Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 181700
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
1000 AM MST Sat Mar 18 2017

.SYNOPSIS...The unseasonable warmth of late will continue into
the early part of the new week with little change. A storm system
is expected to move across the region the middle part of next week
which will result in cooler temperatures, gusty winds and a
chance of showers.

&&

.DISCUSSION...Clear skies or just of few thin cirriform clouds
across southeast Arizona this morning along with light easterly to
southerly surface winds. 17/12Z KTWC sounding total precip water
value of 0.44 inch was nearly identical to 24 hours ago. Surface
temps at lower elevations valid 9 AM MST were mostly 2-4 degrees
warmer versus 24 hours ago. The exception was Safford/KSAD where
the temperature was 8 degrees warmer versus this time Friday.

Upper level ridge axis extended from southern New Mexico northward
into Montana, and an upper trough was approaching the West Coast of
the CONUS. Expect sunny skies or mostly sunny skies today, with just
some thin cirriform clouds at times, or a few cumuloform clouds near
mountains. High temps this afternoon are forecast to be a couple of
degrees or so warmer versus Friday, and will approach or perhaps
record values for at least some locales. A few wind gusts will also
occur today due to daytime heating.

There are no updates necessary at this time. Please refer to the
additional sections for further detail.

&&

.AVIATION...Valid through 19/18Z.
Mostly clear skies with patches of cirrus clouds at times and a few
cumulus clouds around 10-12k ft over the southern mountains this
afternoon. Winds will continue to be light with a few  afternoon
gusts to 20 kts and somewhat variable in direction. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Very warm and dry conditions will continue into
early next week with continued low RH levels in the afternoon and
marginal overnight recoveries. Winds Saturday and Sunday afternoons
will be more westerly but remaining below 15 mph with a few higher
gusts. One or two dry lightning strikes are not out of the question
in the Chiricahua Mtns of far southeast Cochise county Sunday
afternoon with a modest mid level moisture increase from Mexico.

A Pacific storm system is expected to move across the area the
middle part of next week with gusty SW winds Monday through
Thursday. Any more widespread moisture is not expected to ramp up
until at least late Wednesday so dry and breezy conditions expected
for a few afternoons. Borderline critical conditions possible
Tuesday and Wednesday mainly zone 152 then there is a fair chance of
showers Wednesday night into Thursday. There is a decent chance for
another storm system late the following weekend.

&&

.CLIMATE...The average monthly temperature for Tucson International
Airport (TIA) through March 17 ranks as the warmest-to-date (and at
this time it looks like a sure thing to end the month still in the
lead). We`ve had a total of 6 days of 90 degrees or warmer so far,
with 5 consecutive days through Friday. This ties for the longest
stretch of 90s in March. That record should be broken today and then
added to through Monday or Tuesday. We should also exceed the all-
time March record for the number of 90+ days (currently 8 set in
1910).

&&

.PREV DISCUSSION /304 AM MST/...The ridge! The ridge! (in Herve
Villechaize`s voice) Temps will continue to run 15 to 20 degrees
above average into early next week, maxing out today and Sunday. A
few daily and monthly records are threatened, with some details
below in the Climate section.

We`ve been watching a bit of mid level moisture working all the way
up from central Mexico into Chihuahua all week, with progress slowed
by the orientation of the ridge over the past 24 hours. HRRR has the
ridge idea for this afternoon, pushing unorganized convection into
northern Chihuahua and far eastern Sonora. We have isolated
thunderstorm coverage for the Chiricahua mountains of far southeast
Cochise county tomorrow afternoon before that is pushed off to the
east in an increasing southwesterly flow ahead of the storm system
approaching from the west.

The aforementioned Pacific storm system, which we have also been
watching all week, will bring increasing surface winds by Tuesday
afternoon, with windy conditions for the area Wednesday ahead of a
surface frontal boundary. As is often the case with transition
season systems, we will probably be a little on the moisture starved
side this far south. A few showers around the area late Wednesday
afternoon and Wednesday night / Thursday morning, but most of the
action will be to our north. Temperatures will drop back to near or
a little below seasonal normals behind the front (which should be
east of our area by Thursday morning).

Another mainly windy system pushes through the area next weekend, so
temperatures shouldn`t have enough time to bounce back to extreme
levels.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

Francis/Meyer

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