Saturday, July4, 2020
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Marine Weather and Tides
Kemps Mill, MD

Version 3.4
NOTICE
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.

Sunrise 5:47AMSunset 8:43PM Saturday July 4, 2020 2:15 PM EDT (18:15 UTC) Moonrise 7:35PMMoonset 4:04AM Illumination 99% Phase: Waxing Gibbous; Moon at 14 days in cycle
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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ANZ535 Tidal Potomac From Key Bridge To Indian Head- 155 Pm Edt Sat Jul 4 2020
This afternoon..NE winds 5 kt. Waves less than 1 ft. A chance of showers and tstms.
Tonight..S winds around 5 kt. Waves 1 ft. A chance of showers and tstms.
Sun..S winds around 5 kt. Waves 1 ft. A chance of showers and tstms.
Sun night..S winds 5 kt. Waves less than 1 ft.
Mon..S winds around 5 kt. Waves 1 ft. A chance of showers and tstms.
Mon night..S winds around 5 kt. Waves 1 ft. A chance of showers and tstms.
Tue..S winds around 5 kt. Waves 1 ft. A chance of showers and tstms through the night.
Wed..S winds around 5 kt. Waves 1 ft. A chance of showers and tstms. Winds and waves higher and visibilities lower in and near tstms.
ANZ500 155 Pm Edt Sat Jul 4 2020
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A weak backdoor boundary will stall southwest of the waters today and it will weaken tonight into Sunday. High pressure over the atlantic will control the weather pattern for the early and middle portion of next week. Low pressure will pass by to the south during this time.


7 Day Forecast for Marine Location Near Kemps Mill, MD
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location: 39.63, -77.79     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 041328 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 928 AM EDT Sat Jul 4 2020

SYNOPSIS. A weak backdoor boundary will stall over the region today before dissipating tonight into Sunday. High pressure will build overhead at the surface and aloft for the early and middle portions of next week, bringing hot and humid conditions to the area.

NEAR TERM /THROUGH TONIGHT/. Current temperatures across the region generally running a few degrees warmer (low to mid 80s already) than previously forecast east of the Blue Ridge to along the I-95 corridor. Generally think highs today stay close to the previous forecast though, given data from the 12z IAD sounding. Maybe we get another degree or so, so have slightly increased the highs, given the latest trends. Some lower clouds moving into our northeastern areas, but those are beginning to, and should continue to, scatter out and lift as we quickly heat up through the morning. Dew points across the region are right in line with the previous forecast, with values in the upper 60s to low 70s.

PREVIOUS DISCUSSION: Elsewhere, ample sunshine is expected this morning. In response to this sunshine, temperatures will quickly climb through 80s, before eventually topping out in the low 90s. It will also feel humid, with dewpoints in the mid 60s to low 70s. Heat index values will max out in the low-mid 90s in most locations, with some upper 90s possible down toward Fredericksburg.

The main forecast concern today will be when and where thunderstorms form. A weak shortwave embedded in northwesterly flow aloft will drop into the area this afternoon, moving through around peak heating. At the surface, the aforementioned very weak backdoor front will gradually move through the area today. There won't be much of a discernible temperature or moisture difference across the boundary, but there should be at least a little low-level convergence along the boundary. There are also some signs that a weak pressure trough may develop over the higher terrain. Forecast model soundings show a lot of dry air in the mid-levels, as well as hints of a weak subsidence inversion around 600 mb. As a result, it is expected that storms will have a hard time initiating away from the two previously mentioned boundaries. Have focused in higher PoPs along these boundaries, with scattered coverage expected along the boundaries and isolated coverage elsewhere. During the early-mid afternoon hours, the composite backdoor front/bay breeze will be aligned along the I-95 corridor. Storms are expected to form during the early to mid-afternoon hours, with the best chances for storms residing along the boundary extending from DC southward to Fredericksburg. Storms should also form during the mid afternoon hours over the higher terrain. These storms may eventually progress southeastward within the northwesterly flow aloft along a corridor stretching roughly from Allegany County to Orange/Culpeper Counties. Most of the thunderstorm activity is expected to die down by nightfall, given loss of daytime heating and the progression of the mid-level shortwave off to our south (placing us within a zone of subsidence aloft). The exception may be down near CHO, where showers and storms could potentially linger a bit into the overnight hours.

The environment storms will go up in today will be characterized by MLCAPE values between 1000-2000 J/kg and 0-6 km shear values of 20- 25 knots. As a result, loosely organized multicells could be possible. With lots of mid-level dry air in place, storms may entrain a lot of dry air, leading to weaker updrafts than one might expect with 1000-2000 J/kg of MLCAPE. However, if storms are able to grow tall and punch through that mid-level dry air, that same mid- level dry air will lend itself to high levels of DCAPE. Soundings from multiple models show DCAPE values of around 1000-1400 J/kg this afternoon across the area. So if strong updrafts do occur, they will have the potential to produce localized strong downbursts of wind.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/. High pressure aloft will build toward the area Sunday through Monday night while surface high pressure builds over the Atlantic. A light southerly flow along with rising heights will allow for hot and humid conditions with max temps in the 90s both days and low temperatures in the 60s and 70s.

The heat and humidity along with weak lift from a pressure trough, bay/river breezes, and terrain circulation may lead to a few showers and thunderstorms during the afternoon and evening hours each day. Coverage should be isolated to scattered since the lifting mechanisms will be weak, but locally gusty winds and heavy rainfall are possible in any storms that do develop since there will be moderate amounts of instability (both CAPE and DCAPE).

