textproduct: Newport/Morehead City

WHAT HAS CHANGED

The Flood Watch has been cancelled early.

KEY MESSAGES

1) Increased risk of thunderstorms with heavy rainfall continues today

2) Drier air and a reduced risk of thunderstorms Sunday and Monday, especially inland. A thunderstorm risk may linger along the coast.

DISCUSSION

KEY MESSAGE 1...A mid-level shortwave will lift slowly northeast along the coast of the Carolinas this morning, then shift away from the coast this afternoon. An attendant area of low pressure will also lift northeast along the coast while pulling a warm front north with it. The SFC low and warm front are expected to provide an area of enhanced low-level convergence along their trek up the coast. How close to the coast the low travels, and how much instability can be realized, will be important factors for which areas see the heaviest rainfall rates today. Given how convectively overturned the airmass is from yesterday, it may be that the instability gradient will reside right along the immediate coast, which would favor areas from coastal Onslow northeast through the OBX for the heaviest rainfall today. It's also possible that the instability gradient remains just offshore, keeping the higher rainfall rates offshore as well. Regardless, the heaviest rainfall axis should reside east of where the heaviest rainfall axis was yesterday, and east of where the Flood Watch originally covered. In light of that, the Flood Watch has been cancelled, and a watch is not currently anticipated for the coastal areas today due to 1) sandy soils which can be harder to flood, and 2) uncertainty regarding whether or not the higher instability will develop along the coast or offshore.

Further inland, showers and scattered thunderstorms remain possible, but rainfall rates should be lower than yesterday due to less instability. However, some instances of minor poor drainage flooding may still occur.

KEY MESSAGE 2...An anomalously strong upper level trough is forecast to translate east from the Great Lakes to the Northeast U.S. Sunday and Monday. Meanwhile, an associated strong cold front is forecast to push east across the Mid-Atlantic and Carolinas with much drier air in tow behind it. Normally this would spell a reduced risk of thunderstorms for ENC, and for most areas it probably will. However, recent guidance has started to trend slower with the front's eastward progression as the upper level forcing shifts NE away from the region, leaving the tail end of the front to potentially stall near the coast of the Carolinas. There appears to be 2 possible scenarios at this point, each of which is outlined below.

SCENARIO 1: The front clears the coast of ENC. This scenario favors a reduced risk of convection areawide along with slightly below normal overnight lows and lower humidity. This scenario was previously favored, but has recently lost some model support.

SCENARIO 2: The front makes it to the coast, but then stalls. In this scenario, dry conditions are favored inland, but with a risk of thunderstorms lingering along the coast. Interestingly, this scenario offers the potential for a sneaky strong to severe thunderstorm risk as drier mid-level air becomes more supportive of damaging downbursts. Lift and shear could also be enhanced as the area would remain in the entrance region of a strong upper jet. Lift could also be enhanced if a surface low rides up along the stalled front. Machine learning guidance do not show much of a signal for strong to severe convection, while the ECMWF's EFI guidance does show a decent signal. This scenario has been gaining some support in recent runs.

For now, much of ENC is likely to remain dry Sunday and Monday, but for coastal areas, the thunderstorm risk is something worth keeping an eye on.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

Forecast confidence is low to moderate over the next 24 hours.

An area of low pressure will lift northeast along the coast of North Carolina this morning, then move away from the area by this afternoon. Inland of the low, the TAF sites will have to contend with periods of IFR/MVFR, with brief bouts of LIFR conditions possible this morning. Eventually, CIGs should rise to high end MVFR or VFR levels. Low CIGs or BR/FG may redevelop tonight, but confidence in this is low.

A risk of TSRA will accompany today's low as well, although the greatest risk looks to be focused along, and just inland of, the coast. TSRA will be capable of LIFR/IFR VIS and gusty winds to 40kt.

Outlook: A stronger cold front is forecast to reach the area on Sunday, but guidance now suggests it may stall along the coast through Monday. Should this occur, the TSRA risk would linger along the coast longer than previously forecast. However, even in that scenario, the risk may remain just east of the TAF sites.

MARINE

Low pressure will lift northeast along the coast of the Carolinas this morning, then shift away from the area this afternoon. There will be an increased risk of thunderstorms along this low, especially for the central and southern waters. The inland rivers and sound and the northern coastal waters will still have a risk of thunderstorms today, but the risk looks a bit lower compared to yesterday. The low is not particularly strong, therefore winds should remain below 25kt for most waters. The exception is the outer coastal waters where occasional gusts to 25kt can be expected where the gradient will be the strongest. For the nearshore coastal waters, seas of 2-3ft are expected through tonight. For the outer coastal waters, seas of 3-5ft are expected.

Outlook: A strong cold front will move into the ENC waters on Sunday, but may stall over the area through Monday. Where the front stalls is where the thunderstorm risk will be the highest through Monday. Strong winds of 40kt+ and waterspouts will be possible with the strongest storms. Eventually the front is forecast to move away from the area with winds laying down. Seas of 2-4ft are expected through Monday, but then are expected to lay down to around 2ft by Tuesday.

MHX WATCHES/WARNINGS/ADVISORIES

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