High Wind Watch 1, NWS Flagstaff, AZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
914 AM MST Sat Feb 17 2018

.SYNOPSIS...Expect dry and warmer conditions today, ahead of a
cold storm system due on Monday. This storm will bring strong
southwest winds to our area Sunday afternoon through Monday, with
a good chance of rain and snow showers Monday and Tuesday.
Tuesday could be the coldest day so far this season.

&&

.UPDATE...
Several things to consider this morning.

For today, satellite imagery reveals low clouds and fog along
I-40 from Holbrook to the NM line, and in the vicinity of Hwy 61
north of St Johns and will update the forecast to keep this around
through mid afternoon. Elsewhere fair weather today.

Sunday and Monday, the system to affect the northland these days
in significant, with gusty southwest winds developing sunday
afternoon and peaking in speeds Monday. We will likely be issuing
a Wind Advisory starting Sunday afternoon for much of the area
along and north of the Mogollon rim. Wind products for Sunday
night need a closer look as winds should decouple across the
Little Colorado River (LCR) but continue across the higher
terrain. For Monday, as it stands now the LCR should be seeing
SW wind gusts from 55 to 65 mph for several hours. Should todays
12z progs continue to show this, we will be issuing a High wind
watch for at least the LCR.

With rain and snow showers developing Sunday night and Monday and
couple with the winds, we will also be considering what type of
winter weather products to issue for the high country.

Today is a great day to prep for this weather.

&&

.PREV DISCUSSION /440 AM MST/...Dry and mild conditions are
expected today as above normal hghts exist across the southwest.
Mainly dry conditions are anticipated Sunday as well, although
winds and clouds will begin to increase, ahead of a deep and cold
trough due on Monday.

Models have trended a bit further westward with this trough as it
enters the Great Basin. This allows the system to tap into the
deep moisture that still persists over southern Arizona and
northern Mexico. This moisture will move north Sunday night as
southwest flow increases, leading to upslope shower development
well ahead of the main cold front.

By Monday, strong southwest winds will have developed over much of
the region, with upslope shower activity in full swing. A cold
front will also drop southeast across the area, with showers
enhancing for a few hours along the front. Finally, much colder
and unstable air will trail the front, with instability showers
lingering into Tuesday.

This will be a very cold system and snow ratios will be high.
Small changes in the path of this storm could cause the the
interaction with the sub-tropical moisture plume to fail and
bring QPF values way down. Conversely, tracking a bit farther
westward could cause the QPF values to go way up. This is
indicated by a large variance in model forecast QPF at the
moment, we have taken a path in the middle of the road for now.
Bottom line, expect very cold and wintery conditions by Monday
and Tuesday.

Conditons dry and warm by the middle of the week, with a
possibility of more showers by the end of the week.

&&

.AVIATION...For the 18Z Package...Mostly clear skies are expected
today, with increasing upper level clouds after 00Z Sunday. Winds
generally 10 kts or less today and tonight. Aviation discussion
not updated for amendments.

&&

.FIRE WEATHER...Expect fair weather with slightly above normal
daytime temperatures and light southwest winds today. On Sunday,
gusty southwest winds return as a strong cold front approaches from
the northwest.

Monday through Wednesday...The cold frontal passage is expected
Monday, with wind gusts currently forecast from 40 to 55 mph,
fastest speeds along and north of the Mogollon Rim. Precipitation
chances will increase especially across the higher terrain Monday.
Colder and drier weather is expected Tuesday and Wednesday.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

PUBLIC...DL/Peterson
AVIATION...RR
FIRE WEATHER...KD

For Northern Arizona weather information visit
weather.gov/flagstaff