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 7:02AM||Sunset 4:36PM||Thursday December 5, 2019 1:24 PM MST (20:24 UTC)||Moonrise 2:24PM||Moonset 1:22AM||Illumination 64%|
7 Day Forecast for Marine Location Near Deer Trail, COHourly EDIT Help
Area Discussion for - Denver/Boulder, CO  (on/off)  Help NOTE: mouseover dotted underlined text for definition
FXUS65 KBOU 051750 AFDBOU
Area Forecast Discussion National Weather Service Denver/Boulder CO 1050 AM MST Thu Dec 5 2019
UPDATE. Issued at 1050 AM MST Thu Dec 5 2019
Temperatures have warmed to the upper 30s and lower 40s this morning with dew points now in the lower 30s along the I-25 corridor. This has raised wet bulb zero values well above freezing so that precipitation is now falling as rain on the plains. Mountain areas have received up to a few inches of snow, with the heaviest amounts from Grand County northward. Roads on the I-70 corridor have remained bare and wet according to web cameras.
The deformation band on the north side of the passing upper level low will continue producing precipitation over the forecast area through this afternoon. The rain on the plains may still change over to a mix of rain and snow later this afternoon after a few hours of evaporative cooling from precipitation processes. The latest models show precipitation hanging on for a few hours after 5 PM, so will make those changes in the forecast. For the most part the forecast is on track.
SHORT TERM. (Today and tonight) Issued at 328 AM MST Thu Dec 5 2019
Satellite shows a well defined circulation center over Central Utah, with bands of precipitation extending north and east of the center. The first of these has pushed into our forecast area, with snow in the northern mountains, and scattered rain/snow showers beginning to spread onto the nearby adjacent plains.
Shower coverage will expand through the morning with increasing QG lift ahead of the circulation center. That feature continues to be slower and farther north than early advertised. The latest data/timing shows this to reach Central Colorado by Noon, and then open up and slide east/southeast into southeast Colorado this afternoon. The northern mountains and portions of the plains are setting up to be under the upper level deformation zone, and therefore should see fairly widespread precipitation for a few hours later this morning through early afternoon. We've increased PoPs and QPF a little more to account for this.
The biggest challenge is still precipitation type across the I-25 Corridor and plains. Temperatures are starting off quite warm near the Front Range (close to 40F) but low levels are still dry, so surface wet bulb temperatures are hovering near or just below 32F. Therefore, initial precipitation could be rain/snow mix, or even light freezing rain toward Greeley where surface temperatures are initially much colder. Then, would expect saturation of the column with deeper precipitation, and likely more rain than snow from mid morning to early afternoon. By early to mid afternoon, we finally get into deeper cold air aloft with the trough passage. 700 mb temps drop to around -5C so more snow than rain later in the day. Whatever the case, we don't see much impact from the snow in the lower elevations as any accumulation would be light (mainly less than an inch) and confined to grassy/already snow covered areas. We can't rule out brief impacts in the deeper cold pool over Weld county where brief light freezing rain would be possible and road temperatures are running colder there.
In the mountains, snow will be fairly widespread through early afternoon with the deep synoptic lift but only weak orographic forcing. We may approach advisory criteria in the mountains of Jackson and Larimer Counties under/near the deformation zone. Most areas there should see 3-6 inches, but wouldn't be surprised to see a couple spots getting 8 or so through the evening. I-70 Mountain Corridor will be less with mostly 1 to 3 inch amounts expected with poor orographic and blocked moisture flow there on the front of this event.
Precipitation will decrease late this afternoon and evening, but have slowed this down based on the latest data. We'll probably see areas of fog develop on the plains tonight as T/Td spreads will be low and we expect clearing late.
LONG TERM. (Friday through Wednesday) Issued at 328 AM MST Thu Dec 5 2019
On Friday, a dry northwesterly flow aloft will be over the forecast area, with the upper level ridge axis over western CO. Surface high pressure will shift eastward with a lee side trough developing over eastern CO. By 12z Saturday, the ridge axis will be over eastern CO with the mid and upper level winds shifting southwesterly. Temperatures on Friday will be closer to normal with highs in the lower 40s, then warming to around 50 on Saturday. Late Saturday into Sunday, the flow will be more zonal with Pacific moisture increasing over western CO ahead of a 500 mb trough along the Pacific Northwest coast. This trough will move into the Northern Rockies by midday Sunday, then drop southeast into Wyoming/northern CO Sunday night through Monday. Snow will develop in the northern mountains late Saturday night/early Sunday and continue through Sunday night, ahead of the approaching trough axis. In the mid levels, 700 mb temperatures go from around -4C at 00z Sunday to -6C by 00z Monday. Overall, neutral to weak cold air advection but it is coupled with a good fetch of Pacific moisture over the mountains west of the Continental Divide. Higher west facing slopes could see 5-10 inches of snow in that time. The trough axis will move across northeast CO by midday Monday, with a strong northwesterly flow continuing into Tuesday. Best mid level cold air advection will be in the afternoon behind the trough axis, neutral by Tuesday morning, the weak mid level warm air advection by midday Tuesday. Snowfall late Monday into Tuesday will be primarily orographic, favoring northwest facing slopes. Maybe another shot of 3-7 inches of snow for the mountains at that time. Across the lower elevations, downslope will limit pops. Not much lower level support for more than slight chance snow showers late Sunday night and Monday. Timing of the cold front would appear to be in the 12-18z period on Monday. This will result in cooler temperatures for Monday and Tuesday, with high temperatures dropping into mid to upper 30s. By the middle of next week, a ridge of high pressure will be back over the state, with drier weather and temperatures closer to normal.
AVIATION. (For the 18Z TAFS through 18Z Friday afternoon) Issued at 1050 AM MST Thu Dec 5 2019
MVFR conditions should continue through the afternoon with rain through mid-afternoon. May see a mix of rain and snow late in the afternoon with precipitation coming to an end after 5 PM. Drying conditions and rising ceilings are expected overnight. Patchy fog may develop for a few hours overnight. No aviation impacts are expected Friday.
BOU WATCHES/WARNINGS/ADVISORIES. None.
UPDATE . Dankers SHORT TERM . DBB LONG TERM . Cooper AVIATION . Dankers
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|Denver Nexrad, CO||29 mi||90 min||SW 3||7.00 mi||Drizzle||39°F||37°F||93%||1015.9 hPa|
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Wind History from FTG (wind in knots)
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