Area Forecast Discussion
Issued by NWS Flagstaff, AZ
FXUS65 KFGZ 201301
Area Forecast Discussion
National Weather Service Flagstaff AZ
600 AM MST Fri Jan 20 2017
.SYNOPSIS...A series of winter storms will affect the region
through early next week. These will be cold systems, with heavy
accumulations of snow across the high country. Hazardous driving
conditions should be anticipated for the next several days.
.DISCUSSION...The first in a series of winter storms arrived late
Thursday afternoon and brought rain and snow to much of the area
overnight. This storm moved well east of the state this morning.
However, the saturated layer remains unstable and upslope showers
have persisted. This regime will continue for much of the morning
before deeper moisture and forcing arrives arrives ahead of our next
storm, still located in the eastern Pacific.
There may be a brief period between 6AM-8AM MST where the upslope
showers along the Mogollon Rim are enhanced by a seeder-feeder
process. This process is driven by a small area of mid-level warm
advection, noted ahead of the next low.
This next storm has a much larger wavelength and longer fetch of
unstable and moist air compared to the system last night. We expect
a larger area to be affected and QPF values to be on the order of 2
to 3 times what was observed overnight.
Rain and snow amounts will be prolific tonight and the Winter Storm
Warning will continue. This is a dangerous storm, only travel if
Precipitation will slowly taper off from west to east during the day
Saturday. There will likely be another unstable and saturated
upslope layer to contend with, which will prolong some shower
activity in the higher terrain. We have extended the Winter Storm
Warning all the way through Saturday in the eastern zones as a
Hghts rise Saturday night and early Sunday ahead of yet another
Pacific storm system due late Sunday and Monday. Details are now
becoming more clear concerning this system and it looks like it will
be just as serious as the storm approaching for tonight.
The is some debate concerning the development of warm advection
precipitation ahead of the low Sunday afternoon, but by Sunday night
and Monday, most models now agree on moderate to high levels of QPF
and strong winds. We have boosted POPs and snow amounts, stay tuned.
A cold and unstable airmass will trail the third storm well into the
middle of next week. Expect a drying trend with some mountain snow
showers by this time, with very cold temperatures.
.AVIATION...For the 12Z package...Expect widespread MVFR conditions
and areas of IFR/LIFR conditions in occasionally heavy rain and snow
showers through the next 24 hours across northern Arizona. Aviation
discussion not updated for TAF amendments.
Winter Storm Warning above 5500 feet until noon MST Saturday for
Winter Storm Warning above 5500 feet until 6 PM MST Saturday for
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