textproduct: NWS Wilmington

WHAT HAS CHANGED

Aviation discussion updated for 06Z TAF issuance.

KEY MESSAGES

1) Summerlike Bermuda high pressure will maintain southerly winds and unseasonably warm weather throughout the week.

2) The next cold front may arrive late Sunday accompanied by an increased chance of showers or t-storms.

DISCUSSION

KEY MESSAGE 1: Summerlike Bermuda high pressure will maintain southerly winds and unseasonably warm weather throughout the week.

An expanding upper level ridge off the Southeast coastline this week will support Bermuda High Pressure at the surface in a pattern that looks straight out of July. True, parameters like surface and 850 mb temperatures and 500 mb heights aren't at mid summer levels, but the overall pattern is very summerlike.

Forecast 500 mb heights near 5850 meters Thursday and Friday are above the 90th percentile for this time of year for both the Charleston and Morehead City upper air sites. A subsidence inversion between 7500-12000 feet AGL should cap off surface- based convection beginning Wednesday, meaning any isolated showers that can form later this week should remain shallow with little to no potential for lightning.

Inland forecast highs are in the 80-85 range each day through Sunday. Coastal areas should remain ~5 degrees cooler due to onshore synoptic flow supplemented by the daily seabreeze circulation each afternoon. This is still 6-12 degrees above normal for this time of year.

KEY MESSAGE 2: The next cold front may arrive late Sunday accompanied by an increased chance of showers or t-storms.

Latest guidance continues to align with a cold fropa late Sunday. An upper low centered near the Great Lakes on Sunday should swing an upper trough across the Carolinas Sunday into Sunday night, potentially advecting a swath of Gulf moisture overhead and breaking down the ridge aloft enough to allow convection to develop along and ahead of the front. Current forecasts have 40 percent rain chances developing Sunday into Sunday night as this front approaches.

It's too early to get a clear handle on whether any severe weather potential will exist with this front. Forecast modest mid and upper wind speeds (strongest on the Canadian, weakest on the GFS) currently don't argue for this being a good severe weather setup, but these details will become more clear in the days ahead.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

VFR is expected to prevail through the period, although brief MVFR vis cannot be ruled out at KLBT or KFLO between 10-12Z if winds can become calm for long enough. A respectable southwesterly LLJ of 20- 25 kts inland and up to 15-20 kts nearer to the coast is forecast mainly between 1-3kft. This should keep light winds going all night with brief periods of calm, precluding any widespread fog threat. Otherwise, a layer of shallow altocumulus is anticipated between 6- 8kft, resulting in SCT to BKN cigs away from the coast from late morning through the afternoon. These clouds will dissipate late in the day, leaving a mostly clear sky late in the period.

Extended Forecast... Mainly VFR conditions are expected, although the potential exists for early morning fog/stratus Wed/Thu/Fri mainly across the inland terminals. Sea fog may become an issue beginning for the coastal terminals toward the end of the week and weekend.

MARINE

Through Tonight... Offshore high pressure will maintain steady south winds between 5-15 kts over the waters through the period. Nearshore enhancement due to the sea breeze is possible, along with slightly backed winds towards SSE. Seas are expected to subside slightly from 2-4 ft to 2-3 ft by early afternoon, mainly driven by a southeasterly swell with a period around 7 sec.

Wednesday through Saturday... Sub-SCA conditions continue for the second half of the week. With Bermuda high pressure locked in place well offshore and low pressure systems staying off to the north and west, winds will average out of the S to SE at only 5-15 kt, with daily enhancement nearshore from the sea breeze. Seas steady at 2-4 ft, mainly consisting of 7-9 second SE waves.

ILM WATCHES/WARNINGS/ADVISORIES

NC...None. SC...None. MARINE...None.