textproduct: Wakefield

WHAT HAS CHANGED

Updated full discussion. Confidence in heavy rainfall and strong to severe storms continues to increase today as a shortwave/MCV moves across the area. A Slight Risk for Severe Storms has been introduced roughly along and east of I-95. A Flood Watch has been issued for the urban areas of SE VA from 1-10 PM today.

KEY MESSAGES

1) There is increasing confidence in numerous showers/storms this afternoon and early evening, especially east of I-95. There is the potential for scattered strong to severe storms and localized flash flooding in urban/flood prone areas. The main severe threat is damaging wind gusts, though an isolated tornado cannot be ruled out. A Flood Watch has been issued for the urban areas of SE VA.

2) A more summer-like pattern takes hold Wednesday night into the weekend.

DISCUSSION

As of 300 AM EDT Tuesday...

KEY MESSAGE 1...There is increasing confidence in numerous showers/storms this afternoon and early evening, especially east of I-95. There is the potential for scattered strong to severe storms and localized flash flooding in urban/flood prone areas. The main severe threat is damaging wind gusts, though an isolated tornado cannot be ruled out. A Flood Watch has been issued for the urban areas of SE VA.

Yesterday's convection has moved offshore and weakened, leaving behind a few showers across SE VA/NE NC. However, the actual cold front is still to the north of the FA. In addition, an upper shortwave/MCV is clearly evident on GOES satellite imagery over eastern TN. While the models have had varying solutions regarding the eventual evolution of this feature over the past day, there is now very good agreement that it will impact our area (especially along/east of I-95). As the aforementioned cold front gradually drops south through the area later today, a surface low will form and deepen along the front as that upper level feature now in TN tracks over the area. Even though convection impacted the area yesterday, temps should rise to near 90F in SE VA/NE NC with dew pts in the lower 70s. This will allow for plenty of sfc-based instability (~1500 J/kg of MLCAPE) to develop. Early/mid aftn temps may only be in the 70s NW of RIC with the front bisecting the area. The low is progged to enter SE VA during the afternoon, coinciding with peak heating. Showers are expected in the Piedmont by late morning as the shortwave/MCV approaches. Then, tstms will quickly develop along and ahead of it during the aftn and become fairly widespread as they get closer to the coast. The most likely timing for storms is 1-4 PM along the I-95 Corridor, and 2-6 PM closer to the coast. There is a threat for damaging wind gusts given sufficient sfc heating and enhanced mid/upper flow which will allow for some degree of storm organization, especially near the coast. In addition, there is a low but nonzero tornado threat near the center of the low (especially near the coast) where the LLVL flow could be locally backed. SPC has introduced Slight Risk for severe storms (Level 2 out of 5) near and east of I-95.

In addition to the severe threat, there is a threat for locally heavy rainfall, with the greatest concern near the coast along and a little bit to the north of the low track where some training of storms appears likely. With PWATs increasing to ~2.0", rainfall rates will be efficient. Both the REFS and HREF ensemble PMMs show an area of 2-4" near the coast, with the REFS being a bit farther south than the HREF. Also, the HREF has up to 30-50% 40km neighborhood probs of 3"/3 hours for most coastal zones N of the VA- NC border. So even though antecedent conditions have been dry, have issued a targeted Flood Watch for SE VA (mainly for the urban areas). These areas saw 1-2" of rain yesterday and localized totals of 3 to 5 inches are definitely possible in a few spots. This roughly aligns with WPCs Slight Risk for Excessive Rainfall (Level 2 out of 4). All convection should end by mid to late evening as the low moves offshore and drier air moves in behind the front. Comfortable tonight with lows in the upper 50s-60s.

KEY MESSAGE 2...A more summer-like pattern takes hold Wednesday night into the weekend.

