textproduct: Wakefield

WHAT HAS CHANGED

The cold front has trended slightly slower, leading to higher forecast temperatures across the southern half of the forecast area and the possibility for isolated strong storms this afternoon/evening.

KEY MESSAGES

1) There is a marginal risk for severe storms and localized heavy rain today.

2) An increasingly unsettled pattern takes shape through the Memorial Day weekend. Generally cooler to start, with periods of rain late this afternoon and Friday, followed by a lower- confidence temperature and rain forecast for late this weekend.

DISCUSSION

As of 1050 AM EDT Thursday...

KEY MESSAGE 1...There is a marginal risk for severe storms and localized heavy rain today.

Latest surface analysis depicted a cold front slowly moving south across far northern portions of the FA this morning. This front will continue to slowly move south through the day, acting as a focal point for convection. Meanwhile, a weak area of low pressure was noted across far E NC. A few light showers/sprinkles are possible across SE VA/NE NC from this low as it moves NE later today. Otherwise, a shortwave trough moves into the region this afternoon into this evening, allowing for enough ascent for scattered showers and storms to develop (mainly after 2 PM).

Ahead of the front, mostly sunny to partly cloudy skies have allowed for temps to warm into the upper 70s to lower 80s as of 1020 AM. Given more widespread clearing than originally anticipated, temps have already warmed above the previous forecast highs across northern portions of the FA. As such, have leaned towards the HRRR with temps and have increased temps with highs now expected to range from the mid 70s N to the lower 90s S. Temps cool into the upper 60s to lower 70s behind the front in the rain-cooled air with overnight lows in the low-mid 50s inland and mid-upper 60s along the coast.

The warmer temps this afternoon will help increase instability. As such, SPC has added a Marginal risk for severe storms for this afternoon and evening along and south of I-64. While deep layer shear will be weak, instability should be high enough to support a few strong to severe storms. Damaging winds are the primary threat given inverted-V soundings. However, will note that there is a mid-level warm nose on HRRR soundings which would result in substantially lower instability and shorter storms, limiting the severe potential.

Given the weak shear aloft, storm motions are expected to be slow, with model guidance showing the potential for training and nearly stationary showers/storms. If showers/storms do become nearly stationary or train, locally heavy rainfall would be possible. The 00z HREF shows a 10% chance for 3"/3hrs across far S VA/NE NC. However, the REFS has some of the heaviest bands farther to the north near the Richmond Metro. As such, some uncertainty remains regarding the exact corridor of heaviest rainfall potential. If the front is slower, the threat would extend farther north (potentially including Richmond), however, if it is faster, then the threat would be south of I-64. In any case, WPC has introduced a Marginal ERO for the potential for >3" of rain. However, given the drought, flash flood guidance is quite high, leading to low confidence in flooding. Therefore, the greatest threat is across urban areas. The severe and flooding potential wane overnight as the cold front moves south of the local area, ushering in cooler, more stable air.

KEY MESSAGE 2...An increasingly unsettled pattern takes shape through the Memorial Day weekend. Generally cooler to start, with periods of rain late this afternoon and Friday, followed by a lower- confidence temperature and rain forecast for late this weekend.

The cold front moves south of the local area overnight with high pressure building into New England. This will allow for a period of CAD developing tonight and lingering until Sunday. Forecast highs will remain in the 60s to 70s Friday with periods of mainly stratiform light rain and drizzle. Have maintained no mention of thunder on Friday due to the wedge and lack on instability present. There is still some uncertainty with respect to the durability of the cool air/CAD wedge setup heading into the weekend. Namely, because of the mid-level ridging, there continues to be a growing signal that the warm front remains pinned to our south a bit longer, therefore holding the wedge airmass in place through the first half of the weekend. This injects a bit more uncertainty into temperatures for Saturday as stable, low-level NE marine flow persists. The current forecast keeps the warmer temperatures (near 80F) confined to the SE, with a sharp temperature gradient from SE to NW, but this is subject to change if the front does not lift as quickly as currently forecast.

Eventually, the warm front does lift back north over the area to fully erode the CAD airmass later Sunday and Monday. Stagnant flow will then likely result in that weakening frontal boundary getting hung up over northern portions of the area late in the holiday weekend into early next week. This will lead to the potential for continued unsettled conditions lingering throughout the holiday weekend and into early next week. Cooler temperatures than currently in the forecast are quite possible Sunday, though quick warming is likely heading into early next week as mid-level ridging rebuilds east of the Rockies.

