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Area forecast discussion 
National Weather Service Salt Lake City Utah
434 am MST Friday Jan 30 2015

Synopsis...a developing upper low over the southern Great Basin
will spread moisture into Utah through Saturday. The deepest
moisture will remain primarily over central and southern Utah.

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Short term (through 12z tuesday)...an upper trough situated along
the Pacific coast will gradually spread inland today before slowly
sagging southeast into northern mx Saturday. This trough is
anchored around an upper low spinning along the Southern California
coastline. A deep moisture tap originating from the inter-tropical convergence zone remains
intact early this morning...helping to transport abundant moisture
northward into the Desert Southwest. Some of this moisture has
spread across southern and central Utah overnight resulting in areas
of light rain and high elevation snowfall.

As moisture continues to increase across southern and central Utah
today anticipate precipitation to increase in coverage through the
daytime hours owing to isentropic upglide/low level Theta-E
advection. The northern extent of this moisture plume has reached
northern Utah early this morning...however given very weak forcing
any precipitation which falls through today will remain very light
and likely not measure.

As the upper trough works inland a middle level deformation axis
will spread across northern Utah overnight...helping to maintain
going precipitation across central and southern Utah. The Wasatch
front remains on the northern fringe of the precipitation shield
associated with this trough...and the best chance for
precipitation will come overnight with the passage of this
deformation axis.

700mb temperatures generally remain near -4c through much of the
event...and as such snow levels will likely remain in the
6500-7000 foot range with some fluctuations. Going Winter Weather
Advisory looks in reasonable shape and have left largely
unchanged.

Middle level ridging in the wake of this trough will quickly build
across the Great Basin Saturday bringing an end to precipitation
from north to south. This ridge will hold through Sunday...before
flattening as a moist onshore flow develops across the Pacific
northwest. The southern extent of this moisture will spread across
far northern Utah Monday into Tuesday bringing a chance for mountain
snowfall mainly north of I-80.



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Long term (after 12z tuesday)...the moist west-northwest flow
continues into Tuesday...with periods of precipitation possible in
the far north...especially in the higher terrain. Have kept probability of precipitation
generally in the 20-30 range for Tuesday and Wednesday...but these
will likely have to be raised once models lock into the
details/timing a little better. Have also increased winds across
southwest Wyoming and in utahs northern mountains through
midweek...with flow increasing considerably over the area...and
700mb winds prognosticated to reach as high as 45 knots near the Utah/Idaho
border.

This moist pattern with a flatter ridge lingers longer in the models
than it did last night...with cloud cover potentially persisting
across the north into Wednesday night or Thursday. The ridge is
still forecast to amplify considerably through the day
Thursday...with a quick warming trend and increasing southwest flow
over the County Warning Area. While inversions are still likely to set up in the
boundary layer...have kept a good warming trend in both the valleys
and mountains for Thursday and Friday...matching trends that have
been observed under warm high pressure the last couple of weeks.

Looking ahead to days 8-10...weak shortwaves may continue to brush
the County Warning Area while riding over top of the ridge...but no major storms
appear to be on the horizon...as a mean ridge continues to dominate
the weather pattern across the Great Basin and Desert Southwest.

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Aviation...ceilings at the slc terminal are expected to lower to near
6k feet above ground level by 05z as a weak disturbance moves across northern Utah.
There is a 40 percent chance that ceilings will remain above 7k feet above ground level
through 06-07z. Winds will likely remain light southerly through the
night.

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Slc watches/warnings/advisories...
Utah...Winter Weather Advisory until 4 PM MST Saturday for utz010-013-
517-518.

Wyoming...none.
&&

$$

Seaman/schoening

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