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ANZ530 Chesapeake Bay North Of Pooles Island- 732 Pm Edt Wed Oct 4 2023
Tonight..SE winds 5 kt. Waves less than 1 ft. Patchy fog after midnight with vsby 1 to 3 nm.
Thu..SE winds 5 to 10 kt. Waves 1 ft. Patchy fog. Vsby 1 to 3 nm.
Thu night..SE winds 5 to 10 kt. Waves 1 ft.
Fri..SE winds 5 kt. Waves less than 1 ft.
Fri night..SE winds 5 kt. Waves less than 1 ft.
Sat..W winds 10 to 15 kt. Gusts up to 25 kt in the afternoon. Waves 1 to 2 ft. Showers likely.
Sat night..NW winds 15 kt with gusts to 25 kt. Waves 2 ft.
Sun..W winds 10 to 15 kt. Waves 1 to 2 ft.
Mon..SW winds 10 to 15 kt. Waves 1 to 2 ft.

ANZ500 732 Pm Edt Wed Oct 4 2023
Synopsis for the tidal potomac and md portion of the chesapeake bay..
high pressure will gradually move offshore through Thursday. A strong cold front will cross the waters late Friday into Saturday with gusty showers and perhaps a Thunderstorm. High pressure builds from the southwest Sunday while low pressure stalls to the north. Additional weak disturbances pass by early next week. Small craft advisories may be needed Friday night, and will likely be needed behind the front on Saturday and Sunday.

FXUS61 KCTP 050006 AFDCTP

Area Forecast Discussion National Weather Service State College PA 806 PM EDT Wed Oct 4 2023

SYNOPSIS
One more pleasant night with morning valley fog will give way to another warm day on Thursday with increasing clouds. A drastic change in the weather pattern is expected to unfold on Friday as a cold front ushers in periods of rain/showers along with breezy and noticeably cooler temperatures through early next week.

NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
After a stretch of 3+ nights with a persistence forecast, we will finally introduce some changes: (1)better mixing of dry air thanks to a light southeast wind and (2) high clouds overspreading the region. These two factors may lead to fog being a bit less widespread and/or dense compared to the past few mornings. That being said, patchy 1/2-1SM fog is still expected in some locations, especially from the Susq Valley east. High clouds will limit fog potential in the northwest mountains and perhaps Laurel Highlands

High clouds should keep temperatures a few degrees milder tonight in the northwest compared to last night, but a chillier night is expected for the rest of the region with lows in the low to mid 50s.

SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
High clouds will continue to stream overhead during the day on Thursday and thicken up from west to east. After morning fog mixes out, hi-resolution guidance indicates that increasing moisture associated with southeasterly flow off of the Atlantic will lead to the development of some stratus across the southeastern portion of the area after sunrise (mainly south and east of I-81).

As the day progresses and deeper mixing develops, this stratus should transition to stratocumulus with some breaks of filtered sunshine. Cumulus will develop across most of the Commonwealth through the afternoon, which should keep highs a few to several degrees lower than today across most of the area. A few spots may reach the 80 degree mark, but it will be the last 80 degree day for the foreseeable future.

HRRR shows low clouds developing across central and eastern parts of the forecast area tomorrow [Thursday] night due to an increasingly moist SSE llvl/upslope flow. This should put a floor under min temps holding them in the upper 50s to low 60s which is very mild for the overnight period in early October running +15 to +20F above climo. Farther to the west, a band of showers along a leading cold front should reach the western Alleghenies in the 06-12Z Friday period.

Increasing mid and upper level forcing associated with an approaching deep 500mb trough will drive an uptick in shower and potential convective activity over portions of Central PA Friday into early Saturday. Instability is rather weak, but given the height falls and overall increasing synoptic forcing, there will likely be enough instability to support a shallow convective/enhanced rainfall threat. Activity will progress eastward, but the tilting of the trough, generally unidirectional southerly flow, and interaction/absorption of Philippe should be enough to slow the eastward progression enough for there to be local areas of moderate to heavy rainfall. Latest areal averaged rainfall/storm total QPF amounts are around 1" north of US-6 and taper down to 0.25-0.50" in the lower Susquehanna Valley (through midday Saturday). The overall flooding threat remains marginal to low, but can't rule out some minor runoff issues in the more vulnerable low lying/poor drainage areas.

Southerly winds on Friday will shift around to westerly by daybreak Saturday as cooler air begins to pour into the Commonwealth. Temperatures on Saturday morning will remain quite mild across the southeast (low 60s), but fall will be knocking on the door step in western PA where temperatures will drop into the upper 40s.

