Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 171648

Area Forecast Discussion
National Weather Service Flagstaff AZ
948 AM MST Sun Dec 17 2017

.SYNOPSIS...An area of low pressure south of the southern Arizona
border will bring scattered snow showers to the eastern Mogollon
Rim and White Mountains today through Monday. Scattered light
rain showers will be possible in southeastern Yavapai and
northern Gila counties. Drier and warmer conditions will develop
Tuesday and Wednesday, ahead of a strong cold front due Thursday.


Update this morning mainly tweaks chances of precipitation and
snowfall amounts to better align with radar and model trends.
Otherwise no significant changes concerning timing of this
system, and subsequent impacts.


.PREV DISCUSSION /535 AM MST/...A vigorous upper low, about 200
miles southwest of Tucson this morning, will slowly move east
along the southern Arizona border through Monday afternoon. Bands
of showers and embedded convection will rotate into central and
eastern Arizona through the same time period. Very dry air over
central and northern Arizona will limit QPF values and easterly
streamlines will limit moisture transport anywhere north of the
I-40 corridor.

Most meso-scale models indicate a band of showers moving north
through Phoenix and into the southern portions of our CWA this
morning. This will likely be the most organized band, as well as
the best chance of light snow accumulations. Reasoning is that
the low fills over time and bands will become less organized as
dynamics weaken. In addition, the daytime hours will feature
temperatures above freezing, limiting accumulation potential.

As this low exits to the east, s/wv ridging will develop by
Tuesday and Wednesday, ahead of a potent cold front due Thursday.

This next system will be quite strong, but will take a dry path
along our northeastern border and into the Four Corners. Despite
this, the height falls and cold front will be enough for at least
some flurries, as well as strong winds and a sharp temperature
drop. Dry and cold north/northwest flow develops by friday and
into the holiday weekend.


.AVIATION...For the 18Z package...A weather system will cause
scattered-numerous rain and snow showers from KPAN-KSJN southward
with areas of MVFR conditions likely. Elsewhere, expect only
isolated activity and VFR conditions. Showers are forecast to
decrease after 06Z Monday, with a chance continuing in the White
Mountains through Monday. Aviation discussion not updated for TAF


.FIRE WEATHER...For today, a passing low will bring rain and
snow showers, primarily along the eastern Mogollon Rim and White
Mountains. Most locations are expected to receive 0.20 inches of
liquid precipitation or less. On Monday, dry weather returns,
although a slight chance for showers remains in the vicinity of the
White Mountains.

Tuesday through Thursday...On Tuesday, expect dry weather, near to
above normal temperatures and light winds. Southwest winds increase
on Wednesday before a cold front delivers chances for showers and
much cooler temperatures on Thursday.






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