textproduct: Wakefield

WHAT HAS CHANGED

Updated 00Z TAF/aviation discussion.

KEY MESSAGES

1) Scattered showers and storms are possible across the northern tier of counties this evening into early Wednesday. A low-end threat for an isolated strong to severe storms also exists over the Northern Neck and Lower Eastern Shore late tonight.

2) Heating up on Thursday, then shower/storm chances return Thursday evening, potentially lingering into Friday morning.

3) Strong to severe storms are possible Thursday night. Lingering showers are possible Friday morning. Gradual clearing late Friday and Friday night looks to give way to a mainly dry, pleasant weekend.

DISCUSSION

As of 200 PM EDT Tuesday...

KEY MESSAGE 1....Scattered showers and storms are possible across the northern tier of counties this evening into early Wednesday. A low-end threat for an isolated strong to severe storms also exists over the Northern Neck and Lower Eastern Shore late tonight.

Low pressure over the NC OBX will lift northeast offshore of the Mid-Atlantic coast tonight. As it does so, it will pull a stalled frontal boundary back north as a warm front this evening into early Wednesday morning. There is decent agreement among the 12z CAMs that this feature will trigger weak convection late tonight. Scattered showers are possible, mainly along the coast, with a stronger storm or two possible within a marginally unstable environment just ahead of the front over the Northern Neck and Lower Eastern Shore. SPC has introduced a Marginal Risk (Level 1 of 5) over this northeastern portion of the forecast area, primarily for small hail and gusty winds.

KEY MESSAGE 2...Heating up on Thursday, then shower/storm chances return Thursday evening, potentially lingering into Friday morning.

Behind the warm front, a warmer and slightly more humid airmass pushes into the region Wednesday through Thursday, maintaining mainly dry conditions through at least midday Thursday. An upper trough and associated cold front will approach from the west on Thursday, allowing compressional heating to ramp up ahead of the boundary. Highs look to warm into the upper 80s to around 90F on Wednesday, then surge well into the mid-to-upper 90s on Thursday on increasingly breezy SSW winds. Heat indices top out around 100F on Wednesday.

For Thursday, deep afternoon mixing from W-SW downslope flow should help to mix out moist early morning low-level dewpoints, making for at least a drier feeling afternoon. Nevertheless, very warm to hot ambient temps should still yield Heat Index values in the 100 to 105F range. Heat headlines may ultimately be needed for portions of the area. For now will outline heat potential in the HWO.

KEY MESSAGE 3...Strong to severe storms are possible Thursday evening. Lingering showers are possible Friday morning. Gradual clearing late Friday and Friday night looks to give way to a mainly dry, pleasant weekend

Model trends continue to lean slower with the frontal passage Thursday night into Friday. Given this slower timing and the pre-frontal downslope flow, the window for showers and storms has also trended later into the evening and overnight hours. While later diurnal timing typically mitigates the severe threat, a window remains during the evening where lingering instability and high DCAPE (exceeding 1000 J/kg) could support a few strong to severe downbursts, focused along a shortwave trough lifting across the region ahead of the main front.

In terms of kinematics/storm mode, 25-30 kt of deep-layer bulk shear forecast across our northern tier favors a more discrete or loosely-organized multicell storm mode, with the stronger forcing and higher shear profiles displaced to our north and northeast. Because of the inverted-V signature evident on forecast soundings, indicative of the high-DCAPE environment locally, any storms that do push into our area are more likely to be cold-pool dominant. For that reason, the prevailing thought at this time is that the primary threat will be from localized convective outflows or gust fronts producing isolated damaging wind gusts. The highest probabilities for this remain focused across the VA Piedmont into the RIC metro and Northern Neck for Thursday evening. Will outline this severe threat in the HWO.

Another northern stream shortwave, attendant to a potent upper low over central Canada, will ultimately push the slow-moving cold front through the region Friday morning. Rain is likely during this period, as Gulf moisture overruns the boundary as it drops through the region. While some welcome measurable rainfall does seem likely, this synoptic setup typically limits the period for appreciable rainfall, as rapid clearing becomes increasingly likely Friday afternoon and night as the front sweeps south. Furthermore, the signal from multi-model guidance is trending toward keeping moisture associated with a potential tropical system well to our south over the Gulf/Southeast, offering no additional rainfall opportunities.

In terms of sensible weather, trends continue to favor a dry weekend, with seasonable temperatures and lower humidity levels.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

As of 750 PM EDT Tuesday...

A weak area of low pressure along the NC Outer Banks lifts slowly northeast through late tonight, and will lift a weak front back north as a warm front. This will maintain increased mid to high level cloud cover through tonight, especially across the SE terminals. While most terminals should remain VFR, ECG has already dropped to MVFR (~2000 ft) CIGs. MVFR CIGs could continue at ECG through ~7z Wed. Additionally, some model guidance tries to bring MVFR or IFR CIGs to ORF overnight. However, confidence was too low to include lower CIGs in the ORF TAF at this time. Outside of CIGs, there is a low-end chance for a few isolated showers at ORF/ECG/SBY overnight. That being said, confidence continues to decrease in this scenario. As such, have removed TEMPOs for ORF/ECG. For SBY, an isolated shower or storm remains possible mainly between 8-11z Wed. If a stronger storm was to develop, hail, gusty winds, and lightning would be possible. However, confidence remains low, particularly for deeper convection/lightning. Therefore, went with a PROB30 for showers at this time. Clouds clear from W to E Wed morning with mostly sunny skies expected Wed afternoon. Otherwise, light and variable winds tonight become WSW/SW 5-10 kt Wed apart from a sea/bay breeze moving onshore during the afternoon (likely impacting ORF).

Outlook: VFR conditions are expected to continue Wednesday night through Thursday evening, with showers/storms possible mainly Thu evening into early Fri with lingering showers and embedded storms into Fri afternoon. Drier conditions/VFR conditions return late Fri into the upcoming weekend.

MARINE

As of 240 PM EDT Tuesday...

Key Message:

- High pressure brings generally benign marine conditions through Wednesday.

- A period of elevated SW winds is likely Wednesday night into Thursday night with SCA conditions likely.

A front is draped to our south and west this afternoon with weak low pressure noted off the southern/central NC coast. Winds are mainly from the E at 5-10 kt. Waves in the bay are around 1 ft with seas 2- 3 ft. The warm front lifts northward this evening into tonight with winds becoming SE 10-15 kt behind the boundary. A few storms are possible very late tonight, primarily across the central/northern Chesapeake Bay and northern coastal waters. The main threat from any convection that manages to form will be gusty winds. Sub-SCA conditions are expected to continue until the gradient tightens ahead of the next front late Wednesday night into Thursday. SW winds increase, averaging 15 to 20 knots with gusts to 25+ knots as a cold front begins to approach from the NW and strong low pressure develops north of the area. Waves build to 2-3 ft in the bay with seas building to 4-6 ft near shore (highest N). SCAs will likely be needed for the Chesapeake Bay and tidal rivers, as well as a majority of the coastal waters starting Thursday morning and continuing into at least the first half of Thursday night. Winds will be a little stronger in the 20-60nm zones Thursday and Thursday night with gusts around 30 kt, but the latest model runs and local wind probs have backed off a bit with the wind magnitude vs the overnight guidance. Seas build to 5-8 ft during this period well offshore. Showers and storms are possible ahead of the cold front with gusty winds and locally higher waves/seas. The cold front drops across the local waters on Friday with winds shifting to the N/NW behind the front (sub-SCA). Winds diminish Saturday into Sunday as high pressure builds into the area. Winds and seas may increase again early next week as another system approaches the region.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...None.