Thursday, July29, 2021
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Marine Weather and Tides
Halfway, MD

Version 3.4
NOTICE
3/30/2021 -- ANZ330 has been split into ANZ331 and ANZ332. Click EDIT in Marine Forecast and select your new zone.
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.

Sunrise 6:06AMSunset 8:28PM Thursday July 29, 2021 4:09 AM EDT (08:09 UTC) Moonrise 10:49PMMoonset 10:52AM Illumination 75% Phase: Waning Gibbous; Moon at 20 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- 325 Am Edt Thu Jul 29 2021
.small craft advisory in effect from Friday morning through Friday afternoon...
Rest of the overnight..SE winds 5 kt. Waves less than 1 ft. A slight chance of showers and tstms. Patchy fog.
Today..S winds around 5 kt. Waves 1 ft. A chance of showers. Patchy fog.
Tonight..SW winds 5 kt. Waves less than 1 ft. A chance of showers and tstms.
Fri..NW winds 5 to 10 kt with gusts to 20 kt. Waves 1 ft.
Fri night..N winds 5 to 10 kt. Gusts up to 20 kt in the evening. Waves 1 ft.
Sat..NW winds 5 kt. Waves less than 1 ft.
Sat night..S winds around 5 kt. Waves 1 ft. A chance of showers.
Sun..W winds around 5 kt. Waves 1 ft. Scattered showers. A chance of tstms through the night.
Mon..NE winds around 5 kt. Waves 1 ft. Winds and waves higher and visibilities lower in and near tstms.
ANZ500 325 Am Edt Thu Jul 29 2021
Synopsis for the tidal potomac and md portion of the chesapeake bay.. A weak front will waffle across the mid atlantic through Thursday morning. A stronger cold front will cross through the area by Thursday night. High pressure will build in for Friday and Saturday.


7 Day Forecast for Marine Location Near Halfway, MD
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location: 39.62, -77.79     debug


Area Discussion for - Baltimore, MD/Washington
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FXUS61 KLWX 290048 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 848 PM EDT Wed Jul 28 2021

SYNOPSIS. A cold front will approach the area tomorrow into tomorrow night. High pressure will build in for Friday into this weekend, bringing drier and cooler conditions. Another system may impact the area early next week.

NEAR TERM /THROUGH THURSDAY/. 8:45 PM UPDATE: Current radar imagery depicts widely scattered showers and thunderstorms across northern VA and into northern and western MD. Also notable in radar imagery has been the Bay Breeze, which has made it well into northern VA at this time. Storms have struggled to get going in these regions however, owing to weak mid-level lapse rates and abundant dry air aloft. However, the surface level dry air has allowed for some decent wind gusts even out of relatively weak showers (up to 30 mph or so). What this has also done is allowed for plenty of residual outflow boundaries to be lying around. Could see those interact with the Bay Breeze and locally enhance convection. For now, seems like that is becoming less likely as we get further past sunset. The 00z IAD RAOB continued to show 1000 J/kg or so of MLCAPE, so there is still at least some instability around. RAP mesoanalysis even shows an increase in MLCAPE through the next several hours, albeit slight. So, can't completely rule out a rogue stronger storm, but for now at least, seems as though the dry air and weak lapse rates are winning out. Per the latest RAP mesoanalysis however, the region does lie within the left-exit region of an approaching upper jet. So, activity may last into the overnight hours as ascent attendant to the upper level jet streak spreads over our area. Recent runs of the HRRR have this type of scenario playing out, with storms lasting until after midnight. Storms should eventually dissipate much later tonight, giving way to partly to mostly cloudy skies late tonight. Lows overnight will be in the upper 60s to lower 70s.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/. Tomorrow's forecast is a challenging one locally. A very strong MCS is expected to develop over the Upper Midwest/Lower Great Lakes this evening into tonight. This MCS should eventually weaken overnight as it moves into a lower CAPE environment over the Ohio Valley. A remnant outflow boundary/convective debris will spread over at least northern portions of the area tomorrow morning, with a connectively enhanced speed max in the 700-500 hPa layer following immediately in its wake. There is a wide spread of possible solutions in model guidance with respect to subsequent development of storms across our area tomorrow. Some solutions try to refine storms along the leading edge of the remnant outflow as it sweeps eastward across the area. Other solutions keep this activity suppressed. Other solutions fire additional storms in the wake of the convective debris. Some solutions do not.

