textproduct: Wakefield

WHAT HAS CHANGED

Confidence in rainfall has increased Saturday night into early Monday from remnants of Tropical Storm Isaias.

KEY MESSAGES

1) Seasonable to slightly above average temperatures and dry conditions through Saturday.

2) Moisture and rain chances return Saturday night into early Monday.

DISCUSSION

As of 310 PM EDT Wednesday...

KEY MESSAGE 1...Seasonable to slightly above average temperatures and dry conditions through Saturday.

High pressure remains centered over the area extending across the southeast CONUS to offshore New England this afternoon. An upper level trough over north central Canada will continue pushing the high pressure further offshore tonight and Thursday, as well as dragging a weak cold front across the area Thursday night. Additionally, Tropical Storm Isaias sits in the southwestern Gulf, slowly drifting east before making a northern turn. Temperatures today have moderated back to near normal, sitting in the lower to mid 70s, with the exception of the immediate coast and Eastern Shore which are in the upper 60s. Tonight's lows won't be as chilly as last night, with expected lows in the mid 50s inland and upper 50s along the coast. With the high pressure shifting more offshore Thursday, temperatures will rise to the upper 70s to lower 80s (mid 80s inland) ahead of the aforementioned cold front. This cold front crosses the region Thursday night with temperatures trending down to near seasonal averages Friday and Saturday. Dry conditions continue through Saturday. However, a gradual increase in high levels clouds is expected as upper level moisture spreads over the region well in advance of remnants of Tropical Storm Isaias.

KEY MESSAGE 2...Moisture and rain chances return Saturday night into early Monday.

By Sunday and Monday, there is increasing confidence that moisture gets pulled northward and then pushed eastward across the region as Isaias makes landfall and merges with an upper trough in vicinity of the Mid-South. The 12z/07 global models have came into better agreement of rainfall timing showing late Saturday night/early Sunday morning timeframe. Heavy rain is possible as ample moisture will be present, 12z ensemble guidance continuing to show PW values at or above 200% of normal along with a plume of instability surging N ahead of the trough. However, there is still considerable spread between the 10th and 90th percentile QPF in the 12z/07 ensemble guidance. In general, the 10th percentile (reasonable low-end) accumulated precip through 00z Tuesday is 0.25-0.5", while the 90th percentile is on the order of 1.5-3.0". The 50th percentile (most likely case) shows a generalized 0.75-1.25" of rainfall, with the highest rainfall totals in the souther half of the area. PoPs have increased to 90-95% from late Saturday night to early Monday morning to account for the increased confidence. Behind this system, drier air will filter back in later Monday through the middle of the week. Temperatures should remain near average late this weekend through the middle of next week.

AVIATION /19Z WEDNESDAY THROUGH MONDAY/

As of 125 PM EDT Wednesday...

High pressure remains centered over the region this afternoon. VFR conditions are expected to prevail through the 18z/07 TAF period. Winds are light around 5-10kt generally out of the S-SE. Winds at ORF are ENE due to the sea-breeze this afternoon. Clear skies will continue through tonight with very light S-SW winds.

Outlook: VFR conditions continue through much of the week. The next chance for sub-VFR conditions does not arrive until late this weekend.

MARINE

As of 300 PM EDT Wednesday...

Key Messages:

- Sub-SCA conditions prevail through Saturday.

- Small Craft Advisories are likely late this weekend into early next week as the remnant tropical system tracks through the central US, with high pressure well off the east coast.

Surface high pressure is centered offshore of the Delmarva this afternoon. Winds are generally light and out of the E-SE, with seas only 1-2 ft and waves in the Bay/rivers generally 1 foot or less. Winds shift to the S into this evening, and then to the SW later tonight. Those SW winds could frequently gust to ~20 kt, especially N of New Point Comfort in the Chesapeake Bay and N of Cape Charles on the ocean. However, don't expect any need for SCAs at this time. Light winds return for Thursday as the pressure gradient again slackens, with weak afternoon sea/bay breezes expected. A weak cold front moves through overnight Thursday and northerly winds increase to 10-15 kt by early Friday morning. Lighter winds return Friday afternoon with high pressure again settling over the area.

The marine forecast over the weekend continues to be dependent on the future track of the remnant low of tropical cyclone Isaias, which is currently forecast to make landfall somewhere along the central Gulf coast Friday night. High pressure will retreat as the (remnant) system moves northward through the TN Valley and easterly winds are expected to slowly expected to increase by Saturday over the local waters. A further increase in winds, and a shift to the S-SE is expected Sunday, but exact specifics are difficult to highlight at this point. Regardless, a period of Small Craft Advisories is likely Sunday-Monday

AKQ WATCHES/WARNINGS/ADVISORIES

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