Marine Weather and Tide Forecast for Calabash, NC

KEY MESSAGES
1) Inland portions of the eastern Carolinas should see their longest heat wave of the year so far with 90+ degree heat expected to continue through Thursday.

2) Rain chances should increase, especially inland, beginning Thursday as a front temporarily stalls in the Carolinas.

DISCUSSION
KEY MESSAGE 1...Inland portions of the eastern Carolinas should see their longest heat wave of the year so far with 90+ degree heat expected to continue through Thursday.

An upper high will shift into the Atlantic and leave an axis of higher heights from the Gulf into the central Atlantic, and this is responsible for the sustained period of hot inland temperatures, which should last through Thursday. Sinking air below the upper ridge will create a deep warm, dry layer in the middle troposphere, supporting abnormally warm surface temperatures. Models have maintained their 850 mb temp forecasts of +16C to 18C (at or above the 90th percentile climatological values for this time of year), which increases confidence in our forecast of 90+ degree heat continuing through Thursday for locations away from the daily cooling influences of the sea breeze.

Our forecast is for an additional three days (Tuesday through Thursday) of 90+ degree heat inland. Since Florence and Lumberton highs reached 90 degrees on Sunday, a five day streak would eclipse this year's earlier streak of four days of 90 degree temps recorded from April 15-18 in both Florence and Lumberton. Coastal portions of the Carolinas should remain significantly cooler than inland due to sustained south winds dragging air across nearshore water still near 70 degrees.

The upper ridge will become increasingly narrow with time as an upper low strengthens across the northern Bahamas Tuesday into Thursday. This feature looks a lot like an early season TUTT low, but any enhanced convection or other sensible weather impacts should remain far to our south. The arrival of a surface cold front Thursday afternoon should end this heat wave with temperatures returning toward normal for Friday. However, the front is expected to stall and lift back north, with troughing to the west and a ridge centered over the Atlantic supporting more of a daily pop-up convection pattern over the weekend. Thus, high temps will depend on the extent of cloud cover and precip that develops.

KEY MESSAGE 2...Rain chances should increase, especially inland, beginning Thursday as a front temporarily stalls in the Carolinas.

Dry weather will come to an end as a front shifts in from the north on Thursday. There's reasonable uncertainty on placement of highest POPs day to day as we deal with a stalled front in or near the area and the daily sea breeze. The front should lift north of the area into the weekend but the warm, humid air mass will continue to support at least daily pop-up shower and storm chances through the end of the period.

With respect to the lowering of precip chances late in the week and over the weekend, NBM-based and GEFS/ECME precip probabilities appear overdone given the expected pattern with a ridge over the Atlantic and troughing well west of the area.
While the incoming front could bring enhanced precip coverage due to surface convergence along the boundary paired with a warm and humid troposphere, little in the way of upper support is depicted amongst the global models, lending lower confidence to a widespread coverage of precip than what would be expected with 70-80% PoPs. In addition, GFS MOS and ECME MOS output both support lower probabilities for precip generally at or below 50%. Thus, PoPs were lowered until confidence increases in when and where a period of greater precip coverage can be expected.

AVIATION /18Z MONDAY THROUGH SATURDAY/
We have high confidence in VFR conditions continuing through 06z Tuesday. Light southerly winds could increase to 10-15 knots along the coast with the seabreeze through 00z.

After 06z Tuesday, high humidity in the lowest 1000-1500 feet of the atmosphere and clear skies aloft should set the stage for the development of fog and/or low ceilings late tonight. There is some raw model and statistical guidance suggesting fog could become dense in spots, but for now we're forecasting MVFR visibility and scattered low clouds developing around 08z and persisting through 12z Tuesday morning. Once daytime heating clears up surface visibility, dry air aloft should result in fewer low clouds lingering compared to what we saw this morning.

Extended Forecast...Areas of low clouds and fog are possible Wednesday through Saturday mornings, generally in the 08z-12z timeframe. Confidence is moderate. Shower and thunderstorm chances will increase across the entire area Friday into Saturday as a front stalls across the Carolinas.

MARINE
Through Tuesday...Bermuda high pressure ridging westward across South Carolina will maintain dry weather and a light southerly wind across the area. Superimposed on this synoptic wind will be a landbreeze/seabreeze pattern that should lead to localized stronger wind speeds (10-15 kt) nearshore during the afternoons and evenings.
Seas should average 2 feet across the coastal waters (2-3 feet for the waters out to 60 miles) mainly in an 8-second southeast swell.

Tuesday night through Saturday... Offshore high pressure will maintain control through midweek until a cold front approaches from the north. This front looks to stall near or over the waters before lifting back northward by late Friday. Generally south winds can be expected until the front draws near, with a period of east or even northeast winds possible near the coast if the front can push offshore; otherwise, expect southeast winds ahead of the front.
Speeds are expected to stay between 5-15 kts, with enhanced nearshore gustiness due to the sea breeze likely each day. Seas are expected to hold in the 2-3 ft range in the 0-20nmi zone and 3-4 ft in the 20-60nmi zone through the period, mainly driven by persistent southeasterly swells with a period of 8-9 sec.

ILM WATCHES/WARNINGS/ADVISORIES
NC...Coastal Flood Advisory from 10 PM this evening to 2 AM EDT Tuesday for NCZ107.
SC...Coastal Flood Advisory from 8 PM to 11 PM EDT this evening for SCZ054-056.
MARINE...None.