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fxus65 kslc 192349 

Area forecast discussion
National Weather Service Salt Lake City Utah
449 PM MST sun Feb 19 2017 elongated upper level trough will continue to
exit the eastern Great Basin tonight. High pressure aloft will
develop over Utah Monday, with a mild southwest flow aloft Tuesday.
A potentially strong winter storm could impact the region beginning


Short term (through 00z friday) elongated upper trough with an
axis extending from the Pacific northwest states through The Four
Corners region and into western New Mexico continues to slowly shift
east this evening. Utah is already mostly behind the trough axis,
but is still seeing a few instability showers. These showers should
diminish after sunset with partial clearing of skies through this
evening. Overnight mins should generally run a few degrees cooler
tonight as a result.

A ridge will build into the area later tonight and clouds will
quickly increase again as 700mb warm advection develops.
Precipitation is expected to fill in again across the north, with
light precipitation expected with snow levels near 5500-6000ft. A
moist southwesterly flow will continue into tomorrow allowing
precipitation to continue at times through tomorrow night. The
northern Wasatch mountains and adjacent valleys will be favored in
this flow regime, but rising snow levels will Keep Mountain
accumulations limited. However, a tightening mslp gradient and 700mb
winds 45-55kt developing ahead of a deepening upstream system will
bring breezy to windy conditions to the western valleys and a
potential for strong gusts along exposed ridgelines late tomorrow
into Tuesday. A fairly well-mixed airmass on Tuesday is expected to
bring a return of much warmer temperatures.

The storm will eject through the West Coast and end up grazing
northern Utah Tuesday afternoon. However, this will push a cold
front into northern Utah late Tuesday afternoon through Tuesday
night with enough cold air to potentially bring snow to the valley
floors. With the responsible trough exiting the region Wednesday
morning and another trough deepening over the West Coast,
convergence into the baroclinic zone stalled over central Utah is
expected to strengthen. This will focus precipitation from around
west-central through northeast Utah before the front finally pushes
through the state Thursday. A cold, moist and somewhat unstable
northwesterly flow will then follow for Thursday.

This pattern will bring a return of more winter-like conditions to
the area with a potential for accumulating snow to the valley
floors. Some uncertainty still exists with regard to the
positioning of the baroclinic zone and temperatures relative to the
boundary, which would affect timing and location of heaviest snow.
For now, have kept snow amounts relatively light in the valleys but
some mountains, particularly the southern Wasatch and uintas could
end up seeing significant snow amounts.

Long term (after 00z friday)...once the trough slides to the east
Thursday evening, weak shortwave ridging is possible heading into
Friday. Any ridging will be very low amplitude, so warming will not
be significant; right now, models indicate 700mb temps near the
Utah/Idaho border increasing from -16c to -13c. Enough moisture lingers
that some light precip may be possible in this weak warm advection,
particularly across far northern Utah.

The next shortwave trough looks to slide across the Great Basin late
Friday through Saturday. Details with this trough begin to differ
significantly in the global models, but there is currently agreement
that the best forcing remains south and west of the forecast area,
eventually sliding through Arizona on Sunday. For now, have
maintained some low level pops through next weekend, especially in
the southern half of the County Warning Area.

With weak synoptic-scale forcing through most of the extended, the
biggest takeaway for the end of the week through the weekend is
probably that the airmass does not warm up significantly. This means
that temperatures should remain below seasonal normals through this
time, which may be a minor shock after the warm February we've been
having so far.


Aviation...there is a 30 percent chance of rain showers at the slc
terminal through 04z, with ceilings below 7000 feet possible under
these showers. Surface winds will likely remain from the south
through most of the taf period, though there is still a 20 percent
chance of winds switching to the northwest at times through 01z.


Slc watches/warnings/advisories...



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