textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 19/12z TAFs.

KEY MESSAGES

- 1) Rain chances likely to increase late in the week, though no hazardous weather is anticipated at this time.

DISCUSSION

KEY MESSAGE 1: Rain chances likely to increase late in the week, though no hazardous weather is anticipated at this time.

Atlantic high pressure centered well offshore will maintain its influence on the region today. Subsidence will begin to increase aloft later today as the pronounced Tropical Upper Tropospheric Trough (TUTT) positioned near 29N/73W prior to daybreak draws closer to the Southeast U.S. coast and continues to slides west beneath the subtropical anticyclone centered well east of Cape Hatteras. This coupled with low 850 hPa theta-e will keep rain- free conditions in place even as a pure sea breeze circulation moves steadily inland through the afternoon and evening. Highs will continue to run a few degrees above normal with highs poised to peak in the lower 90s inland to the mid-upper 70s at the beaches. Similar to the past few days, the boundary layer will likely not completely decouple until well after midnight as the sea breeze moves into the Southern Midlands, CSRA and east-central Georgia. Light winds and mostly clear skies will support modest radiational cooling with lows ranging from the mid 60s inland to the lower 70s at the beaches. Another round of shallow ground fog appear likely away from the beaches, but impacts should be minimal with models show rather high 1000 hPa condensation pressure deficits.

Sfc high pressure holds tight across the region through Wednesday, allowing quiet conditions to prevail. As noted in days past, should see the upper level pattern shift as we head into the latter half of the week, when a shortwave trough deepens across the northern Plains. Meanwhile, at the sfc, will see a cold front extending from Maine to Texas dive southeastward ahead of this feature, causing rain chances to return to the forecast.

Unfortunately, model guidance and certainty remain rather poor at this time, keeping overall confidence in rainfall occurrence and timing low. Latest trends would favor a stronger ridge over the Atlantic, resulting in the aforementioned front and forcing staying further west and north of our area. As such, this scenario would entail seeing less precipitation across our area than previously forecasted. In fact, current ensemble probabilities for seeing rainfall accumulations greater than one inch through Saturday have now dropped to less than 25% (with the greatest threat still inland) - whereas yesterday probabilities ranged from 20-60%. Certainly something to keep an eye on, as model runs could still shift in the coming days. Otherwise, expect the severe potential with any shower/storm to remain low, given the lack of forcing and moisture in place.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

19/12z TAF Discussion: KCHS/KJZI/KSAV: Shallow ground fog at all three terminals will quickly dissipate at sunrise. VFR for the period. Gusty winds will occur with the passage of the sea breeze this afternoon. Shallow ground fog will be possible again at all terminals early Wednesday morning.

Extended Aviation Outlook: There are no high confidence concerns.

MARINE

Through Tonight: Quiet conditions will persist with the region positioned along the western flanks of Atlantic high pressure centered well offshore. East/southeast winds will prevail with speeds less than 15 kt, although some local enhancement along the land/sea interface and Charleston Harbor will likely occur with the sea breeze. Seas will average 2-4 ft.

Wednesday through Friday: No marine concerns are expected. High pressure to the east will drive onshore east-southeasterly flow each day, with wind speeds mostly topping out in the 10-15 knot range. Each afternoon and evening there could be some local enhancement along the land/sea interface with the diurnal sea breeze. Seas should average 2-4 feet through the period.

Rip Currents: Influences from the new moon cycle combined with persistent onshore flow will produce an elevated risk of rip currents. A moderate risk for rip currents is in place for all beaches today.

CHS WATCHES/WARNINGS/ADVISORIES

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