Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 221736 CCA

Area Forecast Discussion
National Weather Service Flagstaff AZ
1039 AM MST Thu Mar 22 2018

.SYNOPSIS...An approaching low pressure system will bring gusty
southwest winds and mainly rain showers today through midday
Friday. Fair weather will return for the weekend before another
round of unsettled weather early next week.


.UPDATE...Current forecast is on track, with a moist and warm
airmass poised to impact the Northland late today through early
Friday. The high country will see most of the benefit of the
rainfall, with little accumulation expected in the valley
locations due to the relatively weak dynamics of the system. Winds
will be quite strong this afternoon and overnight, especially over
the typical downslope areas north and east of the Mogollon Rim. A
few minor updates were made to increase the precip chances, but
otherwise the current forecast package looks good.


.PREV DISCUSSION /329 AM MST/...An active 24-36 hours in store
weatherwise for northern Arizona as a trough and associated cold
front cross the region. Expect gusty southwest winds to develop
later this morning as the pressure gradient tightens over the
area. Model guidance remains in good agreement showing 700 mb
winds approaching 40-45 kts today and into tonight. This will
generate surface wind gusts up to around 40 mph, with strong
downslope winds continuing during the overnight hours northeast
of higher terrain. Did consider issuing a wind advisory for
portions of the area, but feel cloud cover will inhibit wind
speeds enough to not warrant the advisory. Shower chances will
increase significantly tonight and into Friday morning ahead of
the trough especially along the western Mogollon Rim and Kaibab
Plateau where deep moisture and lift will be maximized. A
relatively warm airmass with this system will keep snow levels
between 8,000-8,500 feet through the duration of the event.
Forecasted rainfall amounts are still expected to be in the
0.25"-0.50" range over higher terrain with lesser amounts over
the lower elevations. The trough will quickly move through the
area Friday morning with precipitation chances decreasing rapidly
from midday onward.

Dry weather will return over the weekend, but a broad trough over
the western United States will generate gusty southwest winds
both days. Latest model guidance continues to indicate the
development of an upper level low over the southwest United States
on Monday potentially bringing a prolonged period of increased
cloud cover, below normal temperatures and slight chances for
showers through the middle of next week.


.AVIATION...For the 18Z package...Predominantly VFR conditions
are forecast under increasing mid and upper-level clouds through
00Z. Expect scattered rain showers to develop near the Kaibab
Plateau after 18Z, before expanding southeast across northern AZ
this evening and overnight. Scattered to numerous SHRA will develop
after 06Z with MVFR/IFR conditions likely over higher terrain and
southwest facing slopes. Winds southwest 20-30 kts gusting 30-40 kts
this afternoon, with localized bands of strong downslope winds
continuing overnight to the northeast of the Mogollon Rim. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...A storm system and associated chance of showers
will move across northern Arizona today into Friday. The best chance
for wetting rain is tonight through early Friday. Snow levels will
remain above 8000 feet for most of this event. Expect strong gusty
southwest winds this afternoon becoming lighter on Friday.

.Saturday through Monday...Expect fair weather Saturday and Sunday
with gusty southwest winds both days. There is a slight chance of
showers Sunday afternoon through Monday. Much cooler weather is
expected Monday.






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