Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 220845

Area Forecast Discussion
National Weather Service Salt Lake City UT
245 AM MDT Sun Oct 22 2017

.SYNOPSIS...A mild westerly flow aloft will result in warmer
temperatures today. A weak weather disturbance will bring
slightly cooler temperatures to the region tomorrow. Strengthening
high pressure across the western states will bring warm and dry
conditions to the Great Basin midweek.


Water Vapor Satellite shows a low amplitude ridge from the
Southwest CONUS. 400-200mb MDCARS wind observations place a
125-155kt anticyclonic jet from the Pacific Northwest and the
Rockies. GOES/SLC 00Z RAOB/HRRR indicate that precipitable water
values vary from 0.25"-0.33" mountains and eastern valleys to
0.45"-0.60" western valleys.

Strong height rises currently occurring over the region. With the
jet so far to our north, and best warm advection already into
Wyoming, precipitation chances along the Idaho border continue to
diminish early this morning.

The next disturbance drops out of western Canada into the northern
Rockies later today and tonight. With the jet and height falls
well to the north no significant weather is expected for Utah. A
shallow cool front does cross the region from north to south
tonight. Northerly winds increase, with local air quality

Only a short respite in the warming trend aloft, which continues
once again Tuesday. However many inverted valleys will not
realize the full warming Tuesday. Air quality is expected to
diminish midweek with stagnant conditions settling in.

Like the last few days of model runs have indicated, a
developmental trough will approach the Pacific Northwest coast
Wednesday morning. At the same time, the upper level ridge will
flatten and retrograde west. This will allow the trough to
continue to dig into the West Thursday.

Timing of the associated frontal passage varies between the global
models and ensembles, but at this point much of the guidance points
to a fairly strong cold front crossing the state Thursday with the
potential for jet support/orographic upglide to enhance
precipitation near and behind the cold front. The 00Z GFS solution
continues the trend of the GFS indicating this trough to be more of
glancing blow to the state.  The 00Z EC solution remains deeper and
colder. The 00Z Canadian, however, features a stronger ridge and
thus a solution with the trough splitting closer to the Pacific
Coast and minoring out by the time it reaches Utah.

For now, continued the trend of keeping pops in the forecast across
portions of northern and central Utah Thursday with cooler
temperatures. Confidence in this portion of the forecast is much
lower than average given the large variation in model solutions.

In the wake of the Thursday trough, ridging rebounds across the
Interior West, though the area remains under north to northwesterly
flow, limiting any potential warming.


Southerly winds will continue at the SLC terminal through the
morning, shifting to the northwest between 19-21Z. Ceilings are
expected to remain at or above 7000 feet AGL.




SHORT TERM...Rogowski

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