Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 041530

Area Forecast Discussion
National Weather Service Tucson AZ
830 AM MST Sun Dec 4 2016

.SYNOPSIS...Dry conditions will occur through Tuesday. A weak system
moving north of the area may then bring a few snow showers to the
White Mountains Tuesday night and Wednesday. Dry conditions with
above normal daytime temperatures will then prevail during the
latter part of the week and next weekend.


.DISCUSSION...Clear skies prevail across southeast Arizona at this
time along with light winds. 04/12Z KTWC sounding depicted a very
dry profile, with total precip water value of 0.27 inch. 04/12Z
upper air plots depicted a 556 dm low centered over far southern
Sonora Mexico, a sprawling high pressure centered well west of the
southern California coast near 28N/135W, and a broad trough over
western/central Canada. Moderate to fast nely/nly flow above 700 mb
was observed across southeast Arizona.

The southern Sonora upper low which brought some light rain/snow to
locales east-to-south of Tucson mainly Saturday night will weaken
while moving northeastward toward the Texas Big Bend Monday morning.
Meanwhile, a ridge axis aloft extending from the large area of high
pressure west of southern California will extend eastward across the
area today. This feature will result in clear skies at least into
this evening. Some increase in cirriform clouds perhaps as early as
late tonight though more likely Monday will occur ahead of a
deepening upper trough over the Pacific Northwest/northern Rockies.

Clouds should continue to increase sufficiently for partly cloudy
skies Monday night and Tuesday as a broad upper trough develops
across the western/central CONUS. The inherited official forecast
continues with dry conditions into Tuesday, and this seems
reasonable based on the 04/12Z NAM, 04/06Z GFS and 04/00Z ECMWF.

A speed max aloft is progged to move southeastward across the Four
Corners region/central Rockies Tuesday night/Wednesday. This system
will likely provide enough vertical ascent for a few snow showers
mostly across the White Mountains. Have noted that the 04/12Z is
further west with the potential for measurable precip, but for now
this solution is discounted. The deterministic ECMWF is preferred
versus the wetter NAM and considerably drier GFS. Dry conditions
will then return area-wide Wednesday night and continue into next
Saturday under wly/nwly flow aloft.

Expect a few degs of daily warming into Monday followed by cooler
temps by Wednesday. A warming trend will then prevail Thur-Fri then
no significant change in high temps next Saturday. High temps Fri-
Saturday will average about 2-5 degs or so above normal depending
upon location.


.AVIATION...Valid through 05/18Z.
Expect VFR conditions with clear skies into this evening, then a FEW
to perhaps BKN clouds above 20k ft AGL late tonight into Monday
morning. Surface wind variable in direction at less than 12 kts
through the period. Aviation discussion not updated for TAF


.FIRE WEATHER...There is a slight chance of snow showers across the
White Mountains Tuesday night and Wednesday. Otherwise, dry
conditions will prevail into next weekend. Some gusty southwest
winds will occur Tuesday, and gusty east winds should prevail
Thursday and Friday. 20-foot winds will mainly be less than 15 mph
at other times.





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