Clear skies and dry air are perfect conditions at night to radiate off all the heat of the day and that is precisely what is happening in the interior valleys of San Luis Obispo County.
Wednesday morning, these areas faced frost advisory conditions and Thursday morning looks even colder with sub-freezing temperatures between 30 and 32 degrees expected for 3 hours or more in the sheltered valleys.
Frost and freeze conditions will kill crops and other sensitive vegetation. Extended exposure to cold can cause hypothermia for animals and people, and vehicle windshields will be frosted.
After hard freeze and frost conditions are confirmed and more regular frost and freeze conditions happen, they are not always warned for, so it helps to pay attention to both sides of the forecast (the lows and the highs) through the winter months. A few more mornings will be in the frost freeze range, not just Thanksgiving morning.
Outside of the interior valleys, it will also be quite cool overnight in the coastal valleys with 40s and mid to upper 30s possible. There are no advisories yet for patchy frost but it looks like a narrow miss.
The magical thing about dry air and these high-pressure scenarios is that despite the cold starts, some warmer than average daytime highs are still likely with coastal valleys getting into the 70s and 80s for the next several days and even the coldest interior valleys will likely be 70-75.
Warm highs and cool lows will prevail all the way through next week thanks to a large and arching ridge over the West which will still promote more offshore flow.
To the south in SoCal, the offshore push is strong enough that Santa Ana winds are a concern for fire weather as the warm and dry and windy conditions mean that if a fire were to get going, dangerous fire weather behavior is possible.
Long-range models continue to want to break the ridge down in early December to "open the door" for low-pressure and cold fronts to shoot through the West. However, recent runs place the most significant rain chances too far north of us to change the drought picture.
