Marine Weather and Tide Forecast for Glasgow, DE

KEY MESSAGES
1. A frontal system passes through the region later today and tonight producing widespread showers with localized flash flooding.

2. A trailing mid-level short wave trough and weak cold front lead to the potential for additional rounds of showers and thunderstorms on Monday.

3. A cold front is expected to cross through the region Wednesday night into Thursday resulting in more shower and thunderstorm chances.

DISCUSSION
KEY MESSAGE 1...A frontal system passes through the region later today and tonight producing widespread showers with localized flash flooding.

A mid level short wave trough will continue to progress eastward through tonight. A warm front ahead of that low, was over central PA and central NJ as of mid day. That front is expected to progress eastward into our region late this evening into the overnight hours.

A broad area of showers with rain rates ranging from a few hundredths of an inch per hour up to one quarter inch per hour continues to slide over the region. Because of the expansive cloud cover and how far removed from the main forcing this initial round is, expecting the main mode to be showers, though can't rule out an embedded isolated thunderstorm.

The focus is on a convective complex that developed over Ohio in the last few hours and is making progress eastward to the PA state line. Most high res guidance now shows this complex at least clipping portions of our region (although it should be noted, that they are for the most part a few hours too slow in the development of the MCS). That complex is not expected to be in our region until mid to late evening continuing into the overnight hours. By that point, instability should be more limited, so it still appears likely that this complex will weaken as it approaches. That being said, we will continue to monitor for the heavy rain and damaging wind threats.

It still looks as if precipitable water values will increase from around 2 inches now to 2.25 inches by late afternoon. While localized flash flooding is possible due to localized amounts of 1 to 2 inches of rain, the convective complex is likely to move through rather quickly. The Weather Prediction Center has a Marginal Risk for Excessive Rainfall, which is a 1 out of 4.
The Slight risk has been cut back to portions to southeast Pennsylvania west of Philadelphia.

The severe threat is fairly minimal, generally focused on Delmarva where the Storm Prediction Center has a Marginal Risk (1 out of 5) for Delmarva and extreme southern New Jersey.

KEY MESSAGE 2...A trailing mid-level short wave trough and weak cold front lead to the potential for additional rounds of showers and thunderstorms on Monday.

The cold front associated with the low that approaches the region on Sunday will finally progress through the region and move offshore on Monday. Additionally, in the the mid-levels, a trailing short wave trough will cross overhead. The net result is that isolated to scattered showers and thunderstorms will be possible primarily during the afternoon on Monday.

As for hazards, this round appears to have very limited threats for both flash flooding and severe weather. Convection on Monday will be much more weakly forced (as compared to Sunday/Sunday night), and bulk shear values are depicted in the 20 to 25 kt range, which is rather modest. Although there will be instability present, the modest shear will limit storm organization. Model soundings still depict relatively high precipitable water values of upwards of 2 inches, and warm cloud layers above 10K ft, which results in some heavy rain threat.
However, with limited shear and coverage of convection, the threat for any one area to get heavy rain for long enough to result in flash flooding remains low.

For those hoping for a significant cool down in the wake of this cold front, unfortunately the temperature gradient is very small. As such highs on Tuesday will be at or just a degree or two lower than Monday. That being said, the front should usher in drier air, so regardless it should feel more comfortable on Tuesday.

KEY MESSAGE 3...A cold front is expected to cross through the region Wednesday night into Thursday resulting in more shower and thunderstorm chances.

In the wake of Monday night's cold front, weak high pressure will briefly build into the region for Tuesday and much of Wednesday. An upper-low will traverse portions of Ontario and Quebec during this time, passing north of the region Wednesday night. To the south of the upper-low, broad troughing will be in place across much of the Northeast, with a few embedded shortwaves pivoting around the base of the trough. At the surface, a cold front will begin to approach the area late Wednesday, and cross through the region Wednesday night into Thursday.