The unsettled pattern will allow for rain chances virtually every day today through the middle of next week. While the weekend certainly doesn't look to be a washout, rain chances will be higher than they've been of late each day into the middle of next week. The latest 00z GEFS averages 1.0"-1.5" area wide through Monday, with some areas mainly across southern VA and NE NC possibly seeing 1.5- 2.0", while the EPS averages 2.0"-2.5" across the entire forecast area, which is definitely on the higher end of guidance. Regardless, any rain will be beneficial with the ongoing drought.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

As of 200 PM EDT Thursday

A cold front slowly drops south across the local area this afternoon into this evening. Scattered showers and storms develop along the front this afternoon with more widespread showers expected behind the front tonight. While storms are possible this afternoon, confidence is generally low that any given storm will impact one of the terminals. As such, have opted for PROB30s to account for the uncertainty at ORF/PHF/ECG. The greatest chance for storms is south of RIC and west of ECG/ORF/PHF. However, since storms have begun to develop around RIC, have added a VCTS for that terminal. A few storms may have locally strong to severe winds and locally heavy rain with VIS reductions. Showers become lighter and more patchy on Friday. CIGs lower to MVFR behind the cold front with IFR CIGs becoming more widespread tonight (mainly after 6z). CIGs improve to MVFR at ECG by mid- late morning Fri, but likely remain IFR through the day Fri across the other terminals.

Outlook: Sub-VFR CIGs (potentially widespread IFR) are likely through at least Saturday for a majority of the area as a cool, wedge airmass develops over the area. Sub-VFR may linger through Sunday, especially NW. Conditions also become unsettled with numerous chances for rain through a majority of the weekend.

MARINE

As of 145 PM EDT Thursday...

Key Messages:

- A cold front drops south across the local waters through this evening. SCAs remain in effect for the Ches Bay and the lower James River now through Friday evening, and for the coastal waters north of the VA/NC border through Saturday evening. NE winds will average 15-20 kt with gusts to 25 kt, though gusts to 30 kt are possible over the northern coastal waters.

- Winds gradually diminish and become more variable this weekend, but 5 to 7 foot seas could linger across the northern coastal waters into late Sunday/Sunday evening.

Latest obs and buoy reports reflect NE-E winds of 10-15 kt across the local waters this afternoon, except SE winds off the northern OBX where the well advertised cold front has yet to reach that far south. Seas are 3 ft, with waves on the eastern VA Rivers, Currituck Sound, and Chesapeake Bay at 1-2 ft.

The front will continue to drop south across the souther marine area through this evening, before stalling just to our south on Friday and then slowly lifting back north over the upcoming weekend. A period of elevated NE winds is expected this afternoon through Friday evening, averaging 15-20 kt with gusts to 25 kt north of the VA-NC border, with winds a few knots higher over the coastal waters N of Cape Charles (where gusts to 25-30 kt are possible at times). Winds may struggle to increase as much in the far southern waters (especially S of VA Beach) due to the sluggish southward progression of the front.

Seas build to 5-7 ft (highest N) by tonight with waves of 3-4 ft on the Ches Bay. SCAs remain in effect for the Ches Bay and the lower James River now through Friday evening, and for the coastal waters north of the VA/NC border through Saturday evening. The front is still forecast to lift slowly north Friday night into Saturday morning, which will allow winds to diminish this weekend as the pressure gradient relaxes. If the frontal timing continues to lag farther into the day on Saturday, the northern waters could still see SCA winds linger through Saturday afternoon. Confidence in lighter (~10 kt), more variable winds is high from Saturday night through the remainder of the holiday weekend. However, 5 to 7 foot seas could linger north of Parramore Island through late Sunday evening in persistent E-NE swell, even after winds decrease.

Increasing seas in the wake of the cold front will produce a washing machine effect at all beaches to end the work and lasting through much (if not all) of the holiday weekend due to the lingering easterly, short-period swell. Hazardous surf zone conditions can be expected.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 1 AM EDT Saturday for ANZ630-631. Small Craft Advisory until 1 AM EDT Saturday for ANZ632-634. Small Craft Advisory until 10 PM EDT Friday for ANZ639. Small Craft Advisory until 7 PM EDT Saturday for ANZ650-652. Small Craft Advisory until 7 PM EDT Saturday for ANZ654-656.