Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

000
FXUS65 KSLC 182150
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
350 PM MDT Sun Jun 18 2017

.SYNOPSIS...High pressure continues to build over the eastern
Great Basin today and will remain in place Monday into Wednesday,
bringing very hot temperatures to the region. A very dry airmass
remains in place through early in the week before temperatures
cool slightly.

&&

.SHORT TERM (Through 06z Thursday)...High pressure continues to
build over the West this afternoon, resulting in mostly clear skies
over the forecast area this afternoon. The airmass continues to dry,
with satellite derived PWs showing most valley locations in the 0.4
to 0.6 inch range and lower values for the mountains. Temperatures
are a bit warmer than yesterday over northern Utah and southwest
Wyoming, with maxes running near or slightly above seasonal normals.
Meanwhile, temperatures over southern Utah are just a bit cooler
than yesterday with the influence of the front, but maxes are still
running around 10F above seasonal normals.

The ridge will continue to build during the early part of the week,
with the axis moving overhead by tomorrow afternoon. Temperatures
will warm significantly over the next couple of days, with maxes
running in excess of 15F over climo over northern Utah and more than
20F above climo over southern Utah. Temperatures will be near or
above record values across many locations across the area, with
temperatures becoming dangerously warm over southern Utah. Going
Heat Advisories and Excessive Heat Warnings cover the threat well
and did not make any changes.

Monday will be dry and stable with little threat of showers and
thunderstorms. However, some shortwave energy is expected to move
into the ridge by Tuesday, with enough moisture to produce a few
thunderstorms over the higher terrain. By Wednesday, the ridge is
expected to flatten in response to a trough diving south into the
Pacific Northwest. This will bring an initial boundary into northern
Utah that will cool temperatures a bit as southern Utah remains
dangerously hot. In the 12Z runs, GFS is still a bit faster with the
front and associated colder air than the ECMWF, but seems to have
moved slightly toward the slower solution.

.LONG TERM (After 06z Thursday)...With the shortwave boundary
moving south through Utah into Thursday, the jet axis drops south
and east through the northern Rockies as the flow aloft turns to
northwesterly. Models continue the mention of moisture across the
forecast area, hinting that terrain driven convection may be
possible under this flow pattern. As the trough compresses the
ridge into Friday, remaining well to the north and east of our
area, a deformation zone develops farther west over California.
This may generate some increase in winds during the afternoon
hours Thursday and Friday as the surface pressure gradient becomes
convergent from northwest to southeast. Have kept mention of
mainly high elevation showers and thunderstorms in the extended
period, as very little has changed from the previous model runs.

Regarding the very hot temperatures in place earlier in the week,
little day to day change is expected through the remainder of the
week however a slight cooling trend will be in place.

The big picture pattern that global models are advertising is for
high pressure to build back in and strengthen across the desert
southwest by Friday and into the following weekend. The GFS looks
to be a faster solution, while the EC hints at a shortwave digging
southward into Wyoming and Colorado while the GFS pushes it
farther to the east and building the ridge over California.

&&

.AVIATION...Northerly winds will continue at KSLC through the
evening before switching back to the south during the 03-04Z
timeframe. VFR conditions will prevail through the TAF period.

&&

.FIRE WEATHER...High pressure is starting to build over the West
today and will become the dominant feature over the fire district by
tomorrow. This will result in dry conditions with light winds and
hot temperatures for the first part of the week. The airmass will be
quite stable on Monday but some weak instability will move in
Tuesday, introducing the possibility of high based thunderstorms
over the higher terrain. With strong heating, a Haines Index of six
is forecast for the southern half of Utah tomorrow through much of
the week. The ridge is expected to flatten Wednesday ahead of a
mostly dry cold front that will move through the district Thursday,
providing some relief from the heat.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Heat Advisory from noon Monday to 10 PM MDT Thursday for UTZ013-
     020.

     Excessive Heat Warning from noon Monday to 10 PM MDT Thursday
     for UTZ019-021.

WY...None.
&&

$$

SHORT TERM/FIRE WEATHER...Traphagan
LONG TERM...Dewey
AVIATION...Seaman

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



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.