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803
FXUS65 KSLC 282107
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
307 PM MDT Wed Sep 28 2016

.SYNOPSIS...High pressure stretching north into the northern
Rockies region will weaken today, aided by northeastward
translation of shearing wave currently over SoCal. Moisture
associated with this feature will spread into far southern Utah
this morning, then will reach northern Utah by later this evening
This moisture will in large remain in place through late week. A
stronger trough will impact the region this weekend into early
next week.

&&

.SHORT TERM (THROUGH 06Z SATURDAY)...
Water Vapor loop shows ridging over the Rockies, while a closed
low was spinning over southern California. MDCARS winds
observations show a 90KT-130KT southwesterly jet across western
Canada. GOES/HRRR/12Z KSLC ROAB indicate precipitable water values
range from 0.15"-0.30" mountains to 0.60"-0.90" southern valleys.

As the closed low opens up tonight, convective chances begin to
increase across central and northern Utah. As this occurs, gusty
dry microburst winds due to some saturation across southern Utah
will likely emanate northward.

A trailing set of sheared waves will provide focus for renewed
convection tomorrow. With continued southerly tap, precipitable water
values, dewpoints and warm cloud layer thickness will increase
from today. Could see some locally heavy rainfall across the
southeastern portion of the forecast area.

By Friday the last of these waves should be passing on to the
northeast. Residual moisture will lead to afternoon
destabilization and isolated to scattered convection, mainly spine
of the mountains and eastern valleys.

.LONG TERM (AFTER 06Z SATURDAY)...
A deep trof is approaching the PacNW coast at the start of the
long term period with a southwest flow over UT. Some moisture is
forecast to be lingering over the nern CWA in the early morning
hours Sat with a potential for showers persisting over these same
areas.

A short wave ejecting out of the PacNW trof lifts into the nrn
Rockies on Sat pushing a weak boundary into nwrn UT and providing
enough upper support to set off scattered convection over mainly the
nrn and central CWA.

The main portion of the upstream trof then starts to move ashore
on Sun tightening the swly flow over the CWA and maintaining the
threat of mostly isolated convection over the nrn CWA persisting
into Sun night.

The latest med range guidance has trended towards a solution the
EC had several days ago when the first part of next week was out
at around 200 hours in the model run. This sends the main portion
of the upstream trof into a closed low over central NV by Mon
morning, slower and much deeper than prev runs. This low tracks
squarely thru nrn UT Mon thru Mon night bringing much cooler temps
and scattered to numerous showers to the nrn and central CWA.

This is a fairly large departure from prev runs, so have only
trended the forecast towards this solution as confidence is still
not high that this will be what actually occurs.

A drier northwest flow follows the closed low with some
discrepancy between models but overall expect a return towards
normal temps and the only threat of precip over the far nrn CWA.

&&

.AVIATION...
Winds at the SLC terminal are expected to switch to the southeast
around 02-04Z. Cloud cover and the chance of showers will increase
between 01Z and 09Z, with most likely impacts of gusty erratic
winds and ceilings below 7000 feet.

&&

.FIRE WEATHER...
Yesterday`s ERC values were below the 50th percentile across the
state.

Convection with little rainfall for the remainder of today across
southern Utah. Gusty microburst winds will likely emanate from
this this precipitation northward into central Utah this evening.

Scattered showers and storms will spread northward to include all
of Utah tomorrow and eastern Utah Friday. Profiles look to
moisten in the lower levels across southeast Utah, where wetting
rain chances are maximized.

Significant storm system develops along the west coast this
weekend, expecting to see an increase in southwest winds and
lowering RH values.

The storm system crosses Utah early next week, bringing a cooling
and moistening trend with a good shot of wetting rain/high
elevation snow across northern and portions of central Utah.

&&

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

$$

SHORT TERM/FIRE WEATHER...ROGOWSKI
LONG TERM...WILENSKY
AVIATION...SCHOENING

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http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php