Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 151732

Area Forecast Discussion
National Weather Service Salt Lake City UT
1032 AM MST Wed Nov 15 2017

.SYNOPSIS...A mild southwest flow will increase over the area
today through Thursday. A cold storm system will cross the region
Thursday night and Friday.


.DISCUSSION...A deep cold trof remains centered off the BC coast
in the ern Gulf of Alaska this morning with a southwest flow
aloft downstream from this trof across the Great Basin. Tropical
moisture is streaming into the western states on this southwest
flow with considerable mid and high clouds across the CWA.

The ern Pac trof gradually shears and shifts inland over the next
48s hrs or so with the swly flow increasing across the CWA. Winds
could reach advisory levels in the southwest valleys Thu aftn.

The tropical moisture also increases thru the day Thu and into Thu
night with precip becoming increasingly possible in areas favored
in swly flow, including far southwest UT.

The airmass stays warm in this moist pre frontal environment with
snow levels up near 10000 ft Thu aftn into the eve. Snow levels
will start to lower from the north Thu night as the associated
cold front starts to work its way into the CWA. The new 12z GFS is
now very similar to the 00z EC on timing of the trof and cold
front, but the GFS is colder, and would lower snow levels to the
valley floors north of about SLC on Fri morning, while they would
barely be to the valley floors along the ID border in the EC. The
EC has been very consistent on how its been handling this trof and
the GFS has been trending towards it last several runs, so would
continue to lean towards the EC on snow level timing. We will see
the 12z EC run shortly.

Both models push the front into srn UT Fri aftn with a weakening
band of precip, and turn the precip showery over the north.
Showers look to end Fri eve with a cold airmass in place setting
up a very cold morning on Sat.

Updated earlier to increase sky cover today. No other changes


.AVIATION...Light and variable winds at the SLC terminal will
become predominately light northerly after about 20Z. There is a
20 percent chance winds will not shift to the northwest and will
increase out of the south this afternoon.





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