Mercersburg, PA Marine Weather and Tide Forecast
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Marine Weather and Tide Forecast for Mercersburg, PA

June 19, 2024 12:35 PM EDT (16:35 UTC) Change Location
Sunrise 5:41 AM   Sunset 8:43 PM
Moonrise 5:50 PM   Moonset 2:26 AM 
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NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION.

Marine Forecasts
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ANZ538 Patapsco River Including Baltimore Harbor- 1038 Am Edt Wed Jun 19 2024

Rest of today - SE winds 10 kt. Waves 1 ft.

Tonight - S winds 5 to 10 kt. Waves 1 ft.

Thu - S winds 5 to 10 kt. Waves 1 ft or less.

Thu night - S winds 5 to 10 kt. Waves 1 ft.

Fri - S winds 5 to 10 kt. Waves 1 ft.

Fri night - S winds 5 to 10 kt. Waves 1 ft.

Sat - S winds 5 to 10 kt. Waves 1 ft or less.

Sun - SW winds 5 to 10 kt. Waves 1 ft. A chance of showers and tstms.
winds and waves higher and visibilities lower in and near tstms.

ANZ500 1038 Am Edt Wed Jun 19 2024

Synopsis for the tidal potomac and md portion of the chesapeake bay -
high pressure will remain anchored offshore through the week. Winds will remain light with a southerly component through the week.


7 Day Forecast for Marine Location Near Mercersburg, PA
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Area Discussion for - State College, PA
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FXUS61 KCTP 191515 AFDCTP

Area Forecast Discussion National Weather Service State College PA 1115 AM EDT Wed Jun 19 2024

SYNOPSIS
The center of a subtropical upper level high over Pennsylvania will sink southward over the next few days. A weak cold front will approach and stall out over the region Friday and Saturday. A more significant cold front is likely to push through Sunday night or early Monday.

NEAR TERM /THROUGH TONIGHT/
11 AM EDT Update:

Forecast pretty much on track with some minor adjustments to clouds and a slight upward adjustment to POPs over the far NW zones based on high res ensembles and their members that indicate a fairly high probability for SHRA/Sctd TSRA forming after 19Z. This part of our CWA will also be within an area of weak mesoscale UVVEL linked to the thermally direct cell of a weak mid/upr level shortwave lifting NE across the Lower Glakes and along the axis of highest PWAT air of around 2.00 inches.
Will have to keep a close eye on the potential for some strong to potentially SVR and training cells on an axis from near KGKJ to KJHW and KOLE. Locations along this axis have 1 hour Flash Flood Guidance values reduced to between 1.25 and 1.5 inches from Tuesday evening's TSRA and will be susceptible to flash flooding from any training cells.

Pertinent parts of the previous discussion follow.

The lack of nighttime cooling/recovery and high daytime temps continue to warrant a heat advy even if we stay just below 100F today. The duration (many days) of the heat wave weighs heavily in the WWA decisions, too. High clouds today will be thickest over the west. They will make little difference in max temps today as the 8H temps will be higher in the NW than SE. The deepest mixing today will be a rather homogeneous 5kft across the CWA That puts maxes in the u80s on the ridge tops and l90s in the valleys - very close to Tues.

Convection will build again in the middle of the day, but the storms will be more over the nrn tier due to the upper heights and capping being better over the srn half of the area. PWATs remain high (>1.5") across the N, so heavy rain is possible out of any of those storms. Pulse storms with little motion are likely to be the mode today with the hodograph looking more like an ink blot than a smooth line or curve. As with yesterday, CAPE could get >2000J/kg in the nrn tier, and that could make a wet microburst out of an isolated cell or two.

Expect tonight to be another muggy one with convection dying down before midnight. We'll leave a small PoP across the north after midnight as the ring of fire flattens out and any transitory cells could travel along the lakeshore and into wrn NY. Mins of 65-70F will be a little lower than recent days because some subsidence under the big upper high could inch dewpoints down into the lower 60s in spots overnight. The higher dewpoints will be stubborn over the nrn tier due to earlier rainfall.

SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/
Heights fall slightly across the nrn tier as the big high aloft slides a little to the south. That could allow the daily pop-up storms to grow a little taller and have a higher potential for making wind damage. SPC Day2 puts areas N of I-80 into the MRGL risk and far NE (Tioga/Sullivan Cos) into the SLGT risk category. Capping should keep things less active across srn PA on Thurs. Persistence will be the best forecast for maxes, and the dewpoints seem to recover just fine from any lowered numbers in the morning, getting back into the u60s almost everywhere and around 70F in the N for the middle of the day.

Heights lower just a little more on Friday, and a weakness in the sfc pressure field develops over the nrn tier. How far S the weak/diffuse front will make it on Fri will help determine the eventual coverage of storms. Will go with a 40-50pct coverage over the nrn half of the CWA in the aftn and evening Fri. Again, one or two of these storms could produce a damaging wind gust. There should be a little bit of movement (W-E) to the storms on Thursday and a little bit more on Friday. But, the shear is still pretty weak.

Again, we'll hold onto the heat advy for both Thurs and Friday.
Friday does look a little more muggy and the heat index values will be a couple of degrees higher than Thursday (and Wed).

LONG TERM /FRIDAY THROUGH TUESDAY/
Did go ahead and stretch the heat advisory out into Saturday for everyone. Latest heat index fcst nums look 2-3F higher Sat than Fri. Passed on extending it into Sunday, since the NW looks to be a little cooler/lower (HIs in the 80s) on Sunday. The SE half looks like they'll get back near 100 HI again on Sunday.

