Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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FXUS65 KSLC 260850

Area Forecast Discussion
National Weather Service Salt Lake City UT
250 AM MDT Mon Jun 26 2017

.SYNOPSIS...High pressure aloft will shift east today, allowing a
mild southwesterly flow to develop across the region by afternoon.
A cooling trend will begin on Tuesday and continue through
midweek. High pressure aloft will return for the end of the week.


Water Vapor Satellite shows a ridge overhead with weak a shortwave
riding into northern Utah. A small closed low was off the northern
California coast, while a deeper and broader system is affecting
British Columbia. 400-200mb MDCARS wind observations place an
anticyclonic 75-105kt jet from British Columbia into the north
central Plains. A 50-80kt subtropical westerly jet was nosing into
California from the Eastern Pacific. GOES/SLC 00Z RAOB/HRRR
indicate that precipitable water values vary from 0.20"-0.33"
mountains to 0.35"-0.65" valleys.

Southwest winds will increase from Delta to Kanab and southwest
today in response to a developing southerly gradient with a
cyclone near Wendover. It will remain warm and quite dry today in
advance of a cold front.

However SPC SREF guidance suggests modest destabilization, with
BUFKIT forecast soundings suggesting LCL near 500mb. This equates
to near 1500 J/kg DCAPE and a very low probability of measuring
rainfall. So, while kept scattered thunderstorms for the
mountains, in the valleys opted to go with unmentionable PoPs with
Isolated Dry Thunderstorm with gusty winds wording. This carries
on across much of the state this evening before exiting to our
northeast tomorrow morning.

Shallow cold front makes it to about Interstate 70 tomorrow as the
aforementioned subtropical jet noses in with a stronger wave
crossing Idaho. Westerly winds will likely become gusty across the
eastern valleys. The convective threat diminishes with many
locations seeing cooler temperatures.

Utilized the Average Vertical Smoke Integration from our Air
Quality Forecast Guidance to show a shift in the visible smoke
from southern Utah today to northeast across central Utah and as
far north as SLC and the Uinta basin tonight.

Heading into Wednesday, Utah and southwest Wyoming remain on the
southern fringes of the longwave trough positioned over the
Pacific Northwest and Great Plains. The western portion of this
trough begins sagging southward through the day Wednesday, helping
to push a cold front into northern Utah. Some mid-level moisture
also moves into the area with this wave, so shower/thunderstorm
formation is possible across the northern portions of the CWA late

Cold advection northwesterly flow continues into Thursday, cooling
temperatures even more across the northern half of the CWA. After
the initial wave Wednesday, the airmass begins to dry out again,
though isolated mountain convection can`t be ruled out Thursday and

The larger trough looks to push east of the Rockies late Thursday
into Friday, with a ridge building over the southwestern CONUS for
the end of the week. However, this ridging looks to be short-lived,
as the global models show a shortwave trough moving off the Pacific
and into the Great Basin on Saturday. Have increased POPs a bit for
Saturday, especially in the mountains and far northwest Utah, to
account for this impinging shortwave. Exactly how this disturbance
evolves and tracks through the area is low confidence, however, as
agreement in the models begins to break down considerably late
Saturday through early next week.


Winds at the SLC terminal are expected to switch to the
northwest around 20-22Z, with a slight chance that the switch occurs
as early as 19Z. Isolated showers and thunderstorms are possible
across northern Utah this afternoon/evening, with gusty and erratic
winds as the most likely impact.


ERC values have risen to between the 80th and 96th percentile
across southern and central Utah. Northeast Utah remains below
50th percentile, but the remainder of northern Utah is climbing
above the 50th percentile.

Multiple concerns regarding fire weather. The Haines index will
be a 6 today across the region, remaining so across southern Utah
for the rest of the week. Haines will fall to between 4-5 across
much of northern and central Utah beginning tomorrow.

Gusty southwest winds develop across west central, southwest and
south central Utah today prompting a Red Flag Warning due to many
locations seeing single digit RH as well. Believe a few locations
across northern Utah will see localized critical fire weather
conditions due to wind and RH. The other threat today is from
isolated dry thunderstorms, potentially starting new fires due to
lightning, and fanning existing fires due to strong gusty/erratic
dry microburst winds.

Tomorrow the gusty wind threat shifts to the eastern valleys with
valleys being dry enough to consider fire weather as critical
where fuels are. Showers and storms should no longer be a threat
by afternoon. It will be a little cooler and not quite as dry with
the passage of a cold front for most places.

It will remain dry Wednesday through the weekend, with
temperatures only gradually moderating. Wednesday it may remain
gusty enough to provide critical fire weather conditions along the
Arizona border. Little to no shower and thunderstorm activity is
expected for the remainder of the week.


UT...Red Flag Warning from noon today to 10 PM MDT this evening for




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