Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 171548

Area Forecast Discussion
National Weather Service Salt Lake City UT
948 AM MDT Thu Aug 17 2017

.SYNOPSIS...A warming and drying trend will take place across the
area through Friday. Moisture will increase again from the south
over the weekend.


.DISCUSSION...Pretty quiet across the forecast area this morning
per visible satellite imagery, with some dissipating cloud cover
across the Book Cliffs and Castle Country of Eastern Utah. Water
vapor analysis shows the upper low sagging over southern Nevada
while subsident air moves into northwest Utah, further stretching
out a deformation zone across southern Utah. This will be the
favorable area for any afternoon convection to develop, although
any that does develop should be low in coverage. Precipitable
water values this morning across southern Utah are running 0.6 to
0.7 inches, while northern Utah is 0.5 to 0.6 inches. Kept PoPs
confined to the terrain, with a very slight increase, as this
will be the best lift mechanism to initiate development. Light
steering flow aloft points to low chances of any convection
drifting off the terrain. Overall, little changes made to the
morning forecast package. The warming and drying trend will remain
in place going into the weekend. Previous extended discussion

.PREVIOUS DISCUSSION (Issued 441 am MDT Thursday)...Finally
starting to see better agreement among the global models with
regard to the extended period. The ridge over the region is
expected to flatten during the day Saturday as a trough moves over
the top of it over Canada. This flow will keep the airmass on the
dry side, and should limit afternoon and evening convection to
the higher terrain.

On Sunday, the trough off the California coast is expected to close
off and strengthen, shifting the flow over the forecast area to a
more southerly direction. GFS has been consistent in indicating that
this flow will draw monsoonal moisture northward for the early to
middle part of the upcoming week. This combined with weak shortwaves
moving through the flow will increase coverage of convection.
Previous runs of the EC kept the forecast area mostly dry during
this period due to a different placement of the low, which caused
the flow to tap into a drier airmass. Though the latest EC is still
drier than the GFS, especially over western Utah, it is noticeably
more moist than previous runs, so have raised afternoon and evening
POPs Monday through day seven.

Temperatures look to remain fairly consistent through the extended
period with maxes running near to a few degrees above seasonal


.AVIATION...The SLC terminal will see VFR conditions throughout the
day. Southeast winds are expected to shift to the northwest between
18Z and 20Z.





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