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 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS65 KSLC 170937
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
337 AM MDT Tue Oct 17 2017

.SYNOPSIS...A warming trend will continue through the middle portion
of the week while a weak disturbance crosses the area Wednesday
night through Thursday. A stronger storm system is forecast to cross
the area Friday.

&&

.SHORT TERM (THROUGH 12Z FRIDAY)...An upper ridge remains in place
this morning, with some thin high clouds drifting across the area.
The ridge will weaken this afternoon as a weak shortwave disturbance
approaches the area. Southwesterly flow aloft will increase a bit,
allowing for warmer temperatures, particularly in valley areas, as
mixing will improve slightly. Otherwise, dry and stable conditions
will persist today and tomorrow.

The southern end of the shortwave disturbance is now more
consistently forecast by the models to strengthen across southern
Nevada and northwest Arizona tomorrow. It is then forecast to lift
northeast across Utah tomorrow night into Thursday. Although
moisture will increase with this disturbance, given the dry lower
levels currently in place, valleys will be hard pressed to receive
much in the way of precipitation. However, have increased PoPs to
allow for slight chance wording of PoPs across the higher terrain.
Although this system will be accompanied by increased cloud cover
and a slightly cooler airmass on Thursday, better mixing as
southwesterly flow strengthens again should keep temperatures on the
warmer side and above normal for most areas.

.LONG TERM (After 12z Friday)...The Pacific Northwest trough
continues to evolve with the latest model guidance for late in the
week. The overall trend continues to be a warmer and drier
(relatively) weather system to impact Utah and southwest Wyoming.

As the cold front moves through Utah and southwest Wyoming Friday
afternoon (with both the surface gradient and the 700mb baroclinic
zone), the best window for precipitation looks to be Friday
afternoon and early evening. With this forecast package the PoP
forecast was aimed to display this time period better for
precipitation chances. As latest model guidance has come available,
both extended global models are trending more north with the trough
and thus the best dynamics are trending more north of Utah, as well
as a downward trend in precipitation amounts. The cold pool aloft
remains farther north in the core of the trough while the 700mb
baroclinc zone becomes a bit less organized as it progresses through
Utah late Friday. With the best timing for precipitation Friday
evening, snow levels cool to near 6300 feet or so. While the axis of
moisture quickly rotates eastward, the cold air aloft continues to
settle in across northern Utah.

Models have agreed fairly well on the exit of this trough Saturday
as warm advection and significant rising heights build in behind the
departure of the upper level trough. Some mid-high level moisture is
still evident in the guidance, though very little dynamics support
any chance of precip for the weekend and going into early next week.
Temperatures warm again to near seasonal normal going into the
extended period as high pressure builds across the region.

&&

.AVIATION...VFR conditions will prevail with minimal operational
weather concerns at the KSLC terminal through the valid TAF period.
Southeasterly winds currently in place are expected to shift to the
northwest between 18z-19z today, with a return to the southeast
between 03-04z.

&&

.FIRE WEATHER...High pressure over the area this morning will weaken
by mid-afternoon as a weak disturbance approaches. This will bring a
modest increase in southwesterly flow aloft, otherwise dry and
stable conditions will persist today. Humidities will remain on the
low side, although they should rise slightly from yesterday`s
values.

The southern extent of said weak disturbance is expected to
strengthen across southern Nevada and northern Arizona on Wednesday,
then lift northeast through Utah on Thursday. Wednesday will remain
fairly dry and stable, but by Thursday, light rain with snow above
around 11000 ft will be possible. Despite increasing humidities,
chances of wetting rain will be near zero.

Southwest flow will increase again late Thursday into Friday ahead
of the next storm system, which will push a fast-moving cold front
through the fire district Friday through Friday night. A quick burst
of valley rain and mountain snow can be expected, mainly across
northern and central Utah, with this front. High pressure will then
rebound Sunday through the early part of next week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

Cheng/Dewey

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.