Rain showers are expected through Saturday. Then a bigger storm arrives Sunday into Monday. High snow levels through Sunday night, then falling Monday. A quieter pattern by the middle of next week.
Short Term Forecast
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Okay, back to the forecast...
We have a lot to go through this morning with the precipitation streaming in today (Thursday) all the way through Tuesday. But the big story will be the bomb cyclone for Sunday into Monday.
We have a very strong storm by October standards in the northeast Pacific, and an even bigger one behind that which will hit us Sunday into Monday.
For today we have light showers streaming in off of the Pacific. Snow levels are high around 10,000 ft. this morning and rising to over 11,000 ft. by this afternoon. Expected scattered showers with highs in the 50s at lake level. Ridgetop winds from the southwest gusting up to 50+ mph.
A colder and wetter system moves through Friday. This system has been trending slightly farther south and wetter the last few days. Steady precipitation is expected to push in around daybreak Friday and clear out later in the afternoon. Here is a look at our forecast radar.
Snow levels start out above 9000 ft. Friday morning, but then fall to 8000 ft. by late morning and could bottom out around 7000 ft. by the time the precipitation ends. Most of the precipitation is done by then so snow accumulations should mostly be above 8000 ft.
The latest model runs show 0.5 - 1.0 inches of total precipitation west of the lake up along the Sierra crest, and decent spillover to the east side of the lake with 0.4 - 0.8 inches of precipitation.
Time to dust off the snowfall calculator. This will be a wet snow for the higher elevations with 1-6 inches the general idea above 8000 ft.
Ridgetop winds are expected to gust to over 100+ mph from the southwest during the day and then coming down Friday night.
We may see a break in the precipitation Friday night into Saturday morning. Then a weaker system moves through Saturday afternoon/evening.
Expecting just scattered showers with snow levels possibly not much lower than the freezing levels with the light precip. Snow levels may be between 7500-8500 ft. Not expecting more than a coating to an inch of snow for the higher elevations. Ridgetop winds gusting up to 60+ mph.
Sunday - Monday Storm:
This storm is not only looking impressive by October standards, but by winter standards. The latest model runs show low pressure quickly dropping as the low spins towards the West Coast, possibly bottoming out around 940mb. That is a weak/moderate hurricane pressure and storms that quickly deepen like this over the Pacific are given the name "bomb cyclones".
We do see storms with pressure as low as 920mb once in a while, but this is a strong storm. Here is a look at the storm moving in Sunday.
It will have strong winds and will be tapping into copious amounts of Pacific moisture. Check out the Atmospheric River (AR) making landfall into CA and taking aim at the Sierra Sunday.
Ridgetop winds will increase with gusts over 130 mph Sunday! Below is a look at the OpenSummit.com wind forecast for the top of Mt. Rose. Ridgetop gusts could continue to be 70+ mph through Monday.
The last time we had a storm this strong and wet was the AR event we saw last January that saved our season. This one will get the season going for the upper elevations. As usual with these types of storms, we will see fluctuating snow levels which makes any snowfall forecasts challenging.
The lift from the mountains increases the already heavy precipitation amounts. This system could see moderate/heavy precipitation rates Sunday morning through Monday afternoon, a 36-hour duration as the AR slowly shifts south through CA. Then the cold front and post-frontal showers continue snow into Monday night with snow showers possible into Tuesday morning as the main low-pressure center moves inland to our north.
The forecast models are in decent agreement for a storm this big, and converging on a solution. The spread among the models is only around 2 inches with total precipitation amounts this morning of 6-8 inches along the crest by Tuesday morning! Plenty of spillover to the east side of the lake and into Reno. Totals of 4-6 inches of total liquid!
Snowfall will be tricky to forecast. Snow levels may start around 7500 ft. early Sunday morning but then rise with the warmer Pacific air streaming in with the moisture flow. Snow levels may rise to around 9500-10,000 ft. by midday Sunday, then falling back down to around 8000-8500 ft. by Sunday evening. So not expecting much snow to accumulate below 9000 ft. on Sunday during the day.
Sunday night the snow levels could fall to around 7000-7500 ft. Sunday night as the AR shifts south and we get on the colder side with colder air beginning to work in. Then Monday morning snow levels may drop to around 5500-6000 ft. by mid-morning and stay there through the end of the storm Tuesday morning. Snow starts to accumulate above 7000 ft. Sunday night and then down to lake level by late morning Monday.
Based on the latest model runs for total precipitation and the timing of the snow levels falling, here is my initial guestimate for total snowfall by Tuesday morning.
The amounts could be higher below 8000 ft. if the snow levels fall faster, for the upper mountains a general 2-4+ feet expected. We still have a few more days to fine-tune the details. I'll be posting daily. Confidence is growing in a significant storm as the majority of the models are converging on a very wet solution and coming into good agreement.
By next Wednesday high pressure builds in over CA and we should see a drier 2nd half of the week.
We could see the trough dig back south into northern CA by the end of the month, possibly allowing a final system to bring some rain & snow around the 30th.
Then the long-range models continue to suggest that high pressure builds back in for the 1st week of November.
It could be a dirty ridge though with weaker systems making their way down into northern CA. Plenty of time to keep an eye on that. Plenty to get through over the next 5 days...
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