OI: Lake Sonoma Monday night

[Steve Gottlieb]

I’m planning on observing tomorrow night (Monday) at Lake Sonoma, unless there’s a downgrade in the forecast. Should be at the Lone Rock parking lot before 5:00.

Steve

[Peter Natscher]

Lake Sonoma: Windy and CSC forecasts fog/very high RH (>90%) by 9pm Tues.

[Peter Natscher]

Correction: I meant 9pm Monday night.

[matthew marcus]

I wish I could observe Monday, but I have work on Tuesday. I'm standing
down on tonight because the sky has crapped up and while the
Canmet-based forecasts (Astrospheric and CSC) look OK, the Heavens Above
and Clear Outside sites show increasing clouds. Bleah! I'm all dressed
up in my long underwear and thick socks with noplace to go.
mam

On 1/18/2026 3:05 PM, 'Peter Natscher' via The Astronomy Connection

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[Steve Gottlieb]

As you know, Peter, that depends on the model.  The National Weather Service forecast shows 2 mph wind (not exactly windy), about 80% RH, and a 5° difference between the temperature and dew point.  Furthermore, on Friday night, the CSC showed a high dew risk, and it was dry there.

Steve

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[Peter Natscher]

The forecasts from NWS for Lake Sonoma are recorded from the station at Hawkeye, elev. over 2,000 ft., twice the el of Lake Sonoma.  It recorded a very low RH last Friday 9pm which matched your experience 1,000 ft. lower.  Where, did you see a forecast for high RH (dew risk) on Friday night?

[Steve Gottlieb]

Peter, if the topic of weather at Lake Sonoma is of special interest to you, I can contact you off-list.

Steve

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[Ziad Khouri]

I'm aiming to be there around 5.

Ziad

[Mark Wagner]

Steve,

It is of interest to me, as I am always interested in particular models for prediction.  Looking at Lake Sonoma on the astronomy based predictors it does indeed look dismal from 6PM onward.  You use NWS instead (other tools too?).  I look forward to your posting the results.

I was laughing yesterday looking at tonight's forecasts.  All the usual places (except TB) seem to be dew magnets, *except* my backyard!

I'd actually like to see TAC used to help identify the most reliable tools.  If everyone posted where they went, maybe a screenshot of the prediction they used, and their assessment of the results, it could prove very useful.  Just making a habit of detailing what we experience.

Good luck tonight!

[matthew marcus]

Astrospheric now doesn't show the cloud map. What's with that? Does it
only work in Pro?

Did anyone go out yesterday (Sunday)? How was it?
mam

>> Weather Service forecast <https://forecast.weather.gov/
>> MapClick.php?
>> w0=t&w1=td&w2=wc&w3=sfcwind&w3u=1&w4=sky&w5=pop&w6=rh&w7=rain&w8=thunder&w9=snow&w10=fzg&w11=sleet&w13u=1&w14u=1&AheadHour=21&Submit=Submit&FcstType=graphical&textField1=38.7155&textField2=-123.0224&site=all&unit=0&dd=&bw=> shows 2 mph wind (not exactly windy), about 80% RH, and a 5° difference between the temperature and dew point.  Furthermore, on Friday night, the CSC showed a high dew risk, and it was dry there.

>>
>> Steve
>>
>>> On Jan 18, 2026, at 3:06 PM, 'Peter Natscher' via The
>>> Astronomy Connection (TAC) <sf-ba...@googlegroups.com> wrote:
>>>
>>> Correction: I meant 9pm Monday night.
>>>
>>> On Sunday, January 18, 2026 at 3:05:58 PM UTC-8 Peter
>>> Natscher wrote:
>>>
>>> Lake Sonoma: Windy and CSC forecasts fog/very high RH
>>> (>90%) by 9pm Tues.
>>>
>>> On Sunday, January 18, 2026 at 2:45:43 PM UTC-8 Steve
>>> Gottlieb wrote:
>>>
>>> I’m planning on observing tomorrow night (Monday) at
>>> Lake Sonoma, unless there’s a downgrade in the
>>> forecast. Should be at the Lone Rock parking lot
>>> before 5:00.
>>>
>>> Steve
>>>
>>>
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[Peter Natscher]

Maybe Lake Sonoma has a micro-climate that is difficult to forecast, like Fremont Peak does.   Generally, the forecast for Monday shows much high level cloudiness, stagnant air mass movement and high moisture levels.  Transparency will suffer and more than average sky brightness.