Red Flag Warning 50, NWS Salt Lake City, UT

509 
WWUS85 KSLC 060417
RFWSLC

URGENT - FIRE WEATHER MESSAGE
National Weather Service Salt Lake City UT
917 PM MST Thu Nov 5 2020

UTZ478-492-495-497-061200-
/O.CON.KSLC.FW.W.0050.201106T1900Z-201107T0400Z/
Salt Lake Desert-Central Utah West Desert-
Color Country West Desert-Mojave Desert-
917 PM MST Thu Nov 5 2020

...RED FLAG WARNING REMAINS IN EFFECT FROM NOON TO 9 PM MST
FRIDAY FOR WIND AND LOW RELATIVE HUMIDITY FOR FIRE WEATHER ZONES
478, 492, 495, AND 497...

* AFFECTED AREA...Fire Weather Zone 478 Salt Lake Desert, Fire 
  Weather Zone 492 Central Utah West Desert, Fire Weather Zone 
  495 Color Country West Desert and Fire Weather Zone 497 Mojave 
  Desert.

* WINDS...South winds 25 to 35 mph with gusts to 50 mph in zones 
  492 and 495. South winds 20 to 30 mph with gusts up to 40 mph 
  in zones 478 and 497.

* RELATIVE HUMIDITY...As low as 15 percent.

* IMPACTS...Critical fire weather conditions are expected. Any 
  new fire starts or existing fires may spread rapidly.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Red Flag Warning means that critical fire weather conditions
are either occurring now...or are imminent. A combination of
strong winds...low relative humidity...and warm temperatures can
contribute to extreme fire behavior.

&&

$$

For more information from NOAA/National Weather Service visit...
http://weather.gov/saltlakecity

457 
WWUS85 KSLC 062153
RFWSLC

URGENT - FIRE WEATHER MESSAGE
National Weather Service Salt Lake City UT
253 PM MST Fri Nov 6 2020

UTZ478-492-495-497-070400-
/O.CON.KSLC.FW.W.0050.000000T0000Z-201107T0400Z/
Salt Lake Desert-Central Utah West Desert-
Color Country West Desert-Mojave Desert-
253 PM MST Fri Nov 6 2020

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 9 PM MST THIS EVENING
FOR WIND AND LOW RELATIVE HUMIDITY FOR FIRE WEATHER ZONES 478,
492, 495, AND 497...

* AFFECTED AREA...Fire Weather Zone 478 Salt Lake Desert, Fire 
  Weather Zone 492 Central Utah West Desert, Fire Weather Zone 
  495 Color Country West Desert and Fire Weather Zone 497 Mojave 
  Desert.

* WINDS...South winds 25 to 35 mph with gusts to 50 mph in zones 
  492 and 495. South winds 20 to 30 mph with gusts up to 40 mph 
  in zones 478 and 497.

* RELATIVE HUMIDITY...As low as 15 percent.

* IMPACTS...Critical fire weather conditions are expected. Any 
  new fire starts or existing fires may spread rapidly.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Red Flag Warning means that critical fire weather conditions
are either occurring now...or are imminent. A combination of
strong winds...low relative humidity...and warm temperatures can
contribute to extreme fire behavior.

&&

$$

For more information from NOAA/National Weather Service visit...
http://weather.gov/saltlakecity

Area Forecast Discussion
National Weather Service Salt Lake City UT
944 AM MST Thu Nov 5 2020

.SYNOPSIS...Mild temperatures will continue over Utah and
southwest Wyoming through Friday. A potent storm system is
expected this weekend, bringing a much colder airmass to the area
and the potential for significant precipitation.

&&

.DISCUSSION...Mid level ridging continues to be the dominant
feature locally per morning H5 analysis, while satellite obs
indicate clear skies across the entirety of the eastern Great
Basin within the stable environment. To the southwest a weak upper
low is oriented over the southeastern pacific, while the trough of
note moving forward continues to gain amplitude over the Gulf of
AK. Over the next 24 hours the aforementioned ridge will shift
downstream as a strengthening southwesterly flow aloft will be
punching in from the WSW, and the southeastern pacific low will
open and phase within this flow bringing increased mid/high cloud
cover the local area Friday. Pressure falls in advance of the
PacNW trough will be enhancing a net SE-NW mslp gradient across
the area by Friday afternoon driving increasingly gusty southerly
winds at that time.

The primary forecast challenge through Friday revolves around
increasingly gusty southerly winds, elevated fire weather
concerns (a Fire Weather Watch across the western valleys exists),
and potential for advisory level gusts across the western valleys
Friday afternoon. Thereafter the focus turns to the approaching
weekend trough. Awaiting the full suite of 12z guidance for
decision making.

Going forecast is on track in the near term. Clear skies and
unseasonably warm temps today, with highs spiking to some 15+
degrees above seasonal norms. No updates made or planned.

