Tuesday, December7, 2021
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Marine Weather and Tides
Portola, CA

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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 7:06AMSunset 4:38PM Tuesday December 7, 2021 3:46 PM PST (23:46 UTC) Moonrise 10:53AMMoonset 8:27PM Illumination 14% Phase: Waxing Crescent; Moon at 4 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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7 Day Forecast for Marine Location Near Portola, CA
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location: 39.82, -120.47     debug


Area Discussion for - Reno, NV
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FXUS65 KREV 072223 AFDREV

Area Forecast Discussion National Weather Service Reno NV 223 PM PST Tue Dec 7 2021

. A series of winter storms will impact the region over the next 7 to 10 days .

SYNOPSIS.

A quick but potent storm will bring an increased chance for snow Wednesday evening through Thursday, with some impacts likely down to lower elevations. Sharply colder conditions continue into the weekend. Next week looks to be quite active with potentially significant winter weather conditions.

SHORT TERM (Through Thursday).

In the wake of yesterday's rain and high elevation snow, several layers of dreary cloud cover exist from southern Washoe southward. While this cloud cover will gradually dissolve through the afternoon hours, some model soundings suggest low stratus will redevelop over the Sierra as early as midnight as increasing boundary-layer winds overnight result in mixing underneath a dry/stable layer which exists above 700mb. This will mainly remain an aviation nuisance for higher elevation terminals. Without precipitation in the picture, look for overnight low temperatures to be a little cooler than they were today; 20s for colder Sierra valleys and 30s elsewhere across Northeast CA and Western NV .

The highly advertised "slider" system, which looks to gently remind us we are in the month of December, will arrive tomorrow evening and persist through much of the day on Thursday. The associated surface cold front and forcing for this system look to enter Northeast California by mid/late afternoon - gradually traversing its way south and southeastward through the overnight hours. The major change for this forecast cycle is to drop the Winter Storm Watch and hoist a Winter Weather Advisory for elevations above 5,000ft. Here are the highlights:

* Snow: The previous forecast philosophy remains the same as models and ensemble guidance continues to be in good, consistent agreement for most if not all of us to receive some snow with this system (80-100% chance of measurable snow). Most likely snow totals are up to around 1 inch for lower elevations like Reno/Carson City, 5-10 inches for the high Sierra (3 to 5 around Lake Tahoe), and varying amounts between 1 to 3 inches across other portions of NE CA and Western NV. The "bust" scenario, as is always possible with slider systems, would be a trace to 1 inch below 6,000 feet with 2 to 4 inches in the higher elevations. The wetter scenario will be more impactful to higher elevations' totals where we could see up to 7 inches around the Lake and a foot or more above 9,000 feet in Alpine/Mono counties.

These ranges are pointed out to highlight some of the variability in the highest population areas, 4,500 feet plus or minus 500 feet. For now, we are thinking the largest impacts will be above 5,000 feet but if a break in cloud cover tomorrow night allows the valleys to cool off a little more, or perhaps winds stay a little weaker and we decouple - a quicker from rain, to rain/snow, then to all snow may give us a surprise for our Thursday morning commute. It can't hurt to allow extra time regardless; even slick and/or slushy roads can cause travel headaches. Plan for chain controls over any high elevation roads, regardless.

* Bonus Snow: There remains favorable conditions for lake effect snow bands to form off of the larger lakes- courtesy of moist, rapid cold-air advection over the relatively warmer bodies of water. With a surface temperature of 49 degrees at Lake Tahoe, modified forecast soundings show appreciable lake induced instability. If the fetch can remain NW to SE, areas like Markleeville, South Lake Tahoe, and Nixon (off of Pyramid Lake) may see rather quick and high snowfall totals during the day Thursday. If the fetch lines up out of the west, this could limit the lake-effect to Minden/Carson City or prevent it from happening at all. Nevertheless, keep an eye for this scenario to set up Thursday morning into Thursday late afternoon.

* Winds: Nothing blockbuster here . However, increasing southwesterly winds near ridge tops out ahead of the front will likely result in both aviation turbulence and gusty ridge tops. Peak wind gusts in the 20-30 mph will be common in the lower valleys and western Nevada, with 30-50 mph gusts in the Tahoe basin and lower portions of the eastern Sierra. Ridge gusts may top 70 mph.

-Dustin

LONG TERM (Friday Onward).

* A quiet but cool period is expected Friday and Saturday with shortwave ridging aloft behind the departing Thursday storm. Airmass is cool but not notably cold for this time of year, as noted in the lack of highlights in the ECMWF EFI for Min/MaxT. Even so, any areas that see snowfall Thursday could easily end up toward the lower end of NBM guidance ranges, with some teens or single digits for lows Friday and Saturday mornings.

* By now everyone's attention is focused on the Sunday-Wednesday period next week where a series of winter storms could affect the region. Large scale deep, cold, and slow moving trough off the coast in the ensemble means support this, however there remain some rather large ranges in the NBM guidance for snowfall even in the mountains. This is due to variances in individual storm tracks and even rain-snow lines. Example: Tioga Pass 75th percentile is 3 feet while 25th percentile is just 3 inches. For W Nevada one concern is over southerly flow bringing in just enough warm air, leading to a battle of rain versus snow for valley floors.

* At this point there are enough ECMWF and GEFS ensemble simulations showing significant amounts of snow in the Sierra and even into W Nevada to plan for possible prolonged travel disruptions. Keep an eye on the forecast - at this juncture confidence is high that we'll see storm(s) of some flavor but just how significant is still TBD.

-Chris

AVIATION.

VFR conditions will gradually return to most terminals as low stratus breaks and lifts across Sierra terminals. However, mountain obscurations will likely persist through the evening hours. MVFR, or potentially IFR ceilings will return to TRK by tomorrow morning with a lower end chance at TVL.

Wind gusts between 15 to 25 mph at terminals with ridge top gusts approaching 70 mph will yield the likelihood of aviation turbulence by late Wednesday morning. A cold front will push through the region from north to south tomorrow afternoon through the overnight hours. Snow at higher elevations and a rain/snow mix at lower elevation terminals will transition over to snow during the late night or early morning hours on Thursday. Flight restrictions are highly likely due to lower CIGS/VSBY.

Chance of seeing accumulating snow (0.1 inches) at RNO = 75% Chance of seeing accumulating snow (0.1 inches) at CXP/MEV = 80% Chance of seeing 1 inch of accumulating snow at TRK/TVL is 90% Chance of seeing 2 inches of accumulating snow at MMH = 60%

-Dustin

REV Watches/Warnings/Advisories. NV . Winter Weather Advisory from 4 PM Wednesday to 4 PM PST Thursday above 5000 feet in NVZ001>005.

CA . Winter Weather Advisory from 4 PM Wednesday to 4 PM PST Thursday above 5000 feet in CAZ070>073.



For more information from the National Weather Service visit . http://weather.gov/reno


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Reno/Stead, NV33 mi51 minSE 910.00 miMostly Cloudy48°F36°F62%1018.3 hPa

Link to 5 minute data for KRTS

Wind History from RTS (wind in knots)
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This daySW8W4NW3SW4NE30S3N5NE3000000000E6E5SE3E8SE8SE6
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2 days agoN80N5NW6N5N40000000W4N3000W3N10SW6N13N11N10

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