Scientific Forecaster Discussion
fxus65 kslc 282133
Area forecast discussion
National Weather Service Salt Lake City Utah
333 PM MDT Wed Jun 28 2017
Synopsis...a shallow boundary will continue to sag south across
the area over the next 24 hours. High pressure will return
beginning Friday. A weakening trough will cross namely northern
Utah Sunday prior to high pressure rebuilding once again early
Short term (through 12z saturday)...the axis of the cool upper
trof over the nrn rockies extends thru central Idaho into nern Nevada
this aftn. A dry west to southwest flow is over the County Warning Area ahead of
this trof and has brought gusty west to southwest winds to the
County Warning Area.
Convection has formed along the Idaho border closest to the best trof
dynamics and a few small cells formed over the western Uinta Basin.
This convection over the north will continue into the evening ahead
of the trof axis but should end quickly once the trof passes.
An associated dry cold front has moved into nwrn Utah and will
reach central Utah by this eve then stall across srn Utah overnight.
This brings a cooler airmass into the north and keeps Post frontal
northwest winds going over the northwest into this evening.
A trailing short wave in the nwly flow aloft clips nrn Utah on Thu
tightening the nwly gradient across the County Warning Area and generating gusty
NW winds in the ern valleys. Temps Thu will be 5-10 deg cooler
across the north from today but stay warm south.
The upstream ridge in the ern pac shifts into the Great Basin Thu
night and Fri bringing lighter winds and a more stable airmass to
Utah. Temps across the north start to rebound on Fri.
Long term (after 12z saturday)...a low amplitude and splitting
trough translating east across the western Great Basin Saturday
will shift the interior ridge downstream of the area, but
dry/stable conditions will continue for most all areas outside of
the prone mtn spines where isolated terrain based convection is a
potential. A net warming trend will continue beneath a modest
southwesterly flow aloft with temps pushing 5+ above seasonal
The northern portions of the weakening open wave trough will slide
across far northern Utah Sunday, with modest mid level cooling at
h5, but limited cold air advection below that level. Lacking significant
moisture/forcing, do not expect much more than isolated and
largely terrain based convection focused over the north come
midday Sunday, largely driven by diurnal instability and the
aforementioned steepening of mid level lapse rates.
Upper level ridging will once again rebound in wake of the trough
passage early next week, this allowing temps to trend a little
warmer each day through midweek. Do not foresee suitable
conditions for convection of any significance attm, but have left
some token pops over the prone northern mtns.
Aviation...VFR conditions will prevail this evening at kslc as PM
convection should remain well north of the terminal. Northerly
winds, at times gusty, will persist through the evening before
either switching to the southeast or becoming light and variable
Fire weather...a Bone dry airmass, warm temperatures and gusty
winds will keep fire weather conditions critical across southern
Utah along with portions of central and ern Utah into this
evening. A dry cold front will cross northern Utah this afternoon
then central Utah tonight with gusty winds on both sides of the
front maintaining critical conditions for most of the remainder of
the area into this evening. Existing red flag warnings for much
of the fire district remain in effect.
Scattered thunderstorms will continue along the Idaho border
through mid evening then end. These will have some moisture with
them, but also will produce lightning and gusty erratic winds.
Winds Thursday look to remain strong enough across portions of
eastern and far southern Utah to produce critical fire weather
conditions again in these areas and the red flag warning has been
extended for these areas through Thursday evening.
A cooler airmass will spread into the northwestern portions of
the area on Thursday bringing slightly higher relative humidity. Winds are also
expected to not be quite as strong in this area. A more stable
airmass and lighter winds will lower conditions below critical
levels in all areas on Friday.
Utah...red flag warning until 10 PM MDT Thursday for utz482-484-488-489-
Red flag warning until 10 PM MDT this evening for utz478-479-492-
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