Prev...
Medium range guidance indicates PA will remain under a low amplitude upper level ridge with a strong surface high parked near Bermuda, resulting in a continuation of the heat and humidity. Ring of fire convection looks likely Saturday, especially along the northern tier of the state. Falling heights ahead of an upstream trough over the Grt Lks is likely to result in at least scattered PM convection Sunday.

Current 2m and 850mb temps plumes indicate some of the hottest weather of this stretch could occur next weekend, so may need to extend the heat advisory, which currently only lasts through Friday.

Most locations should see a round of showers/tsra Sunday PM into Monday AM associated with the passage of the shortwave trough and attendant cold front. Behind this feature, expect a return to fair and more seasonable conditions later Monday into Tuesday, as surface ridging and drier air works in from the Grt Lks.

AVIATION /15Z WEDNESDAY THROUGH SUNDAY/
The highest chance of a shower or storm will be a bit further north and west today, mainly at BFD and points west where the axis of deepest moisture resides and some larger scale lift will be provided by a weak upper level disturbance moving NE across Lake Erie.

Dewpoints expected to drop off a bit today, which supports the lower chance of showers and storms later today.

There could be some fog late tonight, mainly near BFD, but that depends if it rains there later this afternoon.

Not much change for tonight right into Friday.

There could be a strong storm Thursday into Friday, mainly across the northern portion of central PA, as the front sags to the south.

Outlook...

Thu-Sun...Predominantly VFR, with continued heat and iso TSRA.
Density altitude concerns possible.

CLIMATE
A period of warmer than average temperatures is expected across much of central Pennsylvania through the end of the week, with record high temperatures at multiple cities being challenged every day through Saturday.

Two records were either set or tied for sites on Tuesday: * A record high temperature of 92 degrees was set at Altoona yesterday, which tied the old record of 92 degrees set back in 1994.
* A record high temperature of 90 degrees was set at Bradford yesterday. This broke the e old record of 87 degrees set back in 1993.

The record high temperatures for some sites across central PA that could be challenged are outlined below:

Jun 19 Jun 20 Jun 21

Harrisburg 98/1994 98/1931 98/1923 Williamsport 96/1929 101/1923 97/1933 State College 94/1931 94/1953 94/1988

Highest Max Temperatures for Central Pennsylvania Observing sites for June (date of occurrence is in parentheses:

State College 96 in 1952 (26th) and 1933 (29th)
Harrisburg 100 in 1966 (27th), 1952 (26th), and 1934 (29th)
Williamsport 104 in 1925 (5th)
Altoona 97 in 1971 (28th) and 1953 (21st)
Bradford 93 in 2022 (22nd)

Longest run of consecutive days with max temp >=90 in June:

State College 6 (24-29th 1966)
Harrisburg 10* (19-28th 1943)
Williamsport 9 (18-26th 1923)
Altoona 8 (13-20th 1994)
Bradford 0 (has not occurred since POR started at site in 1957)

*Harrisburg had a run of 11 days with temperatures greater than 90 degrees that started on 26th and ended on July 6th in 1901.

CTP WATCHES/WARNINGS/ADVISORIES
Heat Advisory until 8 PM EDT Saturday for PAZ004>006-010>012- 017>019-024>028-033>037-041-042-045-046-049>053-056>059- 063>066.




Weather Reporting Stations
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Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisSkyWeatherAirDewPtRHinHg
KHGR HAGERSTOWN RGNLRICHARD A HENSON FLD,MD 12 sm42 minvar 0510 smClear86°F66°F52%30.35
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Wind History graph: HGR
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Tide / Current for Chain Bridge, D.C.
   
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Chain Bridge
Click for Map
Wed -- 12:56 AM EDT     0.52 feet Low Tide
Wed -- 03:25 AM EDT     Moonset
Wed -- 05:42 AM EDT     Sunrise
Wed -- 07:13 AM EDT     3.31 feet High Tide
Wed -- 02:17 PM EDT     0.46 feet Low Tide
Wed -- 06:43 PM EDT     Moonrise
Wed -- 07:54 PM EDT     2.70 feet High Tide
Wed -- 08:37 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

Chain Bridge, D.C., Tide feet
12
am
0.6
1
am
0.5
2
am
0.7
3
am
1.1
4
am
1.9
5
am
2.6
6
am
3.1
7
am
3.3
8
am
3.2
9
am
2.8
10
am
2.2
11
am
1.6
12
pm
1.1
1
pm
0.7
2
pm
0.5
3
pm
0.6
4
pm
1
5
pm
1.7
6
pm
2.2
7
pm
2.6
8
pm
2.7
9
pm
2.5
10
pm
2
11
pm
1.4


Tide / Current for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Wed -- 12:51 AM EDT     0.52 feet Low Tide
Wed -- 03:25 AM EDT     Moonset
Wed -- 05:42 AM EDT     Sunrise
Wed -- 07:08 AM EDT     3.31 feet High Tide
Wed -- 02:12 PM EDT     0.46 feet Low Tide
Wed -- 06:43 PM EDT     Moonrise
Wed -- 07:49 PM EDT     2.70 feet High Tide
Wed -- 08:36 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

Chain Bridge, one mile below, D.C., Tide feet
12
am
0.6
1
am
0.5
2
am
0.7
3
am
1.2
4
am
2
5
am
2.7
6
am
3.1
7
am
3.3
8
am
3.2
9
am
2.7
10
am
2.1
11
am
1.6
12
pm
1.1
1
pm
0.7
2
pm
0.5
3
pm
0.6
4
pm
1.1
5
pm
1.7
6
pm
2.3
7
pm
2.6
8
pm
2.7
9
pm
2.4
10
pm
1.9
11
pm
1.3


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