Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 051610

Area Forecast Discussion
National Weather Service Tucson AZ
910 AM MST Mon Dec 5 2016

.SYNOPSIS...A weather system moving northeast of the area may bring
a few rain and snow showers to the White Mountains Tuesday night
into Wednesday. Otherwise dry conditions will prevail into next
weekend. Above normal temperatures will occur except for Wednesday
and Thursday.


.DISCUSSION...IR/visible satellite imagery and surface observations
indicate scattered to broken thin cirriform clouds across southeast
Arizona at this time. Dewpoints at lower elevations valid 15Z ranged
from the upper teens-mid 20s, and these temps were generally 2-8
degs lower versus 24 hours ago. Surface temps valid 15Z were nearly
2-6 degs warmer versus this time Sunday, except across the far
southeast where temps were about 5 degs cooler versus 24 hours ago.

05/12Z KTWC sounding total precip water value was 0.33 inch, and the
profile exhibited increased moisture in the 600-200 mb layer versus
Sunday morning. 05/12Z upper air plots depicted a broad trough over
Canada extending southward into the northern CONUS. Meanwhile, a
large area of high pressure was well west of the southern
California/northern Baja California coasts. These systems have
resulted in a light to moderate northwesterly flow aloft regime
across southeast Arizona.

The upper trough will continue to deepen into Tuesday. Thus, dry
conditions will continue although variable amounts of mainly
cirriform clouds will move across the area. A shortwave trough will
move southeastward across the Four Corners region Tuesday night,
then continue eastward into the central CONUS plains Wednesday.

There continue to be differences amongst the NAM/GFS/ECMWF regarding
precip potential for Tue night/Wed. The 05/12Z NAM continues similar
versus previous NAM solutions, and depicts a few hundredths of an
inch of liquid amounts mostly across western Pima County as early as
Tue morning and continuing into Wednesday. Meanwhile, the 05/12Z GFS
continues to depict a few hundredths of an inch across the White
Mountains Wednesday.

However, this GFS solution now depicts measurable amounts much
further south, or generally south-to-southeast of Tucson. The 05/00Z
still seems to be the most reasonable solution with regard to
depicting measurable amounts Wednesday from the White Mountains
northward to the Four Corners region. At any rate, will await
receipt of the 05/12Z ECMWF before making any changes to the
official forecast that depicts a slight chance of rain/snow showers
mainly across the White Mountains Tue night-Wed. Thereafter, dry
conditions are forecast to occur area-wide Wednesday night into next
weekend under wly/nwly flow aloft.

High temps today will generally be about 2-5 degs warmer versus
Sunday followed by no significant change in high temps Tuesday.
Cooler temps will occur Wednesday as the shortwave trough passes
northeast of the area. A warming trend will then prevail Thur-Fri,
then only very minor daytime temp changes next weekend. High temps
Fri-Sun will average about 2-5 degs or so above normal depending
upon location.


.AVIATION...Valid through 06/18Z.
Expect SCT-BKN clouds above 20k ft AGL and surface wind variable in
direction at less than 12 kts into Tuesday morning. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...There is a slight chance of rain and snow showers
across the White Mountains Tuesday night and Wednesday. Otherwise,
dry conditions will continue into the upcoming weekend. 20-ft winds
will be gusty around 15 to 20 mph from the southwest on Tuesday,
with winds becoming easterly on Thursday and Friday. 20-foot winds
will mainly follow terrain at less than 15 mph at other times.





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