Monday, October 16, 2017, 11:55 PM EDT
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Area Forecast Discussion
Valid At
Wed, Dec 31, 7:00pm EST
FXUS65 KSLC 170247
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
847 PM MDT Mon Oct 16 2017

.SYNOPSIS...A warming trend will continue through the middle portion 
of the week as high pressure remains in place. The next storm system 
is forecast to cross the area Friday into Saturday morning. 

&&

.DISCUSSION...
Water Vapor Satellite shows a ridge building in from the 
southwest. 400-200mb MDCARS wind observations place a 60-90kt 
anticyclonic jet from the Pacific Northwest into the Central
Rockies. GOES/SLC 00Z RAOB/HRRR indicate that precipitable water 
values vary from 0.05"-0.10" southern Utah and mountains to 
0.15"-0.25" northern valleys.

The ridge axis is expected to shift east from Nevada overnight,
with an increase of cirrus. Amount of cirrus should not diminish 
radiational cooling significantly, and with a very dry airmass in 
place temperatures should dip overnight. Lowered overnight lows 
especially in locations with inverted conditions. The temperature
trend however is warmer than last night as the 850-700mb thickness
continues to increase.

Going forecast in great shape. Updated diurnal T/RH curve based on
latest observations and guidance.

&&

.PREVIOUS DISCUSSION...
High pressure remains centered just to the west of the forecast 
area this afternoon, resulting in a dry and stable west to 
northwest flow. The airmass at 700mb is in the +6C to +8C range, 
resulting in continued mild conditions over the higher terrain. 
Though noticeably warmer than yesterday in the valleys, limited 
mixing is inhibiting these temperatures from being fully realized 
in the valleys. As a result, maxes are running just a few degrees 
below seasonal normals. 

The ridge is expected to track east tonight and tomorrow as it
flattens, with the axis moving east of the forecast area by
tomorrow afternoon. The resultant west to southwest flow will
allow for improved mixing, resulting in further warming in the
valleys and allowing those maxes to warm to values a little above
climo. 

Models have been consistent in indicating that a rather weak
shortwave will impact southern Utah late Tuesday into Wednesday,
though they continue to disagree with regard to the precise track
of this wave. The main impact of this wave will be to increase
cloud cover somewhat, with little if any associated precipitation
anticipated. Behind this wave, the flow aloft is expected to
become more southerly beginning Thursday ahead of the next
approaching storm system, allowing for more mixing and warming
valley temps just a bit. These winds could become breezy for many
locations across the forecast area on Friday as the system and
associated cold front approach. 

The late week trough continues to trend less amplified and more 
progressive in guidance, with the H5 cold pool remaining north of 
the UT/ID border with passage late Friday/Friday night. With this,
both any connection to deeper moisture from the south, or strong 
deep layer CAA from the north are lost. Guidance continues to 
portray a decent mid level baroclinic zone with passage of the 
cold front, but with upper level support just a bit too far north 
the frontal push should be fairly shallow, with any precip 
confined to this zone Friday evening through mid level axis 
passage early Sat morning. Model QPF has decreased as such (both 
in areal coverage and significance). Have continued a trend of 
lowering PoPs this package.

Warm advection in slightly anticyclonic w-nw flow will punch into 
northern portions of the area rapidly Saturday into the overnight 
hours. Outside of a net increase/maintenance of clouds over the 
north, do not foresee much precip threat in this pattern as the 
better forcing remains tied north closer to the jet. 

Thereafter through the end of the period mid level ridging is 
expected to build into the Great Basin region yielding another 
period of tranquil and near seasonal conditions early next week.

&&

.AVIATION...
Operational weather concerns will remain minimal at the KSLC 
terminal through the valid TAF period. Winds are calm, and 
southeast drainage flow is expected to develop during the next 
hour or two.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

PUBLIC...Rogowski/Traphagan/Merrill
AVIATION...Rogowski

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