LONG TERM /TUESDAY THROUGH FRIDAY/. Upper-level high pressure will continue to build toward the area Tuesday before settling overhead Wednesday through Friday. Most guidance indicates that a cutoff upper-level low will develop to the south Tuesday, and strengthen as it moves offshore Wednesday through Friday. The details of exactly where the upper-level low will be remain uncertain at this time, but most guidance suggests that it will remain to our south. If this occurs, then thunderstorms will remain isolated to scattered and confined mainly to the afternoon and evening hours. However, should the upper-level low track farther north, then more widespread showers and thunderstorms would occur. Will continue to lead toward the first scenario based on the latest guidance, which means more hot and humid conditions are likely and convection will be more isolated or scattered.

AVIATION /14Z SATURDAY THROUGH WEDNESDAY/. Low clouds (around 1500 foot CIGs) trying to work their way into northeastern MD now. Maintainig scattered clouds at that level at MTN at 14z, as it does seem they will make it there. However, as previously discussed, they should break up and begin to lift. Already evident on satellite imagery is a trend for them scattering out, so would expect this to continue. At worst, maybe a brief broken period of MVFR CIGs, but don't have any condience to put that in the TAF at this point.

Any low clouds that move in should rise and scatter into a cumulus deck by around midday. Prevailing VFR conditions are expected at all terminals this afternoon. Temporary drops to sub-VFR conditions will be possible in any thunderstorms that form this afternoon. A stray shower or thunderstorm can't be ruled at any of the terminals, but DCA and MRB have the greatest chance to see a thunderstorm. In terms of timing, think that most of the activity will occur between 18 and 22z. Chances may linger a bit later into the evening and potentially even into the overnight hours at CHO. Winds will start out light out of the north , before gradually switching around to light out of the east during the afternoon and evening hours.

Skies are expected to clear tonight across most of the area. Winds will shift around to light out of the south, but may eventually go calm at MRB and CHO. With clear skies and calm winds, fog may be possible overnight tonight at MRB. If skies clear out at CHO, fog may be possible there as well. If winds were to go calm, fog could also be possible at IAD, but there seems to be a lesser chance of that occurring.

Hot and humid conditions are expected Sunday through Wednesday along with chances for showers and thunderstorms during the afternoon and evening hours. Patchy fog is possible during the late night and early morning hours each day as well.

MARINE. Light winds are expected over the waters today through tonight. They will start out northerly, then gradually turn around to easterly over the course of the daylight hours, then southerly to eventually even soConfidence in this occurring remains low, so just have a scattered in the TAF at BWI and MTN for now. We will continue to assess this potential through the remainder of the night.uthwesterly overnight. Isolated thunderstorms are expected this afternoon over the waters, and could lead to the issuance of Special Marine Warnings.

A southerly gradient wind should remain below SCA criteria most of the time Sunday through Wednesday. However, isolated to scattered thunderstorms are possible during the afternoon and evening hours each day, and locally gusty winds are possible in any thunderstorm that develops.

TIDES/COASTAL FLOODING. A light southerly flow will develop tonight into Sunday, and it will persist through early next week. This will cause water levels to be elevated. Minor flooding is possible at sensitive areas, beginning with the high tide cycle later tonight and continuing into early next week. However, confidence is low because the flow will be light.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . None. VA . None. WV . None. MARINE . None.

SYNOPSIS . BJL NEAR TERM . CJL/KJP SHORT TERM . BJL LONG TERM . BJL AVIATION . BJL/CJL/KJP MARINE . BJL/KJP TIDES/COASTAL FLOODING . BJL


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 66 mi46 min SE 1.9 G 5.1 88°F 84°F1013.1 hPa
BLTM2 - 8574680 - Baltimore, MD 69 mi46 min S 8 G 11 81°F 77°F1013 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 73 mi46 min SE 6 G 8 81°F 1013.5 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Hagerstown, Washington County Regional Airport, MD6 mi23 minN 710.00 miA Few Clouds92°F59°F33%1013.8 hPa
Eastern WV Regional Airport/Shepherd Field, WV18 mi23 minVar 310.00 miA Few Clouds90°F66°F45%1012.8 hPa

Link to 5 minute data for KHGR

Wind History from HGR (wind in knots)
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Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
Click for Map
Sat -- 02:39 AM EDT     0.20 feet Low Tide
Sat -- 05:03 AM EDT     Moonset
Sat -- 05:48 AM EDT     Sunrise
Sat -- 08:27 AM EDT     3.68 feet High Tide
Sat -- 03:38 PM EDT     -0.01 feet Low Tide
Sat -- 08:29 PM EDT     Moonrise
Sat -- 08:37 PM EDT     Sunset
Sat -- 09:04 PM EDT     3.06 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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1.10.60.30.20.61.52.53.23.63.63.12.51.81.20.60.100.51.42.22.83.12.82.3

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Sat -- 02:34 AM EDT     0.20 feet Low Tide
Sat -- 05:03 AM EDT     Moonset
Sat -- 05:48 AM EDT     Sunrise
Sat -- 08:22 AM EDT     3.68 feet High Tide
Sat -- 03:33 PM EDT     -0.01 feet Low Tide
Sat -- 08:29 PM EDT     Moonrise
Sat -- 08:37 PM EDT     Sunset
Sat -- 08:59 PM EDT     3.06 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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10.60.30.20.71.62.63.33.73.63.12.41.81.20.60.100.61.52.32.83.12.82.2

Weather Map
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wmap_A
GEOS Local Image of    EDIT
NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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Wind Forecast for Baltimore, MD/Washington (14,3,4,5)
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Ground Weather Radar Station Sterling, VA
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The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerous of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.