Scientific Forecaster Discussion
fxus65 kfgz 212211
Area forecast discussion
National Weather Service Flagstaff Arizona
311 PM MST Thu Nov 21 2019
Synopsis...periods of rain and snow will continue through
tonight. Showers will decrease overnight from west to east and
move out of Arizona Friday afternoon. Drier and warmer weather
will begin to develop later on Friday and last through the
Discussion...the cold low continues to sit over the Las Vegas
area. Models have it beginning to move out to the east this
evening. A band of showers and thunderstorms extends from the
Kaibab plataea south-southeast to Wickenburg Arizona with the
thunderstorms on the south end of the line. The cold air aloft and
diurnal heating in the desert area is providing the increased
instability to form some strong storms over the desert. Have kept
some thunder in the forecast due to the instability along and
south of the Mogollon Rim, and across Yavapai and western Coconino
counties through this afternoon. The band of snow showers is
producing areas of heavy snow and poor visibility as it moves
across Coconino and northern Yavapai counties with snowlevels
dropping to 5000 ft under the showers. Look for another possible
band of shower activity to move through the region this evening as
the upper-level low moves east.Rain and snow decreases west to
east behind this low with the last few shower over the chuska and
White Mountains ending late Friday afternoon.
The shortwave trough that drops down off the low moving into
Vancouver Canada cuts off and drifts south to settle off Southern
California. This cutoff low stays in place until late Tuesday
when the next deep trough out of the Gulf of Alaska picks it up
and pulls the moisture it picked up sitting off the coast over the
Desert Southwest. This looks very similar to the current system
with the potential to bring another round of heavy precipitation
to the area, rain to the lower elevations and snow to the high
country. It's too early to tell how much we will get from this
system, but this is definitely a weather system to watch,
especially with the Holiday travel. If you have to travel next
week, it's best to plan for the worst. Stay tuned as we will keep
you updated as this system develops.
Aviation...for the 00z package...a storm system will move across
Arizona overnight then out of the area on Friday. Areas of rain and
snow showers will continue through 06z then decrease in coverage.
Snow levels around 6000 feet above mean sea level. Expect MVFR
conditions across much of northern Arizona with LIFR conditions
possible in showers over the higher terrain, especially south and
west of a kpga-kinw-ksjn line. Mountains in the region will be
obscured at times. VFR conditions returning to the area after 14z.
Aviation discussion not updated for taf amendments.
Fire weather...rain and snow showers will end from west to east
overnight. Friday and Saturday will see light winds, warmer daytime
temperatures and clearing skies. Generally poor ventilation through
the period. Strong inversions and drainage flow are likely to
develop Saturday morning.
Sunday through Tuesday...mostly clear skies, light winds and warmer
daytime temperatures will continue Sunday. Monday will see gusty
westerly winds pick up with a slight chance of rain and high
elevation snow showers Monday night into Tuesday.
Fgz watches/warnings/advisories...Winter Weather Advisory until
7 PM MST this evening for azz004-006-007-015-016.
Winter Storm Warning until 11 PM MST this evening for azz017.