Orographics on Steroids was why Mammoth Mt Picked up so much snow….More then twice as much as expected…..Unsetteled weather to continue through Wednesday with Snow Showers today and again Wednesday…..
Tuesday October 23, 2012
Posted at 9:30 am by Howard
Many Forecasters forget early in the season, especially after a long warm Summer, a drier then normal winter, that Mammoth Mt and its immediate area have a very special relationship when 700MB winds blow from the WSW. This storm was a classic case in point of how special local topography (land features), and Orographics (Mountain Effects upon moist winds) can play in forecasting snowfall and QPF. The wettest model, the ECMWF last Sunday, forecasted an inch of precip,(water EQ) just to the west of Mammoth Mt and Mammoth Pass over a 72 to 96 hr period ending Thursday AM. HPC forecasted about .5 to .75 of an inch and several forecasters indicated that was considered wet for the storm who’s upper jet favored the Northern Sierra.
What was actually recorded was close to 2.00 inches up on Mammoth Pass (1.72 according to CRFC), (subject to verification), and at 9000′ (unverified by manual means) 1.8 inches at the Main Lodge. (18 inches of snowfall); .87 inches W/10 inches of snow on Hillside Dr. near the village. Areas east of Highway 395 had little precipitation to speak of.
Mammoth Pass did not get anywhere near the amounts that some west side, Northern Sierra remote stations recorded. It received about double the amount compared to areas like Yosemite Valley (.89). Bridgeport on the other hand received .15 of H20, indicating how shadowed areas to the east were.
Winds were still westerly this morning at 700mb (10,000ft) and RH at the same level was about 60% to 70% but will decrease to 50% by this afternoon….so snow showers will continue over the higher terrain this morning but will diminish this afternoon. The next and last wave comes in early Wednesday morning. The flow at 700mb begins westerly but quickly shifts more northwesterly during the mid to late morning as the long wave Trof shifts into the Great Basin at the same time. Thus we loose our orographics pretty quickly after Sunrise Wednesday. The best chance of snowfall with this system will be around Sunrise, as later in the morning the upper flow becomes more northwesterly.
The weekend outlook is for partly cloudy but fair weather under a northwest flow. In that the upper high (500mb), remains well to our west, and apparently does not come in anytime soon, it will remain breezy over the upper elevations with highs in Mammoth in the 50s…lows in the 20s.
Next Trof about All Hallows Eve
Although it is about 10 days away…The Euro is saying that it will bring about 6 to 7 inches over the crest by November 1st. Lets see how well it does from a distance! 🙂
Dr Howard and the Dweebs…………………………….:-)
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Disclaimer: I have been a hobbyist meteorologist for over 30 years here in the Mammoth area and I do this for my personal enjoyment. The National Weather Service saves lives every day . . . I do not. When making important planning decisions please use information provided by the National Weather Service as they are the most knowledgeable and accurate information source available today.