Marine Weather and Tide Forecast for Ebony, VA

KEY MESSAGES
As of 256 AM Sunday...

1) Marginal risk (low probability and coverage) for shallow, rotating cells capable of an isolated spin-up/tornado or strong to locally damaging wind gust Sunday afternoon through Monday morning

2) Moderate Risk for severe storms Monday (higher coverage than usual and with isolated instances of significant severe, eg. EF2 or stronger tornado and 75 mph or greater gusts), with potential for mixed mode (discrete or semi-discrete supercells with all hazards ahead of a QLCS with widespread strong to locally damaging wind gusts and corridors of significant wind and/or mesovortex tornadoes)
and with timing of greatest risk between 10A-7P.

3) Cooler than normal temperatures expected early Tuesday through Wednesday night across central NC, with highs running 15–20 degrees below mid-March averages.

DISCUSSION
As of 256 AM Sunday...

KEY MESSAGE 1... Marginal risk (low probability and coverage) for shallow, rotating cells capable of an isolated spin-up/tornado or strong to locally damaging wind gust Sunday afternoon through Monday morning

Sunday Morning Update: Sfc analysis this morning depicted a warm front draped across the northern/western Piedmont. Further south, regional mosaic radar indicated a developing area of convection off the Florida/GA coastline embedded within a plume of higher PWAT and low-level moisture transport. With time, this plume of richer moisture will advect across central NC this afternoon and evening.
Latest guidance continues to highlight associated showers and possibly a few storms moving into the southern Piedmont/Sandhills this afternoon/evening before moving north and decaying later tonight. The low-end threat for mini supercells and associated isolated wind/tornado threat detailed below in the previous discussion remains valid given latest trends in observations and model guidance.

Previous discussion:

A couple of shortwave troughs now over the nrn Great Basin/nrn Rockies and cntl AB/SK, respectively, will become increasingly- phased as they amplify a synoptic trough sharply across the Plains and MS Valley Sun-Sun night. Standardized 500 mb height anomalies within the trough are forecast to be negative 4-5 sigma over the lwr/mid MS Valley by 12Z Mon. Preceding height falls and strengthening lwr/mid-tropospheric flow will result downstream of the trough and throughout much of the ern US, including into cntl NC late Sun and particularly Sun night.

At the surface, a ~1022 mb high now over ern NC will be overtaken by a stronger one that will strengthen from ~1025 mb over the Great Lakes this afternoon to 1030-1035 mb off the New England and nrn Middle Atlantic coast through early Sun, while extending swwd across the srn Middle Atlantic Piedmont. A warm front will strengthen on the periphery of the ridge and retreat nwwd across cntl NC, where ely/sely and onshore flow will favor modification of the antecedent continental/dry airmass and with surface dewpoint recovery into the 50s F Sun afternoon. Richer, more-maritime low-level moisture, along a separate frontal zone now extending across the ern Gulf and cntl FL peninsula, will be transported nwd and across the srn Middle Atlantic Piedmont and Coastal Plain Sun night-Mon morning, in response to the aforementioned strengthening wind fields/low-level jet.

Given the only modest low-level moisture recovery coincident with afternoon heating, instability will remain weak and confined primarily to the srn Piedmont and Sandhills; and point forecast soundings to varying degrees depict a warm/dry layer based around 700-800 mb. As such, any cells that develop in that environment, probably invof the warm front, will be shallow but modestly sheared amid veering wind profiles in that layer, with an associated conditional risk of at least transient mini-supercells capable of strong to locally damaging gusts and/or an isolated spin-up/tornado.
The latter risk would be more likely toward evening, as LCLs lower with nocturnal cooling, and strengthening low-level wind fields yield stronger SRH. As cells progress nwwd across the nrn Piedmont through evening, they should become increasingly elevated and/or weaken, through associated rain may briefly diabatically-strengthen/ reinforce the (wedge) front as it slows over w-cntl NC/VA.

A couple of additional, low probability/risks of severe will exist through Mon morning from 1) scattered cells moving onshore over sern/ern NC and into the vicinity of RAH's srn-cntl Coastal Plain and 2) with a risk of other scattered cells more-broadly throughout cntl NC, amid warm/moist advection and beneath the strengthening height falls aloft. Each regime would pose a risk of isolated tornadoes and strong to locally damaging gusts.

