textproduct: Wakefield

WHAT HAS CHANGED

Updated key messages and 12z Aviation Discussion. Rain chances have slightly decreased for this afternoon. There remains a conditional severe threat Wednesday afternoon and evening and rain chances have increased for this coming weekend.

KEY MESSAGES

1) Partly to mostly cloudy today. Some scattered showers will be possible through midday, mainly along and west of I-95.

2) Showers and storms expected on Wednesday. Some storms could be strong to severe.

3) Mainly dry to end the week, with rain chances returning by Saturday, though drought conditions are also likely to persist. Temperatures hover near or just below seasonal averages.

DISCUSSION

As of 650 AM EDT Tuesday...

KEY MESSAGE 1...Partly to mostly cloudy today. Some scattered showers will be possible through midday, mainly along and west of I-95.

Weakening 1024+mb high pressure remains in place along the mid- Atlantic coast early this morning, but will slowly move offshore through this evening. Clouds will thicken and lower through the day, especially inland.

Afternoon highs will be mainly in the upper 60s to lower 70s. The high pressure should keep the majority of the CWA dry. However, weakening upstream convection from showers and storms that moved across the Ohio Valley earlier this morning will cross the central Appalachians this morning, approaching western portions of our area this morning. A low (20-40%) chance for scattered showers remains in the forecast, with the best chance along and west of I-95 through midday. 00z/28 CAMs remain less aggressive regarding QPF potential across our area, the vast majority of guidance continues to show meager amounts less than 0.1" across the west, with some scattered, light rain showers along the I-95 corridor likely amounting up to a few hundredths at best. Partial clearing this afternoon and early evening before clouds increase again late.

KEY MESSAGE 2...Showers and storms expected on Wednesday. Some storms could be strong to severe.

Quasi-zonal flow aloft to begin the day on Wednesday. By later in the day, however a pair of mid-level shortwaves approach the area; The initial shortwave from the mid-south crosses the region late tonight into Wednesday first from the Ohio Valley, with the second disturbance crossing north of the local area Wednesday night. At the surface, low pressure tracks across the lower Ohio Valley into the interior northeast Wed morning. It is with the passage of the warm front that the first slug of overrunning showers will arrive Wednesday morning.

More importantly, this initial batch of light showers will impact the amount of clearing and hence the available instability in place across the local area when the second disturbance crosses the area Wed afternoon. As a result, while a convective threat exists over the local area for Wednesday afternoon and evening, it is still very much a conditional one. CAMs are coalescing behind clearing showers out by midday Wednesday, with the potential for some partial clearing in the piedmont out ahead of the cold front. Should this midday clearing occur, the combination of modest destabilization and 30-35kt of 0-6km bulk shear would support organized storm development. Given mid-level (h5-h7) lapse rates of 6-7 C/km, any sustained updrafts would pose a risk for damaging wind gusts. SPC has maintained a Marginal Risk (Level 1/5) for the region; however, if confidence in clearing increases, an upgrade may be warranted in subsequent outlooks.

KEY MESSAGE 3...Mainly dry to end the week, with rain chances returning by Saturday, though drought conditions are also likely to persist. Temperatures hover near or just below seasonal averages.

Still looking like a rather blocky pattern setup aloft for the late week into the weekend. The slow-moving low over the upper Great Lakes into Ontario drifts across northern New England into Quebec, as an upper low currently over the Desert Southwest slowly traverses the southern tier of CONUS, moving from Baja California Thu to the Southern Plains and mid-south by Friday and Fri night. The latest ECMWF and its ensemble mean remain far slower with this system. Meanwhile, the 00z/28 GEFS and GEPS each are a bit more progressive, and as a result show the system getting ultimately absorbed by the sprawling northern stream trough then ejecting NE across the area on Saturday. In terms of sensible wx, the current EPS/EC solution would yield some very light rainfall amounts across the local area, while the current GEFS/GEPS solution could portend a more substantial soaking rainfall. It should be noted that the EPS solution does fit the antecedent drier and more blocky pattern, but nonetheless PoPs remain in the 40-60% range for right now and model trends will continue to be monitored in the coming days.

