Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 201541

Area Forecast Discussion
National Weather Service Flagstaff AZ
841 AM MST Tue Mar 20 2018

.SYNOPSIS...Dry weather and warming temperatures are forecast
through mid week, with increasing clouds later today and
Wednesday. On Thursday and Friday, gusty southwest winds and good
chances for mainly rain showers are forecast as the next low
pressure system impacts the area. Fair weather is expected to
return for the weekend.


.DISCUSSION...Mid and high level clouds will increase over the
next 24 hours as a large plume of Pacific moisture streams into
southern California/Nevada. A weak ridge of high pressure will
keep precipitation to the northwest through Wednesday with
light winds and above normal daytime temperatures for northern
Arizona. Ridging will shift east later Thursday into Friday as a
weak trough pushes into the region. This feature will generate
mainly rain showers with snow levels above 8000 feet. However,
showers will likely be tied closely to the terrain with only light
rain in the lower elevations. The trough will quickly move
through Friday afternoon with diminishing showers and clearing


.PREV DISCUSSION /353 AM MST/...Today and Wednesday - weak ridging
develops over Arizona with daytime temperatures warming to above
normal. There will be increasing clouds starting later today as
our area will be on the southern edge of a large subtropical
moisture plume (atmospheric river) that will be bringing rain to
much of California. Late Thursday and Friday - the moisture plume
shifts into Arizona along with a weak trough passage. Windy
conditions are possible Thursday ahead of the trough, with a good
chance of rain showers Thursday night into Friday. At this time,
snow levels look to remain above 8000-8500 feet, possibly even
higher. Overall, model precipitation forecasts have decreased over
the past few runs for northern Arizona, with most guidance
pointing to amounts of 0.20"-0.40" for the mountains 0.20" or less
for lower elevations. However, the amount of available moisture
combined with a strong upslope component suggest some locally
higher amounts over the favored southwest slopes. The main thing
limiting the higher amounts will be the short duration of the best
combination of moisture and orographic lift. After the moisture
shifts east of the area by Friday night, Saturday through Monday
look fair with near normal temperatures.


.AVIATION...For the 18Z package...Look for VFR conditions under
increasing mid- to upper-level cloudiness over the next 24 hours.
Light winds generally less than 10 kts. Aviation discussion not
updated for TAF amendments.


.FIRE WEATHER...High pressure moving into the southwest will bring
dry and warmer weather with light winds through Wednesday. However,
clouds will increase in advance of an approaching Pacific weather
system. Ventilation will be fair to good each afternoon.

Thursday through Saturday...Expect increasing southwest winds and
moisture across Arizona as a weather system moves across the area.
Thursday and Friday will see the best chance for rain showers, along
with gusty southwest winds. Temperatures cooling to near
average for this time of year on Friday and Saturday.






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