Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 260320
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
820 PM MST Sat Jan 25 2020

.SYNOPSIS...
High pressure aloft will settle over Utah through the weekend. A
fast moving storm system will impact the area Sunday night into
Monday morning. A second storm system will follow for late Tuesday
through Wednesday morning.

&&

.SHORT TERM (THROUGH 00Z WEDNESDAY)...
Fog continues to expand this evening with decreasing visibilities
across much of the Wasatch Front the West Dessert and in Castle
Country, despite some mid and high level cloud cover streaming
overhead. The trapped low-level moisture under a shallow inversion
layer, per the 00Z SLC sounding, will maintain this fog overnight.
With surface high pressure centered near southeast Wyoming, there
will be no opportunity to break the inversion given the light
winds and subsidence. Thus fog will continue overnight, with
bench locations especially likely to see worsening visibilities
after sunrise as some boundary layer mixing starts to develop and
lift the fog layer a bit. Otherwise, expect at least patchy fog to
linger into midday, with urban corridor haze becoming more
noticeable thereafter. Unfortunately there is little gradient
ahead of the next approaching storm system Sunday afternoon, and
thus it looks like winds wont really pick up until after the cold
front passage Sunday evening. Thus patchy fog and areas of haze
will likely be with us much of Sunday.

Mid/high clouds increase once again Sunday afternoon ahead of the
next trough which crosses overhead Monday morning. Dynamically
speaking, not too impressed with this system, given weak jet,
splitting nature and modest height falls and subsequent cold
advection. Given the splitting nature of this system, expect a
relative minimum between Ogden and Provo. North of Ogden, better
dynamics exist closer to the northern stream. Another area of
grater concern is across the central and southern mountains,
along with the I-15 corridor between Nephi and Cedar City. The
cold front is frontogenetic across central Nevada, though this
weakens greatly once entering Utah. However not fast enough to
reverse a period of strong omega through the dendritic snow growth
zone. And given this corridor`s response to northwest flow, there
could be some impacts. Had the lower snow levels well below
guidance to match the snow precipitation type along this portion
of the I-15 corridor seen on BUFKIT model forecast soundings. Was
not quite ready to pull the trigger on a Winter Weather Advisory,
but could see one being issued for this area in a future
forecast.

Building height/anticyclonic flow and warming aloft end the threat
of snow showers Monday. A weak trailing wave may keep a chance of snow
showers near the Idaho border Monday night.

The ridge that builds Monday night looks to weaken Tuesday in
advance of the next storm system, with precipitation developing
north to south across northern Utah Tuesday afternoon.

.LONG TERM (AFTER 00Z WEDNESDAY)...
The trough feature moving through late Tuesday from the Pacific
Northwest once again (broken record) looks to weaken as it advects
southeastward. This is due in part the parent trough splitting
and stretching as it becomes positively tilted with the far
northern branch up in Manitoba, Canada.

Another rather weak baroclinic zone structure will slide southeast
through Utah late Tuesday through Wednesday. Precip types at onset
for valleys may be some rain/snow mix but by Wednesday morning
should be all snow as the airmass cools. Just as quickly as it
approaches it will exit by late Wednesday night, thanks to a strong
120kt jet ushering the trough south and east. Another quick 1 to 3
inches for select valley areas might be possible (northern Utah) and
twice as much for the mountains.

Beyond this, ensembles have been pretty consistent in building in a
rather strong ridge from the west through next weekend. Some very
weak waves may bring light precip chances to the UT/ID border
Friday.


&&

.AVIATION...
LIFR conditions at the KSLC terminal in fog are expected to
continue through the night with expected improvement after 15z
Sunday. Light south winds may be variable at times. Improvement
during the day Sunday will be brief before the next front brings
precip to the terminal Sunday evening.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Dense Fog Advisory until 11 AM MST Sunday for UTZ002>005-008-012.

WY...None.
&&

$$

SHORT TERM...10/Church
LONG TERM...Dewey
AVIATION...Dewey

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

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


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