The environment in the wake of the leftover convective debris as the convectively enhanced speed max moves overhead is concerning. Models such as the NAM and Euro spread a belt of 40-50 knot flow in the 700-500 hPa layer over the northern half of our CWA by around peak heating. If we were to destabilize and storms were to form in that type of environment, the potential is there for a significant severe weather event, with very high winds, large hail, and tornadoes all possible. However, there's considerable disagreement amongst the various models as to if and where storms will form in the wake of what's left of today's Upper Midwest system. Strong MCSs are often not handled well by both the CAMs and global guidance, and any system that forms today will have a strong influence on our weather for tomorrow. As a result, confidence in the evolution of storms tomorrow remains low. Confidence should gradually increase over time as today's system gets going and becomes better handled by model guidance. We'll continue to refine our forecast for what is a low confidence, but also potentially high impact severe weather event tomorrow.

A cold front will press through the area tomorrow night and high pressure will build into the area on Friday. Much drier air will work into the area on northerly flow behind the cold front. Temperatures will remain warm with highs in the high 80s, but dewpoints will drop into the 50s, making it feel a bit more comfortable.

LONG TERM /SATURDAY THROUGH WEDNESDAY/. Cooler temperatures than recent days and dry conditions with high pressure moving overhead Saturday. High temperatures reaching the middle 80s. The high shifts eastward to allow for a return flow to bring in more moisture and warmth from the south Saturday night into Sunday.

A couple of showers could develop in parts of the region Saturday night with a chance of additional showers and a thunderstorm or two Sunday with a cold front approaching and moving through the region. Sunday's highs will reach the middle to upper 80s.

A few lingering showers are possible Sunday night into Monday with a bout of dry conditions to follow later Monday afternoon and Monday night. Highs Monday in the middle 80s.

Tuesday appears to have some modest uncertainties as we could either be looking at dry conditions and temperatures in the middle to upper 80s or periods of rain with embedded thunderstorms and temperatures in the lower 80s. The first would be if high pressure hovers over us as a weak front stays well to our northwest and a possible coastal low pressure stays well to our southeast. The latter would be if the coastal low wins out and moves northeast up the mid-Atlantic seaboard. For now, we will keep an isolated shower or two for Tuesday mainly across the southeastern half of our region.

AVIATION /01Z THURSDAY THROUGH MONDAY/. A few widely scattered showers and storms in the area tonight, and will likely continue into the overnight hours. Have added VCTS on many terminals (not CHO though). Don't think we see much in the way of severe weather, but could see brief restrictions if any of these wander over the terminals. For now though, most of the terminals remain dry.

Prevailing VFR conditions are expected through Friday. Thunderstorms will be possible at the terminals Thursday afternoon, potentially leading to brief restrictions. The evolution of storms on Thursday is much more uncertain, but have decided to at least add some VCTS to the northern terminals (so just excluding CHO) during the afternoon. If thunderstorms were to occur tomorrow, they could potentially be very strong, with very high winds and hail possible. However, it's also possible that storms avoid the terminals. For now, wanted to add in an inclusion of VCTS just to provide extra awareness to the potential threat tomorrow.

Despite an isolated shower Saturday night and a few showers and a thunderstorm possible Sunday, expect VFR conditions. Winds northwest becoming south 5 to 10 knots Saturday into Saturday night. Winds southwest becoming northwest around 10 knots with higher gusts Sunday.

