Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 272220

Area Forecast Discussion
National Weather Service Salt Lake City UT
420 PM MDT Tue Jun 27 2017

.SYNOPSIS...A westerly flow will remain over the forecast area
through Wednesday. A cold front will cross northern and central
Utah Wednesday night into Thursday before high pressure returns
beginning Friday.


.SHORT TERM (Through 12Z Friday)...The forecast area is under a
zonal flow this afternoon in between two troughs. The first
exited the forecast area this morning but is keeping enough
instability in place for some cumulus clouds over the higher
terrain of northern Utah and a few showers over eastern Utah
outside of the forecast area. Between that system and a second one
off the California coast, winds are increasing, becoming breezy
over southern and eastern Utah. Combined with the very dry
conditions across the area, this is resulting in critical fire
weather conditions.

In the wake of the cold front that moved through last night and
this morning, temperatures are noticeably cooler over northern
Utah and southwest Wyoming, with maxes running up to 10F below
what was observed yesterday, but still a few degrees above
seasonal normals. Over central and southern Utah, maxes are
running pretty close to values observed yesterday.

Winds will continue to increase tomorrow as the second trough
moves into the Great Basin, becoming breezy across much of the
forecast area, allowing the threat of critical fire weather
conditions to spread into western Utah. Increasing instability
ahead of the trough will also allow primarily high based
convection to develop over northern Utah and southwest Wyoming
during the late afternoon, persisting through the evening and
possibly the early morning as the trough and associated cold front
move into northern and central Utah.

Cooling with the second cold front will again be most noticeable
over northern Utah and southwest Wyoming, with maxes dropping 5-7F
on Thursday from expected temperatures on Wednesday, putting
those highs near or even just below climo. Southern Utah will see
a few degrees of cooling as well. High pressure is then expected
to rebuild behind the exiting trough beginning late Thursday.


.LONG TERM (AFTER 12Z FRIDAY)...A cooler northwest flow will be
over the eastern Great Basin at the start of the long term period
in the wake of the short wave trof dropping into the plains.

Ridging continues to build back into the Great Basin on Fri and
the airmass starts to warm up again with highs that afternoon a
few degrees warmer than Thu. The threat of any convection is
minimal with only the eastern Uintas having even a small chance
of weak cells.

The ridge moves over the CWA on Sat then weakens somewhat as weak
short wave trofs work into the Great Basin. Med range models start
to struggle with solutions at this point as the features are weak
so the orientation and location of these short wave trofs differ
between models starting Sun. There is a small threat of diurnal
terrain based convection from weak deformation and the 700 mb
thermal ridge Sun thru Tue but confidence in the models is quite
low on determining just where the best threat of this will be. So
kept any pops below thresholds for inclusion in the forecast.


.AVIATION...Northwest winds at the SLC terminal will shift to
southeasterly between 04-05z this evening.


.FIRE WEATHER...A dry westerly flow will persist over the district
through Wednesday. Shortwaves moving through the flow are
enhancing upper level winds, which will result in breezy
conditions across southern and eastern Utah through this evening
and across the majority of the district tomorrow. This will
combine with the very dry conditions to result in critical fire
weather conditions in those areas where fuels are appropriately
dry. Have expanded the Red Flag Warning for tomorrow to include
western Utah zones where winds were not strong enough today.

The strongest wave of the series will move through northern Utah
Wednesday evening into Thursday, bringing a cold front into
northern and central Utah and increasing instability enough for
high based showers and thunderstorms over northern portions of the
district Wednesday afternoon through early Thursday. High
pressure will return beginning Friday, resulting in continued dry
conditions with a warming trend and relatively light winds.


UT...Red Flag Warning until 10 PM MDT Wednesday for UTZ479-482-484-

     Red Flag Warning from 10 AM to 10 PM MDT Wednesday for UTZ478-




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