Marine Weather and Tide Forecast for Severna Park, MD

KEY MESSAGES
- 1) Remnants of Isaias bring rain, breezy conditions, and potential for tornadoes today.

- 2) Above normal temperatures through mid week, then cooler conditions as moisture starved fronts move through.

DISCUSSION

KEY MESSAGE 1...Remnants of Isaias bring rain, breezy conditions, and potential for tornadoes today.

Rain associated with the remnants of Hurricane Isaias has overspread the entire region early this morning. Observations indicate most of this is light, though a few pockets of moderate rain have been reported in Central VA. A few stations along the central VA Blue Ridge have already measured over 1" of rain, with most of Central VA at or just above half an inch. Winds have also started picking up in the Alleghenies, with the strongest gust at 43mph in Garrett County.

Synoptically not much has changed as the remnant mid-level circulation of Isaias is now a large cutoff low over the TN Valley.
Forcing for ascent over the Mid-Atlantic is helping increase the coverage of rain. The interaction of the cutoff low to the west and surface high to the east will create a large area of convergence / broad frontal zone over the Mid-Atlantic. SPC Mesoanalysis indicates that PWATs of 2" are surging north into our area from NC and southern VA.

Rain totals are generally still around 1.5-2.5" across the area.
Orographic effects of easterly winds into the Blue Ridge will result in 3-4" of rain along the eastern slopes into the Piedmont. The Flood Watch in effect for those areas continues. Some of the high res models indicate the potential for enhanced rainfall over the DC metro late this evening as a surface wave of low pressure approaches then slows right around DC, before quickly departing to the east late tonight. Any additional rain in the metro area could certainly lead to flooding concerns, so will continue to monitor model and radar trends to see if the Flood Watch need to be expanded.

In terms of the severe weather threat, SPC has expanded the Slight Risk into most of Central VA, with a Marginal up into the I-81 corridor to the MD/PA border. Once the main shield of rain departs to the north this afternoon, most of the area enters a brief lull where we could see some breaks in the clouds. There's a better chance for this to occur over Central VA to Southern MD. A wave of surface low pressure then tracks through the area this afternoon. If this can take advantage of any present instability, there is more than enough shear to fuel organized severe convection. Model soundings still show elongated hodographs, so the tornado threat is going to be front and center, though damaging wind gusts are also possible. The biggest question mark remains how much instability can develop, and how far north that instability will reach. Right now, it appears the most favorable area is going to be east of the Blue Ridge and south of Route 50.

The Wind Advisory remains through late this morning for the Alleghenies and Blue Ridge where gusts of 45-50 mph are expected.
Elsewhere, breezy conditions develop late this morning into the afternoon, with the strongest gusts around 20-30 mph.

Another round of steady rain is likely tonight as the cutoff low aloft moves across the Mid-Atlantic. Precip comes to an end from west to east Monday morning as the remnants of Isaias finally push offshore. Humid and warm conditions for Monday afternoon, though most of the area is going to be dry.

KEY MESSAGE 2...Above normal temperatures through mid week, then cooler conditions as moisture starved fronts move through.

Brief ridging may bring high temperatures Tuesday and Wednesday to near 80 degrees. Low pressure passing north of the area will send a cold front southward sometime on Wednesday. Most of the rain likely remains across Pennsylvania, although some showers may sneak southward.

There remains significant model spread the progression of additional fronts and upper troughs at the end of this week into next weekend. However, the trend remains for cooler conditions as highs return closer to normal values for Thursday and Friday.

AVIATION /07Z SUNDAY THROUGH THURSDAY/
Conditions are deteriorating as a steady rain moves into the region.
IFR conditions are expected at all terminals by late morning, and remain that way through tonight. It is possible some breaks in the clouds occur this afternoon, but they build back in this evening.
Guidance is indicating the potential for LIFR CIGs late this evening. Conditions begin to quickly improve tonight as northwest winds take hold, with VFR conditions returning Monday morning.

Northwest winds gust around 20-25 knots Monday afternoon, then diminish Monday night into Tuesday. Prevailing VFR conditions are anticipated from Tuesday through Thursday. Passing showers Thursday night into Friday could bring brief sub-VFR conditions.

MARINE
SCA conditions expected to continue through tonight as the remnants of Isaias move across the region. Winds gust around 30 knots at times throughout the day, and some gusts to Gale force are possible.
It is becoming unlikely we see sustained Gale conditions, thus the Gale Warning is likely to be dropped for the central bay in the next couple of hours.

Clusters of thunderstorms are likely to move across parts of the waters this afternoon. It is possible that Special Marine Warnings may be needed for wind gusts in excess of 35-40 knots and possible waterspouts.

Winds over the waters diminish late tonight, but will pick back up Monday afternoon. Another round of SCAs is going to be needed to account for these northwest winds. Winds drop again Monday night.
Winds could fluctuate in & out of SCA criteria between Wednesday and Thursday as a cold front passes through.

TIDES/COASTAL FLOODING
Increasing onshore winds and elevated tide levels due to the New Moon will result in coastal flooding during the high tide this afternoon to evening. Coastal Flood Advisories have been issued for some locations, and it is possible additional ones need to be issued. For Annapolis, it is going to be close as to whether it reaches Moderate flood, so have maintained the Coastal Flood Watch for now. Water levels quickly decrease Monday morning as offshore winds follow.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Coastal Flood Watch from 3 PM EDT this afternoon through this evening for MDZ014.
Coastal Flood Advisory from 2 PM this afternoon to 6 PM EDT this evening for MDZ016.
Coastal Flood Advisory from 1 PM this afternoon to 6 PM EDT this evening for MDZ018.
Wind Advisory until 11 AM EDT this morning for MDZ509.
VA...Coastal Flood Advisory from 2 PM this afternoon to 6 PM EDT this evening for VAZ057.
Wind Advisory until 11 AM EDT this morning for VAZ507-508.
Flood Watch through late tonight for VAZ036>040-050-051-501- 502-507-508.
WV...Wind Advisory until 11 AM EDT this morning for WVZ501-505.
MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ530>533-535-536-538>542.
Small Craft Advisory until 5 AM EDT early this morning for ANZ534-537-543.
Small Craft Advisory from 11 AM this morning to 11 PM EDT this evening for ANZ534-537-543.
Gale Warning until 11 AM EDT this morning for ANZ534-537-543.