Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 230301

Area Forecast Discussion
National Weather Service Tucson AZ
800 PM MST Wed Mar 22 2017

.SYNOPSIS...A storm system will bring a chance of showers and
thunderstorms tonight into Thursday. This system will result in much
cooler temperatures Thursday, as well as gusty west to northwest
winds. Dry conditions with somewhat milder temperatures and gusty
winds at times will occur over the weekend into early next week.


.DISCUSSION...In the big picture, an upper ridge was situated over
central/eastern Texas, with a trough and associated storm system
over California. Although the ridge was well east of the area and
most locations across southeast Arizona reported cooler highs today
(generally 1-4 degs of cooling), clear skies and southwest flow
ahead of the approaching system allowed areas east of Tucson to warm
to just about yesterday`s levels, with a record high broken at the
Bisbee-Douglas Airport (high today was 87 degrees which broke the
old record of 86 degrees set in 1997). The breezy southwest winds
this afternoon have diminished considerably this evening. However,
still expect elevated south to southwest winds tonight (10-15 mph)
with the system approaching from the west.

Impressive height falls are associated with the California storm
system. IR and water vapor satellite imagery indicate the moisture
band ahead of the system (which produced showers and thunderstorms
across western Arizona this afternoon/early evening) has lost it`s
Pacific feed. However, even with limited moisture, in conjunction
with height falls may still see a few showers or thunderstorms this
evening, primarily west of Tucson as the system moves east. Best
chances for precipitation across southern Arizona will be overnight
through mid-day Thursday as a vort max west of San Diego rotates
through base of the trough and across the area. Overall, forecast
package looks to be in good shape with precipitation timing and
highest precipitation chances to the north/northeast of the Tucson
metro area. No updates.


.AVIATION...Valid through 24/00Z.
Cloud decks will lower from west to east late tonight and Thursday,
as isolated to scattered -TSRA/-SHRA move in from the west,
impacting KTUS and KOLS after 23/09z. Prevalent conditions should
remain VFR.

Surface wind will continue to diminish this evening, with SLY/SWLY
surface wind at 10-15 kts thru 23/16Z. Increasing surface wind aft
23/16Z, with WLY/NWLY surface wind at 17-25 kts and gusts to 25-33
kts Thursday afternoon. The strongest wind Thursday afternoon will
be east of KTUS, in the vicinity of KALK, KDUG and especially KSAD.
Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...A Pacific storm system will bring a chance of
showers and thunderstorms tonight and Thursday, with the main focus
north/northeast of Tucson. A few snