textproduct: Wakefield

WHAT HAS CHANGED

Confidence in rainfall has increased Sunday into early Monday.

KEY MESSAGES

1) Seasonable temperatures and dry through Saturday.

2) Moisture and rain chances return late this weekend into early next week.

DISCUSSION

As of 315 AM EDT Wednesday...

KEY MESSAGE 1...Seasonable temperatures and dry through Saturday.

A split flow pattern is observed on GOES water vapor channels early this morning with a northern stream in vicinity of the US/Canada border and a southern stream that extends across the southern tier of the US. At the surface, 1020mb high pressure is centered over the region. TD 9 is drifting slowly E in the western Gulf. Clear and cool early this morning with temperatures largely in the lower to mid 40s, with 50s at the immediate coast. Temperatures will still fall a few degrees over the next few hours, and typically cool spots could drop into the upper 30s. Patchy shallow ground fog is possible around sunrise, mainly in the interior coastal plain and Piedmont.

High pressure shifts offshore Wednesday with high temperatures moderating back to near average, which are in the lower to mid 70s. However, highs across the Eastern Shore will be a little cooler and in the upper 60s to lower 70s. The high shifts farther offshore Thursday with high temperatures rising into the upper 70s to lower 80s (potentially mid 80s well inland) ahead of another dry 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 what is forecast to become Hurricane Isaias.

KEY MESSAGE 2...Moisture and rain chances return late this weekend into early next week.

By Sunday and Monday, there is increasing confidence that moisture gets pulled northward and then pushed eastward across the region as the TC (forecast to become Hurricane Isaias) makes landfall and merges with an upper trough in vicinity of the Mid-South. Of the 00z/07 deterministic global models, the GFS and EC AIFS are more progressive showing the best rainfall potential in the early Sunday through Sunday evening timeframe, while the ECMWF and CMC are slower with a longer duration in the Sunday through early Monday timeframe. Heavy rain is possible as ample moisture will be present, 00z ensemble systems showing PW values at or above 200% of normal along with a plume of instability surging N ahead of the trough. There is still considerable spread between the 10th and 90th percentile QPF in the 00z/07 ensemble guidance (EPS/GEFS/GEPS). In general, the 10th percentile (reasonable low-end) accumulated precip through 00z Tuesday is 0.25-0.5" (hence increasing confidence of rainfall) while the 90th percentile is on the order of 1.5-3.0". Heavy rain is possible as ample moisture will be present, ensemble guidance showing PW values at or above 200% of normal along with a plume of instability surging N ahead of the trough. The overall consensus is for drier air conditions to arrive later Monday and continue into the middle of next week. Temperatures should remain near average late this weekend through the middle of next week.

AVIATION /07Z WEDNESDAY THROUGH SUNDAY/

As of 150 AM EDT Wednesday...

High pressure was centered over the region as of 06z. VFR with a calm to very light wind. VFR conditions are expected to prevail the next 24 hours. The only exception is some possible shallow ground early this morning, which could produce some brief vsby restrictions mainly at RIC and PHF. The wind becomes S to SE later this morning and increases to 5-8kt, and could shift to a sea-breeze induced ENE at ORF during the aftn given light flow. Mostly clear tonight with a very light southerly wind.

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 315 AM EDT Wednesday...

Key Messages:

- Generally light winds and benign conditions prevail through Saturday.

- Small Craft Advisories are likely late this weekend into early next week as a remnant tropical system tracks through the central US.

Surface high pressure is centered a few hundred miles offshore of the MD coast this morning. Winds are generally light and out of the east. As the high shifts offshore later today, winds shift to the S by this afternoon and then SW 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 is dependent on the future track of a tropical system, which is currently forecast to make landfall somewhere along the central Gulf coast Friday night. High pressure will retreat as the (remnant) tropical 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 is possible Sunday as the wind direction becomes SE, but exact specifics are difficult to highlight at this point. Regardless, a period of Small Craft Advisories seems likely early next week.

AKQ WATCHES/WARNINGS/ADVISORIES

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