Monsoonal Action Possible Through Thursday

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Monsoonal moisture streaming northeast including precipitable water values in excess of an inch and surface dew points in the 50s in the lower elevations, combined with bands of lift and elevated instability rotating around a very strong ridge in the desert southwest will support daily thunderstorm development over the mountains, which should continue through at least Thursday.

Large ridge sitting over UT/NV spiraling around monsoonal moisture and associated convective activity.

Large ridge sitting over UT/NV spiraling around monsoonal moisture and associated convective activity.

During the day, storms should mainly be confined to the higher elevations due to there being an extreme thermal inversion over the Sacramento valley. Overnight, elevated instability and increased surface moisture recovery may support some nocturnal convective activity in the lower elevations (foothills and valley).

Valley thunderstorm chances will increase each day, peaking Wednesday night into Thursday as moisture and instability increases, before the ridge begins to weaken a bit and slide eastward.

Tuesday and Wednesday storms could become fairly widespread by late afternoon… potentially spreading into the valley in some places before sunset before chances increase further overnight as elevated instability increases above 850mb. As stated earlier, the best chance of thunderstorms for the lower elevations is expected Tuesday night and Wednesday night, each lingering into the next morning before diurnal convection develops in the mountains and nocturnal convection collapses.

Though shear will remain fairly weak, decent elevated instability and decent moisture will support elevated thunderstorms capable of hail and potentially strong or perhaps severe wind gusts given a slowly moistening sub-cloud layer. These types of thunderstorms (elevated) are known to produce some spectacular amounts of lightning as well… some of which could end up being dry due to the small overall convective precipitation cores. Inside the precipitation cores, on top of hail in the stronger storms, very heavy rainfall is possible given the decent monsoonal moisture surging into the area.

Simple graphic depicting the convective threat over the next few days.

Simple graphic depicting the convective threat over the next few days.

If chances change or become more likely, I’ll go ahead and post additional updates over the next couple of days. Check the comments of short term updates as well as the Facebook page.

Showing 2 comments
  • wxtracker15

    Looking like it’ll be a pretty active day today (Tuesday), with MUCAPEs in excess of 1,000j/kg over the higher elevations and dew points up to 50 degrees in the sierra. Wouldn’t doubt seeing multiple strong or perhaps severe storms with how everything is setting up.

  • wxtracker15

    Many flash flood warnings have been issued across the sierra this afternoon… all of which north of Tahoe, along with a couple of severe thunderstorm warnings earlier.
    Radar image: http://images.norcalweather.net/albums/radar/482.png

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