A drier airmass will take over behind the cold front, keeping Wednesday dry. Temperatures won't be much cooler though, with highs near normal in the mid to upper 80s across the area Wednesday. By Wednesday night, winds will quickly shift back to the SE-S and bring back normal June humidity amd temperatures. For the remainder of the week, a more typical summertime pattern sets up. Upper heights gradually rise on Thu/Fri, with dry wx continuing on Thu and isolated aftn/evening storms possible Fri (mainly N/NW). There is a better chc of tstms Saturday aftn/evening as a more well defined shortwave crosses the area. Expect highs mainly in the upper 80s and low 90s, with overnight lows in the 60s to near 70F.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

As of 640 AM EDT Tuesday...

IFR stratus has pushed to the north of the terminals, with mostly VFR at this hour. Mainly VFR with some brief MVFR or IFR stratus possible at SBY this morning. Then, A low pressure system is progged to cross the area this afternoon-early evening, which will result in numerous showers/tstms from midday-early evening. Highest confidence in thunder is at ORF/PHF/ECG, where VCTS has been included. Some of the storms could produce gusty winds of 30-40+ kt, especially in SE VA/NE NC. As such, additional flight restrictions are likely later today, initially in SHRA/TSRA, and then with lingering low clouds into the evening (especially ORF/ECG). Conditions improve back to VFR tonight as drier air moves in from the N-NW.

Outlook: Mainly dry/VFR Wednesday. Late day showers/storms possible Thursday and Friday.

MARINE

As of 300 AM EDT Tuesday...

Key Messages:

- A cold front will move across the local waters this afternoon. Decent cold air advection forecast for behind the front has prompted the issuance of SCAs for the Bay and lower James this evening through early Wednesday morning.

- Benign, sub-SCA conditions are expected for much of the rest of the week.

A few light to moderate showers remain across the lower Bay and coastal waters this morning in the wake of the strong convection that moved through last night. Winds outside of storms have relaxed, with SSW winds of generally 10-15 kts being observed across the local waters. A low pressure system is currently moving across the Appalachians in northern West Virginia/southwestern PA. The associated cold front is slowly approaching the local waters from the west, and this feature will be the focus of today's weather, for both winds and thunderstorms.

Winds will remain around 10-15kt through the morning ahead of the front. Another surface low is forecast to develop along the front as it moves through the area, which introduces some uncertainty in winds ahead of the front. Have kept sub-SCA winds across all waters through the day today, but some guidance is suggesting that the gradient in the vicinity of the aforementioned low may tighten and bring a period of stronger winds. Some of this guidance may be showing the convectively driven winds in the strong to severe storms that are expected to develop with this low, which is why they have not been included. In-house wind probs also do not support rapidly increasing winds ahead of the front. In regards to the storms tomorrow, some of these storms may produce winds in excess of 50kt+ and isolated waterspouts, so SMWs will handle this. The timeframe for any storms moving across the local waters will be between 2 pm to just after sunset (+/- an hour or two).

In the wake of the front, a good surge of CAA is expected to push across the waters. Local wind probs for sustained winds of 18 kts across the Bay have increased to 70-90%, so SCAs have been issued to capture this brief NW wind surge between 20z-08z for the Bay, and 00z-05z for the lower James. A few gusts to ~25 kt are possible across the coastal waters, but confidence is not high enough to include an SCA for these marine zones at this time, especially since we are not expecting rapidly building seas due to the not quite as favorable wind direction (NW). After this brief wind surge, winds will quickly decrease across all waters as high pressure builds back over the region, with generally benign marine conditions expected for the remainder of the week.

While winds are forecast to increase late tomorrow, they will be parallel to the coast then becoming offshore, so the Rip Current Risk will drop to low. Low rip risk will likely remain through late week with the more benign conditions currently forecast.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...Flood Watch from 1 PM EDT this afternoon through this evening for VAZ089-090-097-098-523>525-528>531. MARINE...Small Craft Advisory from 4 PM this afternoon to 4 AM EDT Wednesday for ANZ630>632-634. Small Craft Advisory from 7 PM this evening to 1 AM EDT Wednesday for ANZ639.