Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 281237

Area Forecast Discussion
National Weather Service Salt Lake City UT
537 AM MST Tue Feb 28 2017

.SYNOPSIS...The next storm system will cross the area today. An
increasingly dry and warmer westerly flow aloft will set up for the
latter half of the week.


.SHORT TERM (THROUGH 12Z FRIDAY)...The 700mb baroclinic zone from
the last trough extends across south-central through southeast Utah
this morning. It is still producing a band of precipitation along it,
with some upper-level support owing to the right entrance region of
the upper jet which will be exiting Utah this morning. The
baroclinic zone and associated precipitation band will continue to
sag south and weaken, exiting the forecast area around midmorning.
The airmass supports snow levels down to near 5000ft. With
additional accumulations expected the next few hours across the
higher elevations of south-central Utah, have opted to extend the
Winter Weather Advisory for that zone through 8am. Otherwise, other
remaining highlights were allowed to expire.

Low-level moisture remains in place in many areas, especially banked
against the terrain and in some of the smaller enclosed valleys.
Light snow or fog has been associated with this moisture.

Otherwise, Utah remains under a cyclonic flow aloft as the next
shortwave trough approaches the area. The trough axis is expected to
cross Utah during the afternoon hours. Light snow is expected to
start filling in across northern Utah later this morning ahead of
this trough, with snow intensifying around midday through early
afternoon and spreading into central Utah. A cold, moist, and
unstable northwesterly flow will follow the trough axis for late
afternoon and into the overnight hours, keeping some snow showers in
place. Overall, snow totals are not expected to be very significant
due to the largely showery nature and short duration of the heaviest
snow. However, there is a wild card in the Great Salt Lake, as there
is a small chance it could produce some enhanced showers tonight and
bring locally higher accumulations to portions of Salt Lake and
Davis Counties.

The northwesterly flow aloft will continue through Thursday, but the
airmass will become drier and more stable as 700mb warm advection
commences. Would not expect this pattern to allow much if any
precipitation. However, temperatures will trend warmer to begin the
first day of meteorological spring and return to more seasonable
levels by Thursday.

.LONG TERM (After 12Z Friday)...A rather weak wave is progged to
graze northern Utah during the day Friday, weakening the ridge and
perhaps resulting in a few showers over the higher terrain by the
evening hours. Behind the wave, zonal flow is expected to prevail
for the first half of the weekend as the warming trend continues.

EC/GFS both show a trough moving onshore along the Pacific coast on
Sunday, resulting in increasing southwest flow over the forecast
area. Moisture is expected to increase over northern Utah during the
day Sunday out ahead of the system, perhaps resulting in a bit of
precip. The system is then expected to move across the state Sunday
evening into Monday. 00Z runs all showed a grazing system bringing a
weak and mostly dry frontal boundary into northern Utah. However,
06Z GFS is back to a solution that tracks the system farther south
that would bring colder air and a better chance of precip for
northern Utah. For this forecast package, have favored the grazing
system. GFS keeps some lingering moisture and instability over Utah
and southwest Wyoming into day seven, while the EC is quicker to
move high pressure back in. Have opted to keep some POPs in for day
seven at this time.


.AVIATION...At the SLC terminal...VFR conditions are expected to
prevail during the early morning with occasional cigs around 6000
feet AGL. Conditions are expected to deteriorate to low-end MVFR or
high-end IFR around midday as snow moves back into the terminal
before improving by the early evening. Southeast winds are expected
to shift to the northwest between 18Z and 20Z.


UT...Winter Weather Advisory until 8 AM MST this morning for UTZ020.




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