textproduct: Wakefield

WHAT HAS CHANGED

Updated for 18z Aviation discussion.

KEY MESSAGES

1) Scattered showers possible this afternoon. A Marginal Risk of severe storms remains in place for today, mainly for isolated severe storms late this afternoon/evening.

2) 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 300 AM EDT Wednesday...

KEY MESSAGE 1...Scattered showers possible this afternoon. A Marginal Risk of Severe Storms remains in place for today, mainly for isolated severe storms late this afternoon/evening.

Latest analysis reveals strong low pressure over James Bay, with the attendant surface cold front draped across the northeast into the lower Ohio Valley. Low pressure developing along that boundary over northern KY/southern OH later this morning will slide into the northeast through midday. Meanwhile, A weak disturbance lifts north through the area, bringing an initial round of scattered showers across the local area later this morning into early this afternoon.

CAMs present a couple of scenarios for this afternoon's convection. The upshot remains that another round of showers and thunderstorms will be possible after a brief lull, as the trailing cold front crosses into the region late this afternoon and this evening. If minimal showers push into the area this morning, there will likely be some breaks in the overcast that will allow for at least some modest destabilization, and hence a stronger severe threat. It is for this reason that the SPC Marginal Risk remains in effect. Should that clearing and diurnal destabilization occur, the kinematics remain favorable for developing convection. 30-35kt of 0-6km bulk shear would support this organized storm development, and mid-level (h7-5) lapse rates between 6-7+ C/km could also allow for sustained updrafts, posing a risk for damaging winds, large hail, and even a non-zero risk of tornadoes. Conversely, if those clouds and more substantial shield of overrunning showers do cross into the region, the cloud cover will likely preclude much in the way of destabilization, with a subsequently minimal severe threat over our area. There's even a bit of a precip- split flavor evident in some of the CAMs in this scenario, which would limit QPF even further. As it is, the quick-moving nature of this system won't offer much beneficial rainfall to the region in most any scenario. And given trends, have lowered QPF slightly to < 0.25" for most of the area.

KEY MESSAGE 2...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 eastern Canada drifts across northern New England, as a strong, but compact upper low pushes across the southern tier of CONUS, moving from Baja California Thursday to the Southern Plains and Mid-South by Friday and Fri night. The GFS Ensemble has trended toward the flatter/more suppressed and slower ECMWF solution, with the system moving across the Gulf coast, and the attendant surface low pushing along the Carolina coast Saturday, pushing some light rain into Hampton Roads and NE NC. In terms of sensible wx, it is looking more likely that the best rain chances and QPF remain to our south Saturday and Saturday night. The latest ensembles show the possibility of a light rainfall mainly across the southern half of the area on Saturday, but probabilities of QPF > 0.1" are 40-70%, so not expecting a drought buster by any means.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

As of 150 PM EDT Tuesday ...

VFR conditions prevail at the start of the 18z/29 TAF period. A cold front approaches the area, expected to cross after 22z/6pm. A few light pre-frontal showers are possible this afternoon, but the latest hi-res guidance shows the showers decreasing in coverage as they move eastward, so have only included VCSH for RIC and SBY, where showers are more likely. Then with the front, isolated showers and storms are possible at all terminals. Confidence in the convection reaching any given terminal is not high enough to have prevailing conditions, so have included TEMPOs for SBY/RIC/PHF and PROB30s for ECG/ORF. Mostly short lived flight restrictions are possible with the front. Winds will remain SE through this evening, becoming NE ~10 kt behind the front. A few gusts near 20 kt is possible.

Outlook: Conditions will return to VFR by THursday morning and lasting through Friday. Another storm system approaches the area on Saturday, bringing potential for additional flight restrictions Saturday into Sat night

MARINE

As of 215 AM EDT Wednesday...

Key Messages:

- A cold front approaches the region today and crosses the waters late tonight with increasing SE winds ahead of and NW winds behind the front.

- Nuisance to low-end minor tidal flooding is possible tonight, primarily for bay-facing portions of Dorchester County, MD.

Surface high pressure is slowly translating offshore early this morning ahead of the next cold front. Winds are mainly SE 5-10 kt on the back side of the departing high. Waves in the bay are around 1 ft with seas 3=4 ft. The pressure gradient is forecast to tighten by this afternoon as a surface trough/low and cold front approach the region. Opted to raise SCA flags for the Ches Bay as SE winds increase to 15-20 kt with gusts to 25 kt this afternoon and evening. Showers and a few storms with gusty winds are possible this evening ahead of the cold front. Guidance shows a substantial lull in the winds late this evening until the surface cold front sweeps south and east late tonight. Given 6+ hours of sub-advisory conditions, will not include headlines for the stronger post-frontal wind surge with this forecast package. Behind the front, winds become NW and increase to 20-25 kt with gusts 25-30 kt. The gradient will be steepest across the northern half of the area with somewhat lower winds expected from the mouth of the bay southward into NC. Waves in the bay will average 2-3 ft in the prefrontal SE winds this afternoon/evening and increase to 3-4 ft late tonight into Thursday. Seas continue to run below wave guidance but should increase to 4-5 ft away from the immediate coast in the stronger NW winds late tonight and Thursday. Seas in the 20-60 NM zones will build to 5-7 ft on Thursday. High pressure builds back into the area later Thursday into Friday. Another system likely skirts to our south on Saturday with some potential for SCA conditions across the southern waters.

Coastal Flooding...With elevated seas and a modest increase in southerly flow this evening, some minor to nuisance tidal flooding is forecast across the upper bay, primarily for bay-facing portions of Dorchester County. A Coastal Flood Advisory or Statement may be necessary for tonight's high tide cycle.

AKQ WATCHES/WARNINGS/ADVISORIES

MD...Coastal Flood Advisory from 10 PM this evening to 6 AM EDT Thursday for MDZ021>023. NC...None. VA...Coastal Flood Advisory from 11 PM this evening to 4 AM EDT Thursday for VAZ075-077. MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ630>632-634.