Thursday, December12, 2019
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Marine Weather and Tides
Kemps Mill, MD

Version 3.4
NOTICE
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.
6/2/2019. Many thanks to a user for reporting an error on one of the Edit pages. The switch to PHP 7.2 caused many pages that previously worked to quit working. I fixed many but I still depend on users to report ones I missed. Please report errors HERE or send an email to me at L-36.com. Allen

Sunrise 7:20AMSunset 4:48PM Thursday December 12, 2019 2:40 PM EST (19:40 UTC) Moonrise 5:24PMMoonset 7:39AM Illumination 99% Phase: Waning Gibbous; Moon at 16 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- 1238 Pm Est Thu Dec 12 2019
This afternoon..E winds 5 kt. Waves less than 1 ft.
Tonight..N winds around 5 kt. Waves 1 ft or less.
Fri..NE winds around 5 kt. Waves 1 ft. Rain likely or a chance of freezing rain.
Fri night..N winds around 5 kt. Waves 1 ft. Rain.
Sat..SW winds around 5 kt. Waves 1 ft. Showers likely.
Sat night..W winds 5 to 10 kt. Waves 1 ft. A chance of showers.
Sun..NW winds 5 to 10 kt. Waves 1 ft.
Mon..S winds around 5 kt. Waves 1 ft. A chance of rain or snow through the day, then rain or snow likely through the night.
ANZ500 1238 Pm Est Thu Dec 12 2019
Synopsis for the tidal potomac and md portion of the chesapeake bay.. High pressure over the region will shift offshore today. A low pressure system developing over the northern gulf of mexico will move northeastward toward the region Friday into Saturday. Small craft advisories may be needed Saturday through Sunday morning.


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 121515 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1015 AM EST Thu Dec 12 2019

SYNOPSIS. High pressure over the region this morning will head off the coast by tonight. Low pressure will start developing along the Gulf Coast tonight and then head northward up the East Coast Friday and Saturday. High pressure will return briefly on Sunday before another system potentially affects the region Monday and Monday night. Cold high pressure will then follow for the middle of next week.

NEAR TERM /THROUGH FRIDAY/. Strong high pressure (1040mb) sits just northwest of the region presently and will continue sliding east toward the coast throughout the day. Winds will be light and skies mostly clear today. After a cold start, the weak winter sun will only allow modest warming, with most places failing to reach 40 degrees today. Not bitterly cold for mid-December, but below normal for sure. Winds will be light, however, and with the sunshine, it won't feel as bad as it could.

PREVIOUS DISCUSSION: Tonight will start out mostly clear, allowing for some radiational cooling. However, developing system to the south will quickly send some warm advection our way, resulting in increasing clouds. Guidance almost universally has precipitation overspreading the I-64 corridor by 7 AM, and many models have precip approaching DC itself by then. Have sped up timing of precip arrival in the forecast somewhat, but not as far as latest guidance would suggest. That said, it remains a known bias for models to be too slow with warm advection precip, so remain concerned that precip may arrive sooner than forecast.

The reason this is a concern, of course, is that with warm air aloft but cold surface temps, the most likely precip type before and just after dawn is freezing rain. Have added ice accumulations, though relatively modest ones, extending into the DC western suburbs and north up the I-81 corridor, but would not be shocked to see ice edge even closer to DC itself if precip arrives as early as some guidance suggests. That said, the initial burst of precip should be fairly light, so not expecting any winter storm warning type stuff here . a tenth of an inch is probably the most anyone will get. However, the time of day makes this highly impactful, being that we will likely have cold road surfaces and we will be entering rush hour. All that having been said, its still late second period, so opted to wait a bit longer before issuing any winter weather headlines.

The light rain may actually end for a time in the afternoon Friday, as the initial burst of warm advection wanes. Highs east of the Blue Ridge should reach the lower 40s with the flow turning easterly, but west of the Blue Ridge, temps likely struggle to get much above freezing.

SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/. The main low pressure system will move north across the region Friday night. By this time, expect nearly everyone if not everyone to have risen above freezing, so rain is expected, and its possible it could be moderate to borderline heavy for a time. That said, timing and placement are still uncertain, and it hasn't been excessively wet lately, so don't currently expect any hydro issues.

Low pushes north on Saturday, and rain should taper to showers. After cold advection starts in the afternoon, upslope showers will develop and change to snow in the higher elevations by evening. However, only light accumulations are expected, with no winter weather advisories for snow currently anticipated. Further east, Saturday afternoon and evening will be slowly drying out, with relatively mild temps near 50 in the afternoon dropping into the 30s at night.

LONG TERM /SUNDAY THROUGH WEDNESDAY/. As a potent low pressure system over New England departs to the northeast into the eastern Canadian Maritimes Sunday, a broad area of high pressure over the Midwest U.S. will quickly build into the region late Sunday into Sunday night. A few inches of upslope snow in the Potomac Highlands should come to an end around midday Sunday with the building high pressure. A dry and cold period will be brief late Sunday and Sunday night.

The next low pressure system will approach from the southwest late Sunday night through Monday night. As of now, there is a noticeable discrepancy or difference between the GFS and Euro deterministic models. The GFS makes the track of the low from the middle Mississippi Valley to the Lower Great Lakes. The Euro deterministic model makes the track of the low from the Tennessee Valley to the Delmarva Peninsula and then offshore. The GFS is the warmer solution. One thing to note that could be the determining factor as to whether we see accumulating snowfall or a mix of snow, rain or even all freezing rain is both models indicate a modest to strong southerly flow at 850 mb. This ultimately would warm and moisten the upper boundary layer to support a wintry mix or freezing rain over all snow. It is still too early to tell exactly what will happen but the threat is there for wintry precipitation.

The low pressure system is expected to move to the east and offshore Tuesday and Tuesday night. Some rain showers east of the mountains and some snow showers in the mountains could linger or remain from the low Tuesday afternoon and evening.

High pressure will build into the region Wednesday and Thursday. Drier and cold conditions will ensue. Expect below average temperatures each day.

AVIATION /14Z THURSDAY THROUGH MONDAY/. VFR through this evening for all terminals. Lowering cigs and encroaching RA/FZRA then become a concern late tonight and Friday. FZRA most likely CHO and MRB, with much less (but still some) risk IAD. Not particularly concerned at DCA/BWI/MTN for FZRA given later arrival of precip and warming easterly flow. Low cigs and vsby likely Friday night with rain. Improving to MVFR/VFR on Saturday as low lifts north and rain ends, though scattered showers may linger.

VFR conditions at all terminals Sunday and Sunday night. MVFR conditions possible at CHO and MRB on Monday with approaching light snow or a wintry mix. MVFR conditions possible at other terminals late Monday and Monday night. MVFR conditions could linger Tuesday with lingering rain or snow showers.

MARINE. SCA conditions continue in the central Bay, but that will end over the next couple of hours as high pressure builds to the north. The high pressure will slide east as low pressure moves up from the south tonight through Friday night, but not yet particularly concerned about SCA issues given stable air mass in place. SCA could become an issue as low pressure pulls away Saturday into Sunday.

Small craft advisory conditions possible Sunday as high pressure over the Great Lakes interacts with low pressure over New England. No marine hazards Sunday night through Monday night.

LWX WATCHES/WARNINGS/ADVISORIES. DC . None. MD . None. VA . None. WV . None. MARINE . Small Craft Advisory until noon EST today for ANZ534-543.

SYNOPSIS . RCM NEAR TERM . RCM/CJL SHORT TERM . RCM LONG TERM . KLW AVIATION . RCM/KLW/CJL MARINE . RCM/KLW/CJL


Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
WASD2 - 8594900 - Washington, DC 66 mi53 min SSW 2.9 G 5.1 39°F 43°F1039.2 hPa
BLTM2 - 8574680 - Baltimore, MD 69 mi65 min S 5.1 G 6 35°F 47°F1039.1 hPa
FSKM2 - 8574728 - Francis Scott Key Bridge, MD 73 mi53 min ESE 8 G 8.9 33°F 1039.5 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 mi48 minS 510.00 miFair36°F15°F42%1038.7 hPa
Eastern WV Regional Airport/Shepherd Field, WV18 mi48 minSE 510.00 miFair36°F18°F48%1037.9 hPa

Link to 5 minute data for KHGR

Wind History from HGR (wind in knots)
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NW10NW9NW8W7W10N4N6N5NE4N4N6CalmCalmCalmCalmCalm35S5
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2 days agoS8S6S10S13S9SE9S8S9S5S5S8S8S6S6S7S8S5SW3CalmSE6S5S4S34

Tide / Current Tables for Chain Bridge, D.C.
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Chain Bridge
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Thu -- 12:14 AM EST     Full Moon
Thu -- 03:00 AM EST     -0.10 feet Low Tide
Thu -- 07:17 AM EST     Sunrise
Thu -- 07:34 AM EST     Moonset
Thu -- 08:26 AM EST     2.53 feet High Tide
Thu -- 02:44 PM EST     -0.09 feet Low Tide
Thu -- 04:46 PM EST     Sunset
Thu -- 05:22 PM EST     Moonrise
Thu -- 08:28 PM EST     3.04 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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0.90.40.1-0.10.10.81.62.22.52.52.11.40.80.3-0-0.10.20.91.82.6332.62

Tide / Current Tables for Chain Bridge, Washington, D.C.
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Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.


Weather Map
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wmap_A
GEOS Local Image of Mid-Atlantic    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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Other links: Northern Pacific     Contential US     Full GOES-East
Wind Forecast for Baltimore, MD/Washington (14,3,4,5)
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Ground Weather Radar Station Sterling, VA
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