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Friday, March 17, 2017

our infamous instability issues... (pm.17.mar.17)>

Friday's stats:

Low temp: 44.4F (6.9C)
High temp: 57.5F (14.2C)
Precipitation: 0.13" (3mm) -- updated @ 8:10pm

We had a rapid-fire round of thundershowers with hail that lasted all of 25 minutes, between 5:30 and just before 6:00pm -- otherwise this has been one of the better days of the last week and a half or so.  Full sunshine early this morning gave way to increasing mountain clouds not long after 10:00am, and that led the way to a lot of back-and-forth between sunshine and clouds throughout the remainder of the day, with the sound of rumbling thunder up-mountain from us during the afternoon.  And obviously, we finally got to get up-close and personal with the thunder for that brief period this evening.  My high temp in the upper part of town was the warmest I've recorded since I got back in town nine days ago.

Very often on this blog over the years we've discussed afternoon/evening instability issues here along the Dhauladhars.  Warmer air in the surface layers that builds up during the day has no choice but to rise as it heats up, encountering much cooler air parked over the mountains in the middle and upper-levels of the atmosphere.  That leads to convective cloud development, and eventually, shower/thunder development -- as long as that temperature disparity with increasing height is significant enough.  Even without much of a large-scale weather disturbance, we regularly see PM thundershowers erupt along the mountains under those circumstances, which drift our way if the upper-level winds are favorable.

There should be a marginal amount of instability again tomorrow (Sat) afternoon, and on Sunday as well, so we stand a chance of seeing another round or two of shower/thunder action during the afternoon or early evening hours.

The high pressure ridge which has been advertised the last few days is still on track to develop starting late Monday, and dominate the weather pattern for most of next week.  Temperatures should rise significantly, most likely erasing most of this lingering unseasonable winter chill we've been dealing with the last ten days or so.  There will also be cloud issues to deal with, but it's at least looking much more spring-like by Tuesday into Wednesday...