Cold Windy Pattern Setting Up For Sunday-Monday As Pattern Changes Force Arctic Air Into Pacific Northwest……Wind Advisories Hoisted For Mono County……Over Running Precip Begins Thursday Into Friday Over Milder Air….
Saturday January 14, 2012
Posted at 10:30 am by Howard
Quick Monday Am Update:
First…here is a link on a simple understanding of the NAO and AO supplied by another WX Dweeb….Doug Rowe
Thanks Doug for your input….
Just a few added points:
1. The 0C isotherm at 700mb (10,000ft) rises up from the south to Mammoth by Wednesday afternoon. So warm advection precipitation may begin as snow in Mammoth as early as Wednesday Am. However, with the 0C reaching Mammoth that afternoon…..cooler air in place will eventually mix out with the warmer air aloft…forcing the snow level to rise above 7000 feet.
2. We may actually may experience snow level that rise and fall Wednesday through Friday between 7000 feet and 9500 feet.
3. Although the 0C line moves well north of Mammoth Friday….there are times when micro-physical processes at work that can fool the weatherman with lower snow levels when the air is saturated through the Dendritic growth zone -12 to -18c at 20,000 feet when the 0c line can actually verify lower on the OAK sounding.
4. First EST QPF 5 to 6 inches Liquid EQ. 10,000ft and above (3 to 5 feet accumulation) by Tuesday morning the 24th
Quick Sunday Am Update:
1. Modified Arctic has invaded Washington State
2. Dry Cold Front moving through Northern Ca today stalling out about Tahoe…then moving again south to between MMH and Bishop by 4:00am (The front is Dry)
3. Windy today and cooler with highs about 40 at the village at MMH
4. Highs about 27 on MLK Day. Lows in the single digits Tuesday AM
5. As Upper High Anomaly develops over Eastern Siberia…Westerlies undercut block, that morphs into Rex formation by next weekend
6. Subtropical Ridge Builds over Eastern Pac mid-week effecting mid latitudes causing warming aloft into the Sierra.
7. Long Wet Fetch develops mid-week with rich subtropical plume expected to develop north of Hawaii within main wave later in the week.
8. Main Wave of rich PWAT to reach central west coast Friday then into Sierra during the afternoon. Snow levels will still be high; possibly still above 8500 to 9000 over Southern Mono County. Colder air expected to move into wave after 00z Sat. Based upon the new 12z Sunday GFS guidance….the 700MB 0C line doesn’t push south of Mammoth until after Midnight Friday NGT, so snow levels will probably stay pretty high or above 8000 Friday night until Midnight. More fine tuning later…..
Of Note: The GFS QPF from last night went hog wild with 5+through the next 7 days to as high as 10 inches of Liquid EQ through the 31st.
The ECMWF is much less. Lots will change over the next 5 days….however, confidence is high now that at least one to two significant precipitation events will effect the Mono County area over the next 10 days.
From Saturdays discussion:
A shift to Colder Windy weather is expected for the Eastern Sierra Sunday into early Monday as this mornings upper ridge builds into the Bering Sea (-WPO) with the return flow tapping cold Arctic air north of AK which then moves south off the AK coast then down off the BC into Washington State and Oregon. The upper ridge over Ca is being flattened today and by Sunday, its remains will be south of the Mex Border Sunday. The Surface front will bottom out about Tahoe Sunday Am then shift east. Cooling will come from lowering 700-500MB heights
As the cold storm pushes through, the upper flow will become Northwesterly. This is both a cooler and windier pattern for the Central Sierra, especially late Sunday into Monday Morning……However, it is still a dry pattern.
What the Dweebs see is the upper closed High Monday in the Bering Sea Retrograding into Eastern Siberia, while a good portion of the Westerlies break underneath. A very long and may I add wet fetch sets up by Tuesday. The source of the moisture is from the tropics west of Hawaii. Today’s 12Z GFS has PWAT forecasted higher then 1.50-1.75 inches within the fetch, Wednesday into Friday. The initial target is the Pacific Northwest…..then Northern Ca by Wednesday shifting south into Central Ca by Thursday/Friday.
Here is the problem…… What happens is that as the upper Anti cyclone shifts westward well west of the Dateline 160E, there is a tendency because of the teleconnection, for 500mb heights to rise about 140W with a flat subtropical ridge that extends north, then east to the Central Ca coast. 700mb temps over Mammoth increase to 0c by Thursday and with 1000-500mb thicknesses about 558DM, snow levels will likely be north of 8000ft and possiby 9000ft. Once and “if” the air-mass gets really saturated, there could be little difference in the snow level from the freezing level. So the Dweebs expect the possibility of some very heavy wet snow at and above 9000 to 10,000ft….Especially Friday in the over running pattern. Now the EC model looks a bit cooler so still time to adjust. By Friday night, the GFS has the Freezing level coming down rapidly. However, most of the fetch has shifted south with much drier air coming in from the north. This moist wet pattern is not the system that we are really waiting for. That is still looking like 10 days away or sooner of the ECMWF is correct. Better Vis later in the upcoming week……
All this Talk about the AO and SSW.
Yes there has been a Strato Warming event and yes the AO index is becoming more neutral and yes Arctic air is shifting further south out of the northern most Latts. However, the Forecast by pundits has been a real significant Plunge in the AO index to negative. The Dweebs do not see this in the GFS operational or Ensembles, What many now see is more of a neutral AO with some incursions to slightly negative…then returning to positive. I also see that all the hype of the big cold coming into the east as mostly hype. Patterns often repeat themselves during the Winter. So more and more of the Dweebs are shifting their opinions to the idea that the current cooling across the country will be short lived then confined to the northern tier states. That anomalous warmth will be returning to much of the CONUS soon. The climate models suggest cooler weather after the 4th of February over the western half of the CONUS.
The Dr Howard and the Dweebs…………………..:-)
Reference Glossary of Weather Terms
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.