LONG TERM /SATURDAY THROUGH WEDNESDAY/
GEFS and ECENS indicate the cut off upper low will linger over the Eastern Grt Lks and southern Ontario Saturday through early next week. This scenario supports a high confidence of below normal temperatures along with lake-effect showers and breezy conditions. Latest NBM indicates gusts up to 35-40 mph from the west are possible across the Laurel Highlands and south central Alleghenies on Saturday. Highs on Saturday will range from the low to mid 50s across the higher elevations in the northern mountains and Laurel Highlands to the mid 60s in the Lower Susquehanna Valley - a 20 degree drop from Wednesday to Saturday!

The coldest air since May is expected Sunday into Monday as highs struggle to reach 60 anywhere in Pennsylvania and the higher elevations remain in the 40s. Some higher elevation locations could wake up to their first frost of the season on Monday morning.

For the rest of next week, a persistence forecast is probably the best bet at this point thanks to the upper low swirling directly to the north. Highs in the upper 40s to low 60s will be paired with lows in the upper 30s to mid 40s through the middle of next week. If the upper low drifts a little bit farther to the north toward James Bay as recent model trends indicate, lake effect showers may be less likely as the week progresses and lead to improved sensible weather conditions.

AVIATION /00Z THURSDAY THROUGH MONDAY/
Another in the string of foggy late nights/early morning periods is in store once again tonight (and almost certainly for the last time this week as clouds spread in and the southeasterly breeze increasing).

Mid and high clouds spreading in across the Western part of the state and a light southeasterly breeze will likely hinder much fog formation at TAF sites KJST and KBFD, but fog similar to recent nights (with a few to several hour period of LIFR/VLIFR) is expected throughout the valleys across the Eastern Half of PA.

A light SErly flow will draw moisture in from the ocean, and the morning inversion may trap this moisture and the fog may not completely burn off before the moisture arrives.

The morning surface based inversion should be dissipated/lifted before the mstr arrives in the SE and along the SE- facing slopes of the central mtns. The result could be a low (IFR)
cloud deck lingering for a few hours at LNS and MDT until 14-15Z.

This low cloud deck could expand to the NW, but daytime mixing will make it difficult for the low clouds to stick together and/or to stay low enough to impact flight ops.

A broad storm system is approaching from the west. Showers do not look like they will arrive in the NW before sunset Thurs. The showers should be scattered overnight, and stay confined to the west (KJST and KBFD). The nocturnal inversion will form again overnight and the mstr trapped under it will probably lead to a widespread L\IFR cig. Expect this to not burn off too easily on Fri, but it should as the SHRA from the west will start to move across the rest of the airspace.

Outlook...

Fri...Rain/showers. Restrictions likely. CFROPA Fri night.

Sat-Mon...SHRA and MVFR cigs W. Gusts fm W btwn 20-30 kts.

CLIMATE
A couple of daily high temperature records are within reach at Altoona, Williamsport, and Lancaster on Wednesday 10/4:

Altoona: 83 in 2017 Williamsport: 86 in 1922/1931/1941 Lancaster: 85 in 2007 (POR since 1999)

Bradford could tie or set new record highs for several days this week:

10/2: 79 in 2019 *RECORD TIED 10/3: 78 in 1959 *RECORD BROKEN; 82F at 227pm 10/4: 78 in 2017 *RECORD BROKEN: 82F at 232pm 10/5: 81 in 2007 10/6: 79 in 2013

CTP WATCHES/WARNINGS/ADVISORIES
None.

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Port Deposit
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Wed -- 02:59 AM EDT     3.82 feet High Tide
Wed -- 07:03 AM EDT     Sunrise
Wed -- 11:16 AM EDT     1.27 feet Low Tide
Wed -- 01:06 PM EDT     Moonset
Wed -- 02:47 PM EDT     2.28 feet High Tide
Wed -- 06:42 PM EDT     Sunset
Wed -- 09:36 PM EDT     0.53 feet Low Tide
Wed -- 10:02 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION

Port Deposit, Susquehanna River, Maryland, Tide feet

Havre de Grace
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Wed -- 01:34 AM EDT     2.68 feet High Tide
Wed -- 07:03 AM EDT     Sunrise
Wed -- 09:09 AM EDT     0.32 feet Low Tide
Wed -- 01:05 PM EDT     Moonset
Wed -- 02:32 PM EDT     1.79 feet High Tide
Wed -- 06:42 PM EDT     Sunset
Wed -- 08:22 PM EDT     0.42 feet Low Tide
Wed -- 10:02 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION

Havre de Grace, Susquehanna River, Maryland, Tide feet

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