Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
310 PM MDT Wednesday Jul 1 2015
Synopsis...high pressure aloft centered across the western Great
Basin will shift east to The Four Corners this weekend. A gradual
drying trend can be expected through the end of the work week...then
increasing moisture and somewhat cooler temperatures will move into
the region for early next week.
Discussion...high pressure remains over the Great Basin this
afternoon...with the ridge axis over Nevada. A relatively moist
airmass remains over Utah and southwest Wyoming with precipitable waters around
1.0 inch. The repositioning of the ridge axis has put the area
under a more north/northwest flow...and this is allowing drier air to start
to nose in from the north. Still...with decent moisture in place
showers and thunderstorms have started developing over the higher
terrain...though coverage is a bit less than yesterday. Still
think development will continue into the early evening so have not
changed probability of precipitation much. Maxes also running a little bit cooler today
compared to yesterday but still 5-10f above seasonal norms.
Drier air will continue to make its way into the area Thursday and
Friday in northwesterly flow as the ridge axis moves slowly east.
Because of this...coverage of afternoon and evening showers and
thunderstorms will continue to decrease. By Saturday...the ridge
axis moves overhead so little change in moisture is expected...but
maxes should start to warm again with 100f possible again along
the Wasatch front.
Global models indicate ridge axis will be east of the forecast
area by Sunday...and the flow aloft will switch to S/SW. This will
draw tropical moisture back into the forecast area...increasing
chances for convection while bringing temperatures closer to
seasonal normals. Though guidance yesterday indicated this
moisture would be short lived...GFS/ec today are back to holding
onto this moisture through early next week. Current probability of precipitation cover the
trend well and did not make many changes in the extended period.
Aviation...VFR conditions will prevail at kslc through the taf
period with northwest winds switching back to the south around 04z.
Fire weather...the upper ridge centered near the Utah/Nevada border
this afternoon will slowly shift east the next several days...ending
up near The Four Corners region by early next week. Somewhat drier
air working south across the state tonight through Thursday will
serve to reduce the afternoon/evening convection. Enough residual
moisture will still exist for isolated terrain-based convection
The recentering of the upper ridge near The Four Corners will allow
moisture to return north into the region late Sunday/Monday. Showers
and thunderstorms will begin to increase in areal coverage Sunday
afternoon...then peak on Monday/Monday night.
Temperatures will remain above to well above early July normals
with relative humidity values low through the upcoming weekend. Increased
convective precipitation early next week will lead to cooler more
seasonal temperatures early in the week...with higher relative humidity values and
better night time recoveries.
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http://weather.Gov/saltlakecity (all lower case)
For frequently asked questions about the area forecast discussion
http://weather.Gov/saltlakecity/general/afd_faqs.Php (all lower case)