Trough/Vort-Max to bring Showers/Thunderstorms This Afternoon & Friday

Trough/Vort-Max to bring Showers/Thunderstorms This Afternoon & Friday

APRIL 3, 2014

A weak offshore trough and slightly more noticeable vort-max will slowly through the night tonight, sending the bulk of energy south along the coast into central/southern California, however increased lift and low-level moisture under colder air aloft has lead to an increasingly unstable airmass across northern California this afternoon, including surface-based CAPE values in the 200 – 500 j/kg. Mid/upper-level winds are meager given the bulk of jet-level winds continue to stream across central and southern California, however winds in general do veer with height. Low-level winds including 10 – 25mph surface winds in the valley support some modest low-level shear, with speed shear weakening with height. Best shear (somewhat terrain enhanced) exists north of Sacramento along the coastal mountains west of the central/northern Sacramento valley extending into the western half of the central and northern valley, and this is where the best potential for organized thunderstorms exists. Further south, a bit of upslope flow/orographics have supported cumulus development over the western slope of the sierra, where additional afternoon thunderstorm development is possible, though probably not organized.

Visible satellite imagery indicating quite a bit of cumulus developing in the north valley and eastern coastal mountains, as well as along the motherload and western slope of the sierra. Offshore, you can see a band of clouds associated with a weak front/vort-max inducing the convection ahead of it.

In the coastal mountains and adjacent valley (north of Colusa), shear and instability coupled with cooling with height support thunderstorms capable of hail and gusty winds. Lack of stronger upper level support at the moment will likely limit tornado threat.

Quick map depicting regions with the best convective potential today.

Friday, leftover cold air aloft and front edge of a jet will support additional convective development over the mountains and perhaps valley in the San Joaquin valley. Ridge builds in by the weekend and remains dominant through at least the middle to end of next week with highs climbing into the low to mid-80s by early in the week.

I wasn’t planning on posting an update for this system, but given the increasing thunderstorm threat today and possibly Friday felt a quick post would at least be needed.