MARINE

As of 220 AM EDT Tuesday...

Key Messages:

- Small Craft headlines remain in effect for all ocean zones due to lingering 5 foot seas.

- A cold front approaches the region Wednesday and crosses the waters early Thursday with increasing NW winds behind the front.

- Nuisance to low-end minor tidal flooding is possible Wednesday night for the upper Bay.

1024mb high pressure is over the region early this morning with generally light (~5kt) onshore winds. Waves in the bay are around 1 foot with seas 3-5 ft offshore. High pressure will dominate the local weather today into tonight before translating offshore on Wednesday ahead of the next cold front. Winds will transition to SE tonight, generally maintaining 5-10 kt. The pressure gradient tightens on Wednesday with SE flow around 15 kt and gusts 20 kt. Showers and storms are possible along and ahead of the front with gusty winds the main threat. Flow becomes NW and strengthens to 20- 25 kt with gusts 25-30 kt behind the front by early Thursday. Waves increase to 3-4 ft in the post-frontal NW surge on Thursday. High pressure builds back into the area later Thursday into Friday.

SCA headlines currently remain in effect for the coastal waters through early Wednesday morning due to 5 ft seas. Guidance has been running quite a bit above buoy observations so far this morning. After discussing with neighboring offices, have decided to maintain the current headlines as guidance shows heights increasing again by early this afternoon. May be able to cancel a bit early if these observational trends continue today. Seas will build again Wednesday night into Thursday in the post-frontal NW flow but the highest seas should become confined to areas well away from the coast in offshore flow.

Coastal Flooding...With elevated seas into midweek, and a modest increase in southerly flow Wed, some minor to nuisance tidal flooding will be possible across the upper Bay from Lewisetta to the Bayside of the MD eastern shore with the high tide cycle Wed evening/Wed night.

MARINE

As of 325 PM EDT Monday...

Key Messages:

- Small Craft Advisory (SCA) headlines remain in effect for the mouth of the Bay/Ocean, but have been discontinued elsewhere.

- Nuisance-type tidal flooding is possible Wednesday night for the upper Bay.

Surface high pressure has started to settle into the local waters this afternoon, with winds decreasing to ~10 kt or less for most of the region, with somewhat higher winds of 15-20kt confined to the Ocean offshore of far SE VA and NE NC. SCAs have been cancelled for all zones minus the Ocean (mainly for seas at or above 5 ft), and for the mouth of the Chesapeake Bay where waves will linger around 4 ft tonight. Seas tonight will be highest well offshore (6-8 ft) and across the nearshore NC waters (5-7 ft). The high becomes centered farther offshore Tuesday, as the next fast moving low pressure system tracks well to our NW across Canada. Winds become E to SE but remain fairly light on Tuesday, with some onshore/Bay/river breeze enhancement late Tue aftn/evening. Seas will generally remain ~5 ft Tuesday despite the minimal winds. A stronger frontal boundary approaches from the W on Wednesday, bringing a period with elevated S-SE winds, but for the most part, this looks to stay just below SCA thresholds. Some convective enhancement is possible Wed aftn/evening that could bring locally higher wind gusts. The front moves through late Wed night/early Thursday, and a surge for NW winds of 20-25 kt is expected, so SCA headlines will likely be needed for most, if not the entire marine area.

Coastal Flooding...Predominant ebb currents led to lower than expected water levels over the past 1-2 days in the lower Ches Bay/tidal rivers despite a good surge of onshore/NE flow. No additional statements will be needed. With elevated seas into midweek, and a modest increase in southerly flow Wed, some minor to nuisance tidal flooding will be possible across the upper Bay from Lewisetta to the Bayside of the MD eastern shore with the high tide cycle Wed evening/Wed night.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...None. NC...None. VA...None. MARINE...Small Craft Advisory until 6 AM EDT Wednesday for ANZ650-652- 654-656-658.