Weather Service Report


461 
FXUS65 KTWC 272154
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
254 PM MST Mon Feb 27 2017

.SYNOPSIS...A Pacific weather system will bring a few showers 
west of Tucson this afternoon, then an increasing chance of 
valley rain and mountain snow showers this evening into Tuesday.
Strong gusty winds will also develop today and Tuesday. Dry 
conditions with a strong warming trend will return Wednesday into 
next weekend.

&&

.DISCUSSION...Our main weather story will be a trough of low
pressure currently consolidating immediately upstream through 
Pacific states. The remains of the low previously off the
California coast has been co-opted into the base of the trough and
is currently shearing through Yuma county with showers increasing
from the southwest there. This area will spread east and north
over the next 12 hours, and will be more of an impact for areas
north of Tucson tonight. Most shower activity south of Casa Grande
will be light to moderate this evening.

The front associated with the main part of the system will push 
through from the west Tuesday, with shower activity increasing in 
our area ahead of the front in the morning hours, before 
diminishing behind the front Tuesday afternoon. Storm total valley
rainfall between .1 and .5 inches, with lighter amounts near 
international border areas. Snow levels around 7k feet tonight, 
then between 6k and 7k feet Tuesday. 5 to 10 inches above 6500 
feet around the Mt Lemmon and Mt Graham areas, with 10 to 16 
inches in the mountains of northern Graham and Greenlee counties 
(southern portions of the White Mountains).

Clearing from the west late Tuesday. At that point we shift into a
pattern with much less potential for lower latitude energy. 
Instead of trough/ridge/trough/ridge, we'll be 
ridge/flat/ridge/flat with dry conditions and above average 
temperatures from Thursday through at least the first half of 
next week.

&&

.AVIATION...Valid through 28/23Z.
Isolated -SHRA west of KTUS into the early evening hours with 
increasing valley -SHRA and mountain SHSN late tonight and Tuesday. 
The heaviest precipitation should occur north of KTUS. Cloud decks 
AOA 15k ft AGL will lower to 5k-8k ft AGL by 28/08Z. Expect possible 
MVFR conditions overnight tonight and especially on Tuesday. Surface 
wind sly/swly at 12-20 kts with gusts up to 28 kts thru 28/14Z. The 
strongest speeds will be east of KTUS in the vicinity of KDUG, KALK 
and KSAD. Surface wind will increase after 28/14Z, with swly/wly 
surface wind at 16-26 kts and gusts to 35-40 kts, with the strongest 
speeds in the vicinity of KDUG, KALK and KSAD. Aviation discussion 
not updated for TAF amendments.

&&

.FIRE WEATHER...A fast moving Pacific weather system will bring a 
slight chance of showers west of Tucson through this evening. There 
is a better chance of valley rain and mountain snow showers late 
tonight and Tuesday. The least favored area for significant 
precipitation is southeast of Tucson. Dry conditions will prevail 
Tuesday night into early next week. Expect gusty south to southwest 
20-foot winds through early Tuesday morning and strong and gusty 
southwest to west winds from late Tuesday morning through the early 
evening hours Tuesday. Thereafter, a generally light easterly wind 
regime will prevail Wednesday through Friday followed by normal 
diurnal wind trends next weekend.

At this time, critical fire weather thresholds are not expected to 
be met on Tuesday. Although wind speeds will easily meet criteria, 
increasing moisture will result in minimum relative humidity values 
of only 20-25 percent over portions of Cochise and Graham counties 
and higher values elsewhere.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from 6 PM this evening to 5 PM MST Tuesday 
for AZZ510.

Blowing Dust Advisory until 5 PM MST this afternoon for AZZ508.

Winter Weather Advisory from 6 PM this evening to 5 PM MST 
Tuesday for AZZ511-514.

&&

$$

Meyer/Zell

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