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 FXUS65 KFGZ 170419

Area Forecast Discussion
National Weather Service Flagstaff AZ
919 PM MST Sat Dec 16 2017

.SYNOPSIS...A low pressure system moving across far southern
Arizona on Sunday and Monday will bring cooler temperatures,
along with chances for rain and snow showers primarily along the
eastern Mogollon Rim and White Mountains. Dry weather and a
warming trend are forecast from Monday through Wednesday. By
Thursday, another low pressure system may impact the area.


.UPDATE...The center of a deepening low pressure area is moving
across Northern Baja with a rather impressive lightning show this
evening. This low will continue to move across the Baja then move
slightly northeast and across southern Arizona Sunday and Monday.
High clouds will bring mostly cloudy conditions to much of
northern Arizona tonight which will moderate the low temps in some
of the lower elevations. Have adjusted some temps and cloud cover
upwards for tonight.


.PREV DISCUSSION /329 PM MST/... Model solutions continue to shift
concerning timing and location of the upper level trough as it
transitions inland from the Pacific. Current solutions have the
trough deepening into a closed low well over the Baja Penisula.
This is further south than previous tracks, and compared to
previous model solutions limits the northern spread of moisture
over the Mogollon Rim.

The timing of the system has also slowed down as the low becomes
closed off a little later in its track, limiting how much moisture
will fall over the Coconino and Yavapai counties, and focusing the
moisture plume closer to the Arizona - New Mexico state line.

As the low tracks further south over Sonora and into Southern
Arizona this will also allow temperatures to warm slightly more
during the day Sunday. This increasing snow level will also limit
some snowfall amounts as a rain snow mix becomes more likely.

Unfortunately these changes have combined to severely limit
snowfall amount across much of the area with Flagstaff and the
Western Mogollon Rim now looking at limited snow if any, and much
of the Eastern Mogollon Rim struggling to get 1 to 2 inches. The
White Mountain will still see the higher amounts from this storm,
but the higher elevations are expected to max out around 5 inches
of snowfall.

As the system exits the area on Monday zonal flow looks to become
established before the next system impacts the area Thursday.
Winds will increase on Wednesday ahead of the next trough, with
the details concerning this next event still highly uncertain due
to its distance in the long term. Interested parties should stay
current with the latest forecasts since this system has the
potential to impact travel and other outdoor activities through
the rest of next week.


.AVIATION...For the 06Z package...Expect predominately VFR
conditions and light winds over the next 24 hours. A weather system
will bring an increasing chance of rain and snow showers to Northern
Arizona during the day Sunday, scattered to numerous from KPAN-KSOW
southward with areas of MVFR conditions. Elsewhere, only isolated
activity. Snow level 5-7 kft MSL. Aviation discussion not updated
for TAF amendments.


.FIRE WEATHER...The cold front moving through Sunday will bring
light rain and snow showers to the area, mostly south of the
Mogollon Rim and over the White Mountains. Expect less than 0.20 in.
precipitation maximum. Temperatures will near normal through Monday
with skies clearing Sunday evening.

Tuesday through Thursday...Mostly sunny and warmer with temperatures
5-10 degrees above normal Tuesday and Wednesday, but dropping back
to normal Thursday with the next trough passing to the north.
Minimum RH values will be in the 20s. Winds will be light through
the period except Wednesday with south-southwest winds at 15 gusting
25 mph in the afternoon.





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