Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 251549

Area Forecast Discussion
National Weather Service Salt Lake City UT
849 AM MST Sat Feb 25 2017

.SYNOPSIS...A weak weather will cross the area this afternoon and
overnight. Yet another cold storm is on tap for the first part of
next week.


Water Vapor Satellite shows a positively tilted trough across the
Northern Rockies to a strong closed circulation off the Northern
California coast. 400-200mb MDCARS wind observations place a
125-155kt westerly jet from California across the Plains.
GOES/SLC 12Z RAOB/HRRR indicate that precipitable water values
vary from 0.05"-0.10" mountains to 0.15"-0.20" valleys.

This next storm system is cold yet lacking moisture. This is why
as the positively tilted trough crosses the region the models are
not producing a lot of precipitation. The cold pool aloft crosses
from north to south over the state during the weekend. It will be
cold enough that even a little snow could cause travel difficulties
especially tonight into Sunday across the central and southern
part of the state.

Additionally, early this morning a few showers have crossed in
the Northern Wasatch mountains from the Great Salt Lake.

The going forecast is in great shape, just a few tweaks including
utilizing the latest observations and model data for the hourly
temperature and RH curve. Rest unchanged.


A near zonal flow is in place over the forecast area this morning
as Utah remains in between two storm systems. Weak midlevel warm
advection will occur through midafternoon, but 700mb temperatures
will only warm around 1-2C for most areas. With SLC starting at
close to -16C this morning, the airmass will remain rather cold.

The upstream trough is becoming increasingly split and is currently
taking the form of an elongated trough extending from the southwest
Oregon coast through Saskatchewan. As a result, it will continue to
lose energy as the trough axis crosses Utah this afternoon and
overnight. In addition, moisture will be limited, so precipitation
is not expected to be significant for most areas. That being said,
expect few light snow showers mainly this afternoon and evening
across the north. Farther south, precipitation is expected to become
more focused across central and then southern Utah this evening and
overnight as low-level convergence increases there along a
tightening boundary.

A low-amplitude shortwave ridge is expected to build into the area
on Sunday as the trough exits the area. Warm advection will develop
once again, but the next storm system will quickly approach the area
so the airmass will not have a chance to warm significantly. This
next storm system will be a broader trough with a couple of embedded
shortwave disturbances, the first of which will cross the area
Sunday night into Monday and the second on Tuesday. This will keep a
cold and unsettled airmass in place with accumulating snow expected
down to many valleys.

The trough axis pushes east of the forecast area late Tuesday
into Wednesday morning, with clearing skies through the night.
Because of this clearing and the lingering cold airmass, Wednesday
morning will likely be the coldest morning of the week in many
locations. That said, some cloud cover could still persist into
Wednesday across the northern half of the CWA, as could some
isolated mountain snow showers.

With the ridge centered off the west coast through the day
Wednesday, a stable northwest flow develops over the area, with a
modest warming trend. This warming accelerates for Thursday and
Friday, as the ridge shifts more overhead, and temperatures will
likely exceed climatological normals by the end of the work week.

The challenge heading into the weekend will be tracking a cold
trough that pushes into the Pacific Northwest on Friday. At the
moment, this trough looks to largely remain north of Utah, though
the GFS does have shallow low level cold air push into the state on
Saturday, as the bulk of the trough moves through Montana. This
large feature will be worth keeping an eye on, though a plunge back
into the deep freeze looks unlikely for Utah at this time.


Winds at the SLC terminal will likely switch to the northwest
between 19Z and 22Z, though there is a slight chance that winds
simply remain southerly through the day. Ceilings are expected to
remain above 7000 feet through the day.





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