pm. Overnight, there are some hints that shallow ground fog could develop, but no significant visibility reductions are anticipated is any does form.

Extended Aviation Outlook: VFR conditions are expected to prevail.

MARINE

Through tonight: Northeast winds this afternoon will gradually turn more east and southeast into the evening with speeds mostly topping out up to 15-20 knots. Flow will weaken considerably overnight, becoming 5 knots or less late. Seas should mostly average 2-3 feet.

Thursday through Monday: A pretty typical pattern is expected through the weekend and into early next week. Winds will generally be south to southwest, with some modest surging into the 15-20 knot range at times. Winds will increase along the land/sea interface each afternoon and evening with the development of the sea breeze. We could see a period of gusts up to around 25 knots Friday evening through Saturday evening across the Charleston County waters, and a marginal Small Craft Advisory could be needed.

CLIMATE

Record High Temperatures:

June 28: KCHS: 99/1998 KCXM: 100/1959 KSAV: 100/1998

Record High Minimum Temperatures:

June 27: KCHS: 77/2015 KSAV: 79/1952

June 28: KCHS: 78/2013 KCXM: 81/1998 KSAV: 80/1880

June 29: KCHS: 79/1977 KCXM: 83/1998 KSAV: 80/1885

CHS WATCHES/WARNINGS/ADVISORIES

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