Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 210445

Area Forecast Discussion
National Weather Service Tucson AZ
945 PM MST Sat Jan 20 2018

.SYNOPSIS...The cold front that brought valley rain, mountain
snow and gusty winds to the area today has moved into western New
Mexico. Cloud will be decreasing overnight as the upper low moves
across northeast Arizona. Much cooler temperatures moving into the
area will result in a freeze in the lower deserts, including
Tucson, tonight and again Sunday night. Southern and eastern
valleys will be much colder. Dry conditions with warmer
temperatures next week.


.DISCUSSION...Still a few light showers/sprinkles across the
eastern half of the forecast area associated with the cold front
near the New Mexico border as it continues east and trailing
upper level trof. Rainfall amounts were rather light, mostly less
than 0.10", with a few localized higher amounts near 0.20". No
snow reports in the mountains but believe amounts were less than
2". As cloud cover diminishes later tonight into Sunday morning,
could see patchy areas of fog, mainly north and east of Tucson.
With a colder air mass moving in, can`t rule out some areas of
frost also, especially across Cochise county. Main question
tonight will be how cold will it get across the lower deserts
where a freeze warning is in effect Sunday morning. Dewpoints from
Tucson east, as of 9 pm, where in the 30s to lower 40s from Tucson
east while they were in the 20s out in the western deserts. 21/00z
MOS guidance not as cold with overnight lows previous guidance.
However will let the freeze warning going tonight. Sent out an
update for the forecast earlier this evening based on trends.

Cold airmass in place will lead to well below normal high
temperatures on Sunday and cold overnight lows into Monday morning
versus Sunday morning.

The current forecast high for Tucson on Sunday is 56 degrees
which is 10 degrees BELOW normal. If this occurs it would mark the
first double digit below normal high temperature since late July
last year. 00z MOS guidance has come in cooler for Sunday.


.AVIATION...Valid thru 22/00Z.
Decreasing clouds from west to east thru 22/12z then mostly clear
conds. Elevated wly winds will continue this evening, briefly
tapering off early Sunday morning before increasing again to 10-20
kts with a few spots up to around 25 kts near KSAD. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Precipitation will end east of Tucson by Sunday
morning, then dry conditions will prevail Sunday afternoon into
next Friday. Gusty northwest winds will favor the Upper Gila
River Valley including Safford on Sunday. Otherwise, 20-foot winds
will be terrain driven mainly less than 15 mph at other times
through Wednesday. Breezy west winds may return late next week.


 Freeze Warning from 1 AM to 9 AM MST Sunday for AZZ502-504-505.

 Freeze Warning from 1 AM to 9 AM MST Monday for AZZ502-504-505.



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