SLOweather

All of us at SLOweather wish you a safe and merry holiday season. The weather looks like is could be a bit “frightful” with the NWS calling for “Rain, with thunderstorms also possible after 10am. Some of the storms could produce small hail. High near 56. Breezy, with a south southeast wind between 15 and 24 mph, with gusts as high as 33 mph. Chance of precipitation is 90%.”

This would seem to verify “Red sky at night, sailor’s delight. Red sky in morning, sailor’s warning”, as this was the sky to the southeast a little after 6 this morning…

And the wind has swung around to the southeast from the prevailing northwest.

Happy first day of winter! It arrived at 4:04 AM local time as the sun crossed the equator northbound. Today has the least amount of daylight for the year, and the days will begin to get longer again now.

It looks like a wet week and Christmas holiday are in store for us. Stay warm and dry…

Tonight’s full Cold  moon rose at 4:55 PM PST locally, and will set tomorrow morning at 8:20 AM.  It’s also known as the Full Oak Moon and Full Long Nights Moon.

PG&E’s John Lindsey’s latest Atmospheric Update has this interesting line…

“This cold front may result in significant accumulations of snow in the coastal mountains.”

—

ATMOSPHERIC CONDITION:

     A vigorous 990 mb low pressure system off Washington state
     will move slowly down the west coast over the next 96 hours. 

     The first associated cold front from this low pressure system
     will pass the San Luis Obispo area between 4 a.m. and 8 a.m on
     Saturday morning with increasing clouds and a few scattered
     sprinkles/light rain showers.

     The main effect of this cold front will be strong to gale force
     northwesterly winds and much cooler temperatures on Saturday after
     the frontal passage. Snow levels will lower to about 2,500 feet
     by Saturday afternoon. A slight chance of a sprinkles/light
     rain showers will continue through Saturday night.

     The winds will decrease and shift out of the southwest on Sunday
     as yet another cold front passes our area late Sunday with rain and

     snow above 2,500 feet.  Rainfall will be mostly light to moderate
     late Sunday afternoon through Monday morning. Rain fall amounts
with
     this system are expected to range between 0.75 and 1.25 inches.

     This cold front may result in significant accumulations of snow in
     the coastal mountains. Rain Showers are expected to continue
through
     Wednesday morning as this very cold low pressure system moves over
     the San Luis Obispo area. 

     Another storm system is expected to produce rain and increasing
     southerly winds next Friday and Saturday.

Halo around the moon, Thursday evening about 11 PM…

Last night there was a halo around the moon about 9PM. This usually portends rain in the next few days. Sure enough, both the NWS and our own WxSim are forecasting various chances of rain starting Friday evening through next Wednesday.

From http://home.hiwaay.net/~krcool/Astro/moon/moonring/:

The ring that appears around the moon arises from light passing through six-sided ice crystals high in the atmosphere. These ice crystals refract, or bend, light in the same manner that a camera lens bends light. The ring has a diameter of 22° , and sometimes, if you are lucky, it is also possible to detect a second ring, 44° diameter. Thin high cirrus clouds lofting at 20,000 feet or more contain tiny ice crystals that originate from the freezing of super cooled water droplets. These crystals behave like jewels refracting and reflecting in different directions.

The ice crystals that cover the halo signify high altitude, thin cirrus clouds that normally precede a warm front by one or two days. Typically, a warm front will be associated with a low pressure system which is commonly referred to as a storm.