MARINE. Sub-SCA conditions are expected in light northerly flow today. Winds will turn southerly tomorrow and may approach SCA levels briefly in southerly channeling tomorrow afternoon. However, confidence in that occurring was too low to issue an SCA at the moment. SMWs will be possible in association with any thunderstorms that move over the waters both this afternoon and tomorrow afternoon. The winds in any thunderstorms tomorrow afternoon could be very strong, with over 50 knots possible in the strongest cells. Additionally, in the wake of that frontal boundary, winds are expected to exceed SCA criteria, so have added an SCA starting late tomorrow night, which will continue through at least Friday morning.

No marine hazards expected Saturday through Sunday night. Winds northwest becoming south around 10 knots Saturday and Saturday night. Winds generally southwest shifting late to northwest at 10 to 15 knots Sunday and Sunday night.

TIDES/COASTAL FLOODING. Southerly flow ahead of an approaching cold front will likely bring tides up to action stage over the next couple days. Minor flooding may be possible at the most sensitive sites like Annapolis. Northwest flow behind the front by Friday should allow anomalies to drop.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . None. VA . None. WV . None. MARINE . Small Craft Advisory from 10 PM Thursday to 6 AM EDT Friday for ANZ534-537-542-543.

SYNOPSIS . KJP NEAR TERM . CJL SHORT TERM . KJP LONG TERM . KLW AVIATION . KLW/CJL/KJP MARINE . KLW/CJL/KJP TIDES/COASTAL FLOODING . RCM/CPB/ADS


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 66 mi51 min S 2.9 G 5.1 75°F 84°F1015 hPa
BLTM2 - 8574680 - Baltimore, MD 69 mi51 min SSW 2.9 G 5.1 76°F 84°F1014.9 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 72 mi51 min SSE 5.1 G 6 76°F 1015.1 hPa

Wind History for Washington, DC
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Hagerstown, Washington County Regional Airport, MD7 mi76 minN 07.00 miFair72°F67°F84%1015.8 hPa
Eastern WV Regional Airport/Shepherd Field, WV18 mi76 minN 010.00 miA Few Clouds69°F66°F90%1014.4 hPa

Link to 5 minute data for KHGR

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Last 24hrE3E4CalmSE3NW5NW5W5NW5N9NE9
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1 day agoCalmCalmE4Calm33NW7N6NW64S5N5W6NW6NW7NW4NW3CalmS3SW5S3SE3NE3Calm
2 days agoS3CalmSE5CalmCalmW5NW544W5E7NE7NE5NE5E4SE3SE4CalmS7SW4CalmE4E4NE4

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
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Thu -- 01:11 AM EDT     3.21 feet High Tide
Thu -- 06:06 AM EDT     Sunrise
Thu -- 07:51 AM EDT     0.40 feet Low Tide
Thu -- 11:49 AM EDT     Moonset
Thu -- 01:30 PM EDT     3.09 feet High Tide
Thu -- 08:05 PM EDT     0.28 feet Low Tide
Thu -- 08:22 PM EDT     Sunset
Thu -- 11:46 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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33.23.12.621.40.90.50.40.71.42.22.73.132.72.11.40.90.50.30.51.11.9

Tide / Current Tables for Chain Bridge, one mile below, D.C.
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Chain Bridge
Click for Map
Thu -- 01:06 AM EDT     3.21 feet High Tide
Thu -- 06:06 AM EDT     Sunrise
Thu -- 07:46 AM EDT     0.40 feet Low Tide
Thu -- 11:49 AM EDT     Moonset
Thu -- 01:25 PM EDT     3.09 feet High Tide
Thu -- 08:00 PM EDT     0.28 feet Low Tide
Thu -- 08:22 PM EDT     Sunset
Thu -- 11:46 PM EDT     Moonrise
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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33.232.51.91.30.90.50.40.71.52.22.83.132.621.40.80.40.30.51.12

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