Marine Weather and Tide Forecast for Sea Breeze, NC

UPDATE
Aviation discussion updated below for 18z TAFs. Continued to make some adjustments to dewpoints, to account for readings in the low to mid 30s. As sea breeze develops and winds shift to a more onshore easterly direction this afternoon, expect higher dewpoint air to spread inland, especially over SC which is farther away from center of high and will get better easterly component to the flow.

NEAR TERM /THROUGH TONIGHT/
A 500 mb ridge axis extending northward from a high across the western Gulf will draw closer to the Carolinas tonight. Northwest flow ahead of this incoming ridge contains a shallow layer of moisture between 500-400 mb, approximately 20kft aloft, associated with an extensive canopy of clouds from east TN almost to Cape Fear.
These clouds should gradually fade with time and mostly sunny conditions are expected later today.

Surface high pressure will move eastward across Virginia, maintaining a northeasterly wind across the area until early afternoon. Diurnal mixing up into some very dry air aloft may crash dewpoints into the 30s for areas of north of Myrtle Beach with relative humidity likely falling below 30 percent. Wind directions gradually veering more easterly with time will lead to expanding maritime influence and moderating humidity late in the afternoon.
Forecast highs range from the mid 70s on the beaches to around 80 across Florence and Hartsville, very near MOS consensus. Clear skies and light winds tonight should allow temps to fall through the 50s, landing near the lower end of MOS consensus.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
Mid-level ridging will dominate the short term period with dry weather and a warming trend overall. Surface high pressure will shift to a position between the coast of the Carolinas and Bermuda on Tuesday, veering winds from southeasterly to southerly on Tuesday, which will then persist through Wednesday night. South winds and associated warm advection will bring increasingly warm temps through midweek from the upper 70s to low 80s for highs on Tuesday (<5F above normal) to the mid-upper 80s inland on Wednesday (generally 5-10F above normal). Low temps will rise from around 60F on Tuesday night to the low 60s on Wednesday night.

LONG TERM /THURSDAY THROUGH MONDAY/
The weather becomes more interesting late in the week as active weather along a cold front approaches from the west. However, Thursday looks to be another dry day as mid-level subsidence and dry air hold for one more day, although plenty of high clouds should be streaming overhead. High temps should once again reach 5-10F above normal into the mid-upper 80s inland and low-mid 80s near the coast as offshore high pressure maintains southerly flow and a healthy supply of warm, moist low-level air.

After a mild start with lows in the middle 60s, Friday is shaping up to be convectively active as mid-level lapse rates steepen into the 6-6.5C/km range, allowing for moderate instability to develop (SBCAPE in the 1000-2000 J/kg range) as daytime heating pushes surface temps into the mid-upper 80s once again. Southwesterly winds over land and south winds behind the sea breeze should yield enough convergence to get isolated to scattered storms developing in the afternoon, especially as mid-level height falls continue ahead of an approaching trough.

A surface cold front is progged to arrive by late Friday night with additional showers and thunderstorms possible, but the coverage is questionable due to the majority of the synoptic forcing for ascent passing to our north. In addition, due to the nighttime timing of the front, earlier instability will wane considerably and reduce the risk of thunderstorms overnight.
PoPs persist into Saturday as uncertainty remains around the timing of when the dry air filters in. Thus, confidence is low in whether Saturday will be mostly dry or have additional precip concerns, and this will influence high temps as well.

By Sunday, subsidence and dry air should be solidly in place aloft with high pressure and cool north winds knocking temperatures back to near or just below normal.

AVIATION /18Z MONDAY THROUGH SATURDAY/
VFR conditions should continue through the TAF period. Easterly winds less than 10 kts with gusts to 15 kts this afternoon at coastal terminals, will drop off 00-02z becoming near calm.
Very low probability of shallow ground fog creating visibility constraints at KCRE between 06z and 12z. Winds will pick up slightly between 14-16z out of the SE to S but should remain less than 10 kts. Expect mainly clear skies with few to sct cu into Tues aftn.

Extended Outlook...Generally VFR. MVFR/IFR is possible Wednesday morning and Thursday morning in ground fog.

MARINE
Through Tonight...
Surface high pressure centered over Virginia this morning should move east and off the Mid Atlantic coast. This will tend to slowly veer our wind directions from northeasterly this morning to southeasterly tonight, but with no real increase in synoptic wind speed expected. Winds should remain around 10 knots, except 10-15 knots south of Myrtle Beach with seas in the 2-3 foot range through tonight.

Tuesday through Friday...
High pressure will slide to a position in between the Carolinas and Bermuda on Tuesday, leading to southeasterly winds early on Tuesday veering to southerly by late in the day. South- southwesterly winds then dominate from Wednesday onward as the high remains firmly in place offshore. As a cold front approaches from the west late in the week, expect the pressure gradient to tighten and lead to increasing winds on Thursday and especially Friday, although gusts should stay just shy of SCA criteria. Otherwise, Friday also looks to feature a more active sea breeze, with thunderstorms possible near the coast.

Given the benign conditions through Thursday, seas hold in the 2-3 ft range, driven primarily by ESErly swells with a period of 8 sec, which is then topped by diurnally-driven wind waves out of the south. This changes on Friday as the swell component weakens in favor of strengthening southerly wind waves reaching 3-4 ft.

TIDES/COASTAL FLOODING
Large tidal ranges associated with this month's New Moon should create another night of minor coastal flooding. Where confidence in impacts is largest, I'm going to go ahead and raise a Coastal Flood Advisory for the upper South Carolina coast encompassing the beaches of Horry and Georgetown counties. Beaches across southeastern North Carolina including locations along the tidal Cape Fear River could experience minor flooding as well but current forecasts aren't a lock for impacts just yet.

ILM WATCHES/WARNINGS/ADVISORIES
NC...None.
SC...Coastal Flood Advisory from 7 PM to 10 PM EDT this evening for SCZ054-056.
MARINE...None.