Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 152016

Area Forecast Discussion
National Weather Service Tucson AZ
116 PM MST Fri Dec 15 2017

.SYNOPSIS...Sunny and dry conditions will prevail across southeast
Arizona through Saturday. A quick moving weather system will bring
colder temperatures, valley rain and mountain snow showers Saturday
night and Sunday. Slightly warmer temperatures and dry weather will
return early next week before another system moves into our area
late in the week.


.DISCUSSION...An easterly surface gradient will bring gusty winds
at times today, importing a few degrees of cooling in the process.

We`re still on track for the pattern to buckle into a mean trough
position over western states over the weekend, with a winter
storm bringing a good chance of valley rain and mountain snow
Sunday. Initial thicknesses suggest snow levels starting around
7500 ft Saturday evening, dropping to 6k ft Sunday morning. We`ll
see our daytime high in the late morning to mid day hours before
the front moves through, with snow levels dropping back to 5k feet
by late afternoon or early evening. As the main moisture is pushed
eastward, we may see snow levels as low as 4500 ft Sunday evening.
It`s a fairly fast system with unfavorable antecedent conditions,
so not much time to really get a strong moisture tap. 24 hour QPF
values in the .1 to .2 inch range in the valleys Sunday, with .3
to .5 in the mountains. A few locations above 8k feet may get up
to 6 or 7 inches, with 3 to 5 inches between 6k and 8k feet,
maybe 1 inch at 5k feet. Low end Snow Advisory may be needed
Sunday. Cooler temperatures, several degrees below average.

A shortwave ridge to zonal flow the first half of the week will
bring dry conditions and a temperatures creeping back up to near
or a little above average. Another system may impact the area late
in the week into the holiday weekend. Early signs showing it to be
a little stronger and colder than our Sunday storm.


.AVIATION...Valid thru 17/00Z.
Clear with increasing clouds from west to east late in the
period. Sfc wind ely at 8-15 kts with gusts to 25 kts at times,
through this afternoon. Wind speeds diminish overnight into
Saturday morning. Aviation discussion not updated for TAF


.FIRE WEATHER...Easterly 20 foot winds with speeds of 10 to 15
mph and gusts to 25 mph at times. Otherwise, mild and dry weather
will prevail Friday and Saturday. A stronger weather system will
bring cooler temperatures, valley rain and mountain snow to the
area Sunday. Drier air and warmer temperatures will then return
next week.






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