Marine Weather and Tide Forecast for Thornburg, PA

NEAR TERM /THROUGH MONDAY/
KEY MESSAGES:

- A few thunderstorms are possible later tonight.

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Evening Update:

High pressure will continue to keep the area dry at least through 03Z. The warm front will begin to lift north during the overnight. There will be a bit of elevated instability and thus the potential for a few thunderstorms after 04Z. This development will continue through dawn. With the instability and mid and upper level cloud cover, this will keep fog to a minimum.

Previous Discussion:

Increase subsidence in the wake of the cold front has cleared a majority of mid and low-level clouds across the region.

Temperatures will still trend above-average this afternoon despite northerly flow at the surface.

Surface winds will gradually shift from north to southeast throughout the day as a new low pressure tracks into the Ohio River Valley. Mid and upper-level clouds will increase from south to north this evening, ahead of an expected warm front.

SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/
KEY MESSAGES:

- Warm front returns early Monday morning, before dawn - Showers and gusty thunderstorms Monday afternoon/evening with a cold front - Dry Tuesday under high pressure -------------------------------------------------------------------

The probability of showers and isolated thunderstorms increases to 35-50% with a passing warm front between 2am to 4am Monday morning. With elevated instability ranging between 300J/kg to 700J/kg and effective shear near 35kts, small hail could be observed in isolated thunderstorms. However, confidence at the moment is considered low given high resolution models showing a large range in the available instability aloft, some models go as high as 1000J/kg while others suggest only 300J/kg. If one were to see experience lightning and hail, it would likely be near I-80.

In the wake of the warm front, there will likely be a period where precipitation chances remain low. Mostly between 6am to 12pm, ahead of a cold front.

The trough and associated surface cold front are progged to advance eastward early Monday afternoon. A band of showers and thunderstorms are expected to develop along and ahead of the front, with increasing moisture and vorticity advection. A pre-frontal trough could also result in additional showers/storms ahead of the main front. A jet aloft will also enhance ascent, as well as shear. CAPE will also increase ahead of the front, with current HRRR progs between 500 and 1000 J/kg.
The amount of destabilization that occurs will depend on the timing of the front, and the effects a prefrontal trough will have on the atmosphere, though at this time it appears there is at least some potential for gusty wind (40-45mph) in storms between 2pm to 6pm.

Shower and thunderstorm chances will end from west to east Monday evening (between 7pm to 9pm) in the wake of the cold front.

Dry weather returns Tuesday as surface high pressure builds across the Upper Ohio Valley region.

Temperatures are expected to average above seasonable levels through the period.

LONG TERM /WEDNESDAY THROUGH SUNDAY/
KEY MESSAGES:

- Above normal temperature for the end of the week before a potential weekend cool off.
- Trending towards a wetter later half of week and start to the weekend.
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Confidence is fairly high on subtle Tennessee River Valley ridging aloft combining with surface high pressure to promote dry weather Wednesday. Temperature is likely to be above normal, but the degree of heating will depend on ridge strength (stronger equates to warmer) or influence of shortwave movement to the north (lowers heights and increases cloud cover to decrease temperature).

Ensemble models are trending toward a wetter outlook to end the week as potential shortwave movement increases within the quasi-zonal to weakly southwest flow overhead. There remains variations on shortwave timing and whether movement from the SW is able to phase with trough activity in southern Canada, but current cluster analysis suggests total accumulations are not likely to be impactful and environmental conditions will struggle to support hazardous weather.

From there, ensemble means suggest a more organized northern stream trough will drop toward the northeast U.S. next weekend as ridge development occurs over the Central Plains. This pattern favors near to slightly below average temperature and drier weather, but large variations in trough depth/progression will play role in the degree of cooling/drying as well as how quickly warm weather returns the following week.

AVIATION /01Z MONDAY THROUGH FRIDAY/
VFR will continue through tomorrow afternoon. Winds are expected to shift from northeast to southeast ahead of a warm front.

A passing warm front early tomorrow morning may create isolated restrictions and thunderstorms between 06Z to 10Z. PROB30 covers lightning potential in the vicinity of terminals that could experience impacts. During this time, expect brief periods of low-level wind shear for about 2 hours at most terminals.

There will be a briefing break in shower and thunderstorm activity ahead of a cold front. Probability of lightning and strong winds embedded within thunderstorms increases after 17Z with a pre-frontal trough followed by the cold front.

During the cold front passage, expect some temporary periods of MVFR ceilings. At FKL and DUJ, expect MVFR CIGS to settle into the area through Tuesday morning.

Outlook...
VFR and mostly dry weather return Tuesday and Wednesday, followed by another weather system bringing increasing chances for rain and restrictions late this week.

PBZ WATCHES/WARNINGS/ADVISORIES
PA...None.
OH...None.
WV...None.