KEY MESSAGE 2... Moderate Risk for severe storms Monday (higher coverage than usual and with isolated instances of significant severe, eg. EF2 or stronger tornado and 75 mph or greater gusts), with potential for mixed mode (discrete or semi-discrete supercells with all hazards ahead of a QLCS with widespread strong to locally damaging wind gusts and corridors of significant wind and/or mesovortex tornadoes) and with timing of greatest risk between 10A- 7P.

Sunday Morning Update: Little change in thinking with this forecast package with pretty steady model progs over last several days. Given the expected extreme shear profiles, SPC has introduced a Moderate Risk driven primarily by a 60% SIG WIND, although strong tornadoes and large hail will certainly be possible as well. The detailed previous discussion below including potential severe hazards and timing remain valid at this juncture.

Previous Discussion:

An intense synoptic trough will pivot and lift across the TN/OH Valleys and Appalachians and Middle Atlantic Mon-Mon night. Strong, 50-150 meter mid-level height falls will result across cntl NC (strongest nw) through Mon evening, during which time mid-level flow will increase to around 100 kts in the right entrance region of an intense (~125 kt), 500 mb speed max.

At the surface, a QLCS will likely to be ongoing at 12Z Mon near the spine of the Appalachians, along or probably slightly preceding a strong, polar front. An effective cold front will likely result from the QLCS; and this boundary will probably serve as the wrn bound of severe risk, with weaker convection possible along the synoptic, polar/cold front during the evening. Timing of the QLCS will be most favorable for strongest diurnal heating from the ern Piedmont ewd, and especially in the Coastal Plain (I-95 corridor). Widespread, strong to locally damaging wind gusts will probably result along the length of the QLCS, with corridors of 55-75 mph and locally >75 mph in embedded bowing segments and/or mesovortices. The latter will also favor the development of isolated tornadoes, a couple of which could be strong. There is a lower predictability for discrete or semi-discrete supercells ahead of the QLCS and effective and synoptic cold fronts, also favored over the Coastal Plain of NC/VA.
Should some occur, they would pose a risk of all hazards, including large hail and also a risk of a strong tornado or two.

It will turn sharply colder behind the polar front Mon evening- night, with CAA-driven lows in the upr 20s-mid 30s.

KEY MESSAGE 3... Cooler than normal temperatures expected early Tuesday through Wednesday night across central NC, with highs running 15–20 degrees below mid-March averages.

In the wake of Monday’s cold front, cooler and drier air will filter into central North Carolina late Monday night into Tuesday. A broad upper-level trough settling over the eastern US will reinforce cold air advection through the day Tuesday, keeping temperatures below mid-March climatology.

High temperatures are expected to reach the mid 40s to near 50 across the region Tuesday, which is roughly 15-20 degrees below normal for this time of year. Breezy west to northwest winds may also persist through much of the day Tuesday, with early morning wind chills in the 20s. Tuesday night lows will be in the mid to upper 20s with some cooler spots in NW the low 20s.

AVIATION /06Z SUNDAY THROUGH THURSDAY/
As of 210 AM Sunday...

VFR conditions continue through at least 15Z with some high cirrus moving across the region. Conditions deteriorate mid-day as southerly flow increases moisture ahead of the approaching system.
Low-to-medium confidence on exact timing of initial precipitation; expect isolated to scattered storms between 15Z–18Z. TEMPO groups were added to all terminal sites to account for the intermittent activity. Ceilings trend to MVFR from west to east between 18Z–21Z, with medium confidence in for IFR/LIFR conditions after 00Z Monday.
Surface visibilities will degrade as the boundary layer saturates, with BR/FG likely reducing visibilities from 1/2 to 1 1/2 miles at most sites late Sunday night. A potent 40–50 kt LLJ at 2,000 ft will override a stable surface layer with light winds. Therefore medium to high confidence for LLWS at all terminals starting around 00Z Monday.

Outlook: Monday: LIFR/IFR persists through the morning with widespread SHRA/TSRA. LLWS remains a primary concern until frontal passage late Monday night. Winds will shift SW and become gusty (30+ kts) ahead of a line of storms. Rapid improvement to VFR after 00Z Tuesday as the front clears the region.
Tuesday-Wednesday: High confidence VFR. Strong high pressure builds in, bringing clear skies and drier air. Blustery WNW winds on Tuesday (15–20 kts) will diminish by Wednesday.
Thursday: Continued VFR. High pressure shifts offshore with winds veering southerly. Increasing high clouds, but no category restrictions expected through Thursday.

RAH WATCHES/WARNINGS/ADVISORIES
None.