Key MESSAGE 1, A plume of anomalous, and deep, moisture will get pulled north through the Southeastern U.S. In advance of a cold front this weekend. The front will initially move through ENC on Saturday, then stall offshore before lifting back north on Sunday. This will occur as a weak area of low pressure rides NE along the front. As the low moves off the coast, it will drag the front back south through ENC later Sunday into Sunday night.
Modest heating of a moist boundary layer should allow moderate instability to build ahead of the front on Saturday, especially across our southern counties south of HWY 70. It's there where we expect the greatest coverage of showers and thunderstorms to be focused Saturday afternoon into Saturday evening. Guidance differ some on the progression of the front on Saturday, but with strong ridging centered offshore, it stands to reason that the progress of the front will be slowed, favoring a frontal passage during peak heating for our southern counties. Moderate instability plus 2"+ PWATs suggests a risk of high rainfall rates at times. Ensemble guidance suggests 0.50-1.50" of rain, on average, in this area. However, where convection is the most persistent, rainfall totals may reach as high as 2-3". This may support a risk of urban and poor drainage flooding. 3-hr flash flood guidance is 3-4" in this area, which suggests the risk of flash flooding is low based on the potential higher-end amounts being below FFG. It's worth watching, though, given such high moisture content.
On Sunday, guidance differ on how far north the front will get as it briefly lifts back north as a warm front. This doesn't appear to impact the ENC from a coverage standpoint. However, if the front were to lift further north, it could open up the potential for more instability to be available, which could support higher rainfall rates and amounts. This could also have an impact on temperatures. Regardless, increased low-mid level convergence interacting with a very moist airmass should lead to a widespread area of showers and isolated thunderstorms. For the area at large, the greatest coverage of showers and thunderstorms is expected on Sunday.
In total, 1-3" of rain appears likely for much of ENC over the weekend. The highest rainfall amounts should be across the southwestern counties of ENC where there will be the potential for heavy rain both Saturday and Sunday (compared to just Sunday for the northeastern counties of ENC).
The risk of severe thunderstorms continues to look low due to weak shear and weak mid-level lapse rates. However, perhaps a few water- loaded downdrafts of 30-40 mph will occur Saturday afternoon when instability is at its peak.
KEY MESSAGE 2, In the wake of the weekend front, a stiff NEerly breeze will develop and peak MON night into TUE. This will lead to building seas and elevated water levels. Astronomical tide levels will luckily be on the way down, but seas building to 7ft, though relatively choppy periodicity of 7 sec, but enough to lead to further beach and dune erosion concerns across the areas with severely diminished dune structures. Strongest winds of 20-25 kt with higher gusts expected MON night into TUE morning. Winds remain out of the N-NE into late- week, but speeds diminish to 10-15kt late TUE and beyond.
00z Saturday through Wednesday Main forecast concern tonight is the potential for fog/stratus development. Guidance is less bullish with developing it tonight with HREF/REFS probs only around 30-50% at best. Skies are expected to be mainly clear for most of the night with mainly thin high clouds, though could see increasing low clouds toward daybreak ahead of a cold front. There also may be slightly more mixing but guidance show a period of decoupling overnight. Confidence for fog development is low giving the pluses and minuses and generally have MVFR vsbys late tonight but there is some potential for lower cigs/vsbys than forecast. Any fog that develops is expected to dissipate fairly quickly after sunrise.
A cold front will drop into northern rtes Saturday morning and stall somewhere south of the Pamlico River in the afternoon. North of the front, expect MVFR to develop late morning and persist through the afternoon with the post frontal low level inversion. Along and south of the front there will be sufficent instabilty for shower and thunderstorm development bringing periods of sub-VFR conditions. Pw values will be surging to well above 2" and some storms could bring locally heavy rainfall. The front will push south through the area late afternoon and evening with convection waning with loss of instability. Ifr/lifr conditions expected to develop across all rtes with scattered showers continuing through Saturday evening.
Outlook: A risk of low CIGs and TSRA will accompany a wavy frontal boundary that will waffle north and south across ENC over the weekend. The front will finally shift fully offshore and away from the area Sunday night into Monday. The wind direction will vary during this time as well, but will become predominantly north to northeast behind the front Sunday night into early next week.
Benign boating conditions continue across ENC with light S-SWerly 5-10 kt winds and 1-2 ft seas across our area waters as high pressure persists offshore. S-SW winds build to 10-15kt late this afternoon Seas generally remain around 1-3 ft at 9-10 sec into early SAT morning.
Outlook (Sat through Tue): A front will be approaching the area from the NW and pass through with winds turning NNE and inc a bit to 10-20 kt for Nern marine zones by SAT afternoon. Increasing moisture plus weak instability lead to widespread showers with a few storms. At this time, conditions look to remain below SCA levels through the weekend, but a secondary front moves through Monday with SCA winds appearing likely later Mon into Tue with 15-25 kt winds and seas of 6+ ft.
Nc, none. Marine, none.