.PREVIOUS DISCUSSION...On Friday our attention turns to the
impinging storm system that will bring impacts across the state
through the upcoming weekend, and even into early next week. A
trough will dig down the California coast on Friday, accelerating
the southwesterly flow across Utah, especially western Utah. This
dry and breezy weather pattern is expected to result in near-
critical to critical fire weather conditions across western Utah,
where winds will certainly be strong enough, but humidity values
will be marginal. A Fire Weather Watch remains in place there. As
far as winds go, forecast models largely support windy conditions
across western Utah on Friday as surface pressures fall rapidly
over northeastern Nevada ahead of the upper-level low, and 700 mb
wind speeds increase to 40-45 knots. Had this system been earlier
in the year, we would likely have seen most, if not all, of that
momentum aloft transfer to the surface for peak gusts, but now
with the low sun angle and shorter days, the amount of mixing we
can expect is a bit more limited. Nevertheless, wind gusts over
western Utah are likely to reach 40 mph, it's just a question of
whether we'll see gusts of 45+ mph for a possible Wind Advisory.
Will continue to monitor that potential. Temperatures will remain
very warm, especially with the better mixing in the northern Utah
valleys ahead of the front; in fact, there is a chance that SLC
will make a run a the daily and monthly record high temperature of
75 degrees on Friday, with the current forecast at 74F, and about
a 20% of meeting or exceeding 75 degrees. Temperatures will
likely remain somewhat mild Friday night as breezy conditions
continue ahead of the front.

By Saturday, increasing diffluence aloft ahead of the upper-level
low will help support scattered shower coverage across the state
Saturday morning. By Saturday afternoon, a lobe of vorticity
rounding the trough will help to swing it northeastward across
Utah through Saturday night, while driving the surface cold front
across the region. The combination of the upper-level forcing and
increasing baroclinicity along the front will support an area of
moderate precipitation moving across western to northern Utah.
The strongest cold advection will likely behind this area of
precipitation, thus most lower elevations will see this come
through as rain, but with a chance of switching over to snow
as precipitation winds down and becomes more showery under the
upper-level low into Sunday morning. While some light snow
accumulations possible to around 5000 feet, most snow
accumulations will in the mountains above about 6500 feet, where
about 4-8 inches of snow are possible through Saturday night.

Model trends continue toward a slower and less organized
system...at least initially. To start the long term forecast
period, the first shortwave associated with a longwave trough
across the West will be lifting into the central Rockies and High
Plains. Expect showery conditions will continue across the state
through Sunday afternoon as the next shortwave digs southward
toward southern Nevada.

While this shortwave is digging into southern Nevada, a 140kt+ jet
maxima will be colocated with at least a period of frontogenesis
across central and southern Utah. This may support a period of
widespread precipitation from roughly I-70 south Sunday into Monday
until the shortwave begins lifting into the central Rockies.

700mb temperatures will be fairly cold, with snow levels near 4500-
5000 feet across southern Utah. Expect moderate snow accumulations
across the mountains of Utah...mainly south of I-80. Some locations
in the central and southern mountains may see up to a foot from
Sunday afternoon into Monday morning. Some variance of this solution
has been consistently in a significant portion of the ensemble
systems for several days, so confidence continues to increase in
this portion of the forecast.

Regardless of any precipitation chances...it will remain quite cold
compared to temperatures the previous week through the entire long
term forecast period, with temperatures averaging 10-20 degrees
below normal.

&&

.AVIATION...VFR conditions are expected at KSLC through the valid
TAF period. Southeast winds will become northwest between 19-20Z.
Northwest winds are expected to remain light through 03Z, then
switch to the southeast. Cloud cover is expected to decrease during
the evening.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Fire Weather Watch from Friday afternoon through Friday evening
     for UTZ478-492-495-497.

WY...None.
&&

DISCUSSION/AVIATION...Merrill/Verzella
PREVIOUS DISCUSSION...Church/Kruse

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

Hazardous Weather Outlook
National Weather Service Salt Lake City UT
532 AM MST Thu Nov 5 2020

UTZ001>016-019>021-517-518-WYZ021-061245-
Cache Valley/Utah Portion-Northern Wasatch Front-
Salt Lake and Tooele Valleys-Southern Wasatch Front-
Great Salt Lake Desert and Mountains-Wasatch Mountain Valleys-
Wasatch Mountains I-80 North-Wasatch Mountains South of I-80-
Western Uinta Mountains-Wasatch Plateau/Book Cliffs-
Western Uinta Basin-Castle Country-San Rafael Swell-
Sanpete/Sevier Valleys-West Central Utah-Southwest Utah-
Utahs Dixie and Zion National Park-South Central Utah-
Glen Canyon Recreation Area/Lake Powell-Central Mountains-
Southern Mountains-Southwest Wyoming-
532 AM MST Thu Nov 5 2020

This Hazardous Weather Outlook is for the western two thirds of
Utah and southwest Wyoming.

.DAY ONE...Today and Tonight

No widespread hazardous weather expected.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Critical fire weather conditions may develop Friday due to gusty
winds and low humidity expected ahead of a strong cold front
passage on Saturday.

The storm system will make its way through the area Saturday into
early next week. Much colder temperatures are anticipated by
Sunday, with highs in excess of 20F below seasonal normals. The
system will also bring precipitation, with snow down to all but
the valleys are far southern Utah. Significant snow is possible
for the mountains, with the highest chance of significant snow
anticipated for central and southern Utah. The system is expected
to exit Monday, with cool and unsettled conditions continuing
through at least midweek.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information
about observed severe weather to the NWS while following all
local, state, and CDC guidelines.

For more information from NOAA/s National Weather Service visit...
http://weather.gov/saltlakecity

For information on potential road travel impacts visit...
http://www.udottraffic.utah.gov/roadweatherforecast.aspx