Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 080943

Area Forecast Discussion
National Weather Service Tucson AZ
242 AM MST Fri Dec 8 2017

.SYNOPSIS...After a cold start to the morning, sunny skies and
below normal daytime temperatures are expected today. High pressure
aloft will then build across the area this weekend into next week,
resulting in dry conditions and a return to above normal
daytime temperatures.


.DISCUSSION...Clear skies and cold temperatures were noted across
southeast Arizona early this morning. 09Z temperatures ranged from
the 20s in the valleys of Santa Cruz and Cochise counties, to the
upper 30s to lower 40s in eastern Pima county across the Tucson
metro area. Therefore, Freeze Warning was already verifying across
eastern portions of the forecast area. With several more hours of
radiational cooling, expect temperatures to bottom out around the
freezing mark in central Tucson and in the upper 20s to around 30
degrees in the outlying portions of the metro area. The Freeze
Warning remains in effect through 9 am this morning. Otherwise,
sunny skies and below normal daytime temperatures are expected
today as readings this afternoon top out 4-7 degrees below normal.

High pressure aloft will then strengthen across the western United
States this weekend, persisting through the end of next week. The
highly amplified ridge pattern will stretch all the way from the
desert southwest into the Pacific northwest, keeping the storm track
well north and east of our area. Expect dry conditions and daytime
temperatures 4-8 degrees above normal through this period.

There will be some high clouds from time to time, especially late
Friday night into early Monday when a weak upper low develops west
of the Baja spur and moves east across Sonora, Mexico. Flow around
the low does pull some moisture northward through Sinaloa and
southern Sonora as it moves east across northern Mexico. However,
the strength of the high pressure ridge keeps the low suppressed to
far south of our area to generate much more than mid/high level


.AVIATION...Valid thru 09/12Z.
Clear skies with SFC wind generally less than 12 kts thru the
forecast period . Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions for the next 7 days. 20-foot winds
will generally be easterly through next Wednesday. Elevated easterly
winds are expected on Saturday and Sunday at 15-20 mph, otherwise
wind speeds will generally be less than 15 mph. Daytime temperatures
will be 4 to 7 degrees below normal today, warming to 4 to 8 degrees
above normal this weekend into next week.


.CLIMATE...Tucson airport will set the record for the latest
occurrence of 1st 40 degree low temperature of the cool season. The
previous latest 40 degree low was December 5, 2013.


 Freeze Warning until 9 AM MST this morning for AZZ503-504-506>509.




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