Timing discrepancies remain with the frontal passage amongst model guidance. Some guidance indicates the front passing through the region primarily during the overnight hours Wednesday night and clearing the region Thursday morning, while there is still some guidance to suggest slower timing. At this point, timing uncertainties limit confidence in whether or not there will be any notable severe weather or flash flooding concerns, but this will continue to bear watching, particularly if the slower solutions come to fruition. For now, PoPs peak in the 40-60% range across most of the area on Thursday.

There are also some indications that the pattern may remain unsettled into the weekend as the front could get hung up just south of the region with a couple of areas of low pressure riding along it and mid-level troughing remaining in place. PoPs are currently in the 20-40% range each day due to the present uncertainties in timing and placement of these features.

In terms of temperatures, Tuesday and Wednesday look to be fairly warm with modestly increasing humidity. Highs look to be in the upper 80s to lower 90s. Temperatures currently look a bit cooler in the wake of the front, with highs in the low to mid 80s and lows in the upper 50s to mid 60s late this week and into the weekend.

AVIATION /19Z SUNDAY THROUGH FRIDAY/
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

Through 00Z...Periods of showers with MVFR ceilings and visibilities are possible through out the day time hours. A few TSRA possible after 21Z, but coverage will be limited, so haven't included it in the TAFs at this point due to low confidence in any one site being directly affected by TSRA. SE wind less than 10 kt, becoming S around 10 kt with gusts up to 20 kt. Moderate confidence overall.

From 00Z through 06Z...a convective complex is expected to approach the region as it weakens. Since it will be weakening, it is unclear if there will still be lightning associated with the complex if/when it moves over TAF sites. IFR ceilings are likely with and ahead of the line of storms.

After 06Z...once the showers and storms move off shore, ceilings will lower to LIFR late. S winds less than 10 kt.

Monday...ceilings should eventually increase to VFR, though isolated showers and thunderstorms after 18Z may result in temporary visibility and ceiling restrictions.

Outlook...

Monday night through Wednesday...VFR. No significant weather expected.

Wednesday night through Friday...Periods of scattered showers and perhaps storms are likely, with the greatest chance currently appearing to be late Wednesday night into Thursday.
Sub-VFR conditions are possible with any showers or storms.

MARINE
Winds and seas are expected to build by late this afternoon.
Therefore, the Small Craft Advisory remains in effect through tonight. Visibility restrictions are possible in showers and fog. A few thunderstorms possible as well.

Once seas subside below 5 ft on the ocean waters Monday Morning, winds and seas should remain below SCA criteria.

Outlook...

Monday night through Friday...No marine headlines currently anticipated with winds under 25 kts and seas under 5 feet.
Scattered showers and perhaps storms could lead to periods of visibility restrictions Wednesday night through Friday.

Rip Currents...

On Monday, southwest winds 15 to 20 mph with gusts up to 25 mph early in the morning will turn to be more west-southwest at 5-10 mph in the afternoon. Breaking waves will average 1 to 2 feet.
There will be an increasing southerly swell with a 5 to 7 second period. The result of these conditions is a LOW risk for the development of dangerous and life threatening rip currents for the Jersey Shore and Delaware Beaches.

For Tuesday, north-northeast winds 5 to 10 mph in the morning will gradually turn to be more southerly at 5 to 10 mph in the afternoon. Breaking waves will average 1 to 2 feet. There will continue to be a southeasterly swell with a 6 to 8 second period. The result of these conditions is a LOW risk for the development of dangerous and life threatening rip currents for the Jersey Shore and Delaware Beaches.

For specific beach forecasts, visit weather.gov/beach/phi

PHI WATCHES/WARNINGS/ADVISORIES
PA...None.
NJ...None.
DE...None.
MD...None.
MARINE...Small Craft Advisory until 4 AM EDT Monday for ANZ430-431.
Small Craft Advisory until 11 AM EDT Monday for ANZ450>455.