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fxus65 kslc 192147 

Area forecast discussion
National Weather Service Salt Lake City Utah
347 PM MDT Thu Sep 19 2019

a storm system will move through the area late today through
Friday. The associated cold front will work east across the area
through tonight. The cooler temperatures and precipitation across
northern Utah Friday will be followed by drier and milder
conditions this weekend.


Short term...
an upper-level low continues to slowly pivot through Nevada this
afternoon. Gusty southwesterly winds continue across much of
southern and western Utah late this afternoon and into the early
evening ahead of the trough. A pre-frontal trough had pushed into
central Utah this morning where it turned winds to the northwest
and stalled. Meanwhile the cold front is pushing into northwest
Utah late this afternoon, marked by temperatures dropping off
quickly through the 60s and into the 50s already at Wendover. The
cold front will make its push across Utah in earnest tonight,
ushering in much cooler temperatures for Friday.

A lobe of vorticity will round the base of the trough early
Friday morning and eject along the frontal boundary through
northern Utah. Expect numerous to widespread showers to develop
across northern Utah Friday morning as the wave ejects across the
area. Furthermore, as the cold pool aloft moves over northern Utah
by mid-morning, steep lapse rates and abundant moisture under the
cyclonic flow aloft will support continued showers, with lake
enhancement favored east of the lake. Time of day is perfect for
lake enhancement, as the land breeze circulations over the Great
Salt Lake will favor convergence over the lake, while lake induced
equilibrium heights climb to 20kft. These conditions also make it
possible for waterspout development over the lake. Westerly flow
under the base of the trough will help direct lake enhanced
showers along the northern Wasatch front in Davis County. There is
some signal in the high resolution models for this enhancement,
with the href giving 20-30% probabilities over an inch of rainfall
along the terrain in Davis County. Also, snow levels will drop to
around 8000 feet, with 1 to 3 inches of accumulation possible
above this in the Wasatch and uintas.

Otherwise, morning rain will generally taper off behind the
shortwave passage. However, given the steep lapse rates and
moisture under the upper-level trough, expect to see scattered
afternoon showers and thunderstorms redevelop. Any morning lake
enhancement will become disrupted as the morning convergence over
the lake flips to divergence with the developing lake breeze
circulation as the land surface heats, leaving a Lake Shadow. Any
midday or afternoon showers and thunderstorms will be capable of
producing cold air funnels, and small hail/graupel. Cold air
funnels rarely reach all the way to the ground, and thus are
typically not a treat.

In the wake of this storm system, high pressure will build in
bringing dry conditions and milder/warming temperatures through
the weekend.

Long term...
ensemble signals are beginning to point more and more towards a
similar idea to latest deterministic ec regarding early week
trough evolution across the Great Basin during the Mon-Tue
timeframe. Namely, an open wave upstream becoming closed over
Nevada Monday, then cut off while slowly translating south into
the Desert Southwest Tuesday into midweek. Details regarding
extent of sub-trop moisture tap in advance and advection of this
into largely southern portions of the forecast remain a lower
confidence forecast however. With this, have followed a similar
trend as the previous forecast focusing highest pops over the
south/southwest Monday, while allowing for a more rapid drying
trend north-south overnight into Tuesday.

Thereafter the most likely scenario maintains a dry northerly flow
into late week, prior to backing aloft in advance of yet another
(and potentially deeper) longwave trough Friday on.


gusty northwesterly winds will be maintained at the kslc terminal
this afternoon, with a 60% chance of gusts in excess of 30 mph
periodically through 00z. Cigs are anticipated to fall to or below
6000ft above ground level after 08z Tuesday morning, with increasing showers for
the morning hours.


Fire weather...
strong and gusty south-southwest winds across much of central,
southern and eastern Utah this afternoon ahead of a cold front
will diminish and turn to the northwest behind the frontal passage
tonight. These winds will combine with low humidities to create
hazardous fire weather conditions where fuels are critically dry.
Behind the cold front, precipitation, with snow above around 8000
feet, will gradually fill in across mainly northern and central
Utah this evening and into Friday morning. Much cooler
temperatures will follow the front. Drier conditions will develop
for the weekend, with southwest flow increasing a bit on Sunday
ahead of the next storm system.


Slc watches/warnings/advisories... flag warning until 10 PM MDT this evening for utz489-492-494-



long term...Merrill

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