OD Nats 2013 Aug 27, Weather Part II

Anyone remember the movie Groundhog Day? Today looks like a similar day compared to yesterday, except with more chance of convective precip in mix. Here's the discussion:

Area forecast discussion 
National Weather Service Salt Lake City Utah 
245 am MDT Tuesday Aug 27 2013 


Synopsis...the deep layer moisture plume with a tropical tap 
will remain in place through tonight. A more typical monsoonal 
pattern will then prevail tomorrow into the weekend. 


&& 


Discussion...water vapor loop shows the remnants of Ivo spilling 
northward into the region between a ridge over the central Continental U.S. And 
a trough off the Pacific coast. Acars 400-250mb wind observations 
place a 90-130kt southwesterly jet from central California into the 
northern rockies. Rap...GOES...GPS sensors...and 00z slc radiosonde observation 
indicate precipitable water values range from 0.80"-1.10" across the 
north to 1.40"-1.60" across the south and east. 


With the Flood Watch expiring a few hours ago at midnight and 
convection approaching from Arizona...already issued Flash Flood 
Watch for much of central and southern Utah through 11pm this 
evening. 


Dewpoints have rised to near 70f across far southern Utah and are in 
the middle 50s to middle 60s across most valleys. As the central Continental U.S. 
Ridge tries to build westward beginning today...moisture and 
weakening disturbances from Ivo will track further to the west. 
Drying and warming will gradually take place from east to 
west...though enough moisture will remain in place to support more 
traditional diurnal convection. 


Global models indicate a series of disturbances with origins over 
the Gulf of Mexico will round the broad central Continental U.S. Ridge and 
impact the Great Basin next weekend. Temperatures should cool as the 
western extent of the ridge is eroded by these disturbances and more 
expansive convection takes place. Not buying off on the drying 
offered by the GFS solution beyond next weekend. 

I think that sums it up. NWS bumped chance of TS from 30% to 40% for the SLC area and kept 30% for the Provo area. Up north we are looking at 30% chance around Ogden. What does all of this mean? Well, here's the relative humidity profile:



Again we're looking at a very deep layer of moisture that convective clouds can tap into. It's hard to imagine the day being usable for XC-- a day with half the TS possibility is hard to imagine!


Cloud base will likely be low again today, giving TS even more of a chance to blow up. Looking over the skewt plot validates what the forecast is anticipating, with a very deep layer of moisture aloft. On the bright side, winds below cloudbase will remain fairly light, at around 10 mph or less from the S...so I guess we got that going for us, which is nice.

And what about radar and water vapor imagery? Well,vapor loop shows an interesting space of drier air moving overhead at the moment, however, this is likely to give way to increased moisture within 2 hours from now (7am), and this period of less cloud will actually give more energy into the system with clearer skies for a bit, which will drive convective storms even stronger. Radar is quiet at the moment.




Bottom line: it's hard to imagine flying paragliders in this area today. I don't see a place drivable by 4 hours which could support an XC attempt with any certainty.

-CG