Marine Weather and Tides
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 7:09AM||Sunset 4:37PM||Thursday December 12, 2019 6:05 AM MST (13:05 UTC)||Moonrise 6:15PM||Moonset 8:32AM||Illumination 99%|
7 Day Forecast for Marine Location Near Cherry Creek, COHourly EDIT Help
Area Discussion for - Denver/Boulder, CO  (on/off)  Help NOTE: mouseover dotted underlined text for definition
FXUS65 KBOU 121146 AFDBOU
Area Forecast Discussion National Weather Service Denver/Boulder CO 446 AM MST Thu Dec 12 2019
SHORT TERM. (Today and tonight) Issued at 405 AM MST Thu Dec 12 2019
The problem of the day this time around is the developing winter storm that is expected to move into the mountains by tonight which will then continue for several periods. Ahead of that, today should be a mild day as downsloping westerly flow continues. Moisture aloft will be increasing through the day, leading to mountain wave clouds over the plains and generally increasing clouds in the mountains. Snowfall is expected to begin in the mountains during the afternoon, but accumulation rates are not expected to increase until later tonight. When the storm arrives, abundant Pacific moisture is going to be moving over the state, being driven by a 130+ knot jet stream aloft. Strong orographic effects should produce light to moderate snowfall over west-facing exposures through tonight and Friday morning. Gusty winds are also expected due to the fast flow at mid and upper levels. Blowing and drifting snow could be a problem over the higher elevations through the duration of the storm. Will be upgrading the Winter Storm Watch to a Winter Storm Warning for tonight and Friday. The rest of the Winter Storm Watch will be left as is because of the uncertainty over how long the storm may continue. (See below) Snow accumulations with the initial surge of moisture are expected to be 12 to 18 inches by Friday afternoon. Continuing strong downslope effects in the lee of the mountains will keep the plains dry.
LONG TERM. (Friday through Wednesday) Issued at 430 AM MST Thu Dec 12 2019
Water vapor imagery shows a strong jet stream moving ashore over Oregon this morning with a plume of moisture that extends as far west as Hawaii's longitude. This jet and associated moisture plume will be responsible for the prolonged snow event across Colorado's mountains that lasts through this weekend. Global models predict this jet will enter Colorado Friday morning with maximum 300-200 mb winds of up to 180 knots. During this time, our CWA's mountains will be under the left exit region of the jet which will provide lift along with a quick moving shortwave trough. This will enhance snowfall rates to between one to two inches per hour Friday morning and create hazardous travel conditions. By Friday afternoon, the jet will move directly overhead with slight ridging building in behind the departing shortwave trough. This will decrease snowfall rates to around a half inch an hour. It is important to note that while snow rates will decrease Friday afternoon, the strong winds, gusting up to 60 mph at times, will create blowing snow and poor travel conditions. It is for this reason that the Winter Storm Warning goes through Friday evening with a Winter Storm Watch continuing immediately after the warning ends.
A secondary plume of moisture will arrive ahead of a shortwave trough Friday night. Snowfall rates will increase to one to two inches in the mountains with hazardous travel conditions. These snowfall rates will continue through the day Saturday and into Saturday evening before tapering off. The jet stream moves farther south to southern Colorado Saturday night which leads to the lull in snowfall. Models still show considerable differences for Sunday across our CWA but it appears a trough will deepen over the Four Corners region during the day. As this system moves eastward-northeastward, it will produce a swath of moderate snowfall. This swath will likely be farther south than the previous two systems and will hit the central and southern mountains harder than the northern mountains. By the time the snow ends Sunday night, we expect significant snowfall amounts especially on west facing mountain slopes. There was extensive discussion on the timing of warnings and watches for this storm as it will come in three waves. We determined that highlighting the first wave would be ideal at this time while signaling there is some uncertainty with the second and third waves. From Monday through Wednesday, a ridge will build over the western US keeping Colorado dry.
As for the plains and urban corridor, the westerly, downslope flow will keep conditions dry on Friday and Friday night. Strong gusts will be the biggest issue as they could reach up to 45 mph during the day. We may even see some loosely attached Christmas decorations taken for a ride if a gust gets a hold of them.
The second system will have better QG ascent aloft over the urban corridor and plains which will lead to a chance of snow. The ECMWF is the most bullish about snow amounts in the Denver area while other models keep the snow farther north along the Cheyenne Ridge. Since systems tend to come in slightly farther south and deeper than models predict, I trended the forecast toward the ECMWF and increased PoPs over much of the urban corridor and plains on Saturday.
The third system will have the best QG and frontogenesis aloft out of the three. This system appears it will hit southeastern Colorado the hardest but areas from Denver southward may still see light to moderate snow amounts. Confidence in the track and intensity of this system is still rather low but it will need to be watched closely for those traveling on Sunday. Monday through Wednesday will see dry conditions with moderating temperatures.
AVIATION. (For the 12Z TAFS through 12Z Friday morning) Issued at 405 AM MST Thu Dec 12 2019
Westerly winds at times will be about the only aviation impact through the next 24 hours, and most of the winds should be west of the I-25 corridor. Gusts up to 30 knots will be possible at times at KBJC. Winds at KDEN should be out of the southwest to west at speeds less than 15 knots. Mid and upper clouds will be increasing through today and tonight, but ceilings should remain above 6000 feet AGL. Mountains to the west will become obscured in clouds and snowfall. from this afternoon through tonight.
BOU WATCHES/WARNINGS/ADVISORIES. Winter Storm Warning from 5 PM this afternoon to 5 PM MST Friday for COZ031-033-034.
Winter Storm Watch from Friday afternoon through late Saturday night for COZ031-033-034.
SHORT TERM . Dankers LONG TERM . Danielson AVIATION . Dankers
Weather Reporting StationsEDIT (on/off)  Help NOTE: Click on distance to see the station location on a map
Airport ReportsEDIT (on/off)  Help Click EDIT to display multiple airports. Follow links for more data.
|Denver - Centennial Airport, CO||6 mi||73 min||SSE 5||10.00 mi||Mostly Cloudy||34°F||18°F||52%||1015.9 hPa|
|Buckley Air Force Base Airport, CO||9 mi||68 min||S 7||10.00 mi||Mostly Cloudy||35°F||17°F||49%||1015.6 hPa|
|Denver, Denver International Airport, CO||18 mi||73 min||SSW 8||10.00 mi||Mostly Cloudy||29°F||21°F||75%||1016.4 hPa|
|Denver Nexrad, CO||20 mi||72 min||S 6||10.00 mi||Fair||32°F||23°F||71%||1015.6 hPa|
|Broomfield / Jeffco, CO||23 mi||76 min||SE 6||10.00 mi||Fair||41°F||17°F||39%||1015.2 hPa|
Link to 5 minute data for KAPA
Wind History from APA (wind in knots)
|1 day ago||SE||NE||NW||NW||NE||N||N||NW||N||NW||S||S||SE||S||SE||S||SE||S||SE||SE||SE||SE||S|
|2 days ago||SE||SE||SE||SE||E||E||E||E||E||SE||SE||SE||S||Calm||S||S||SE||S||S||S||SE||E||E||Calm|
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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 Denver/Boulder, CO (8,2,3,4)(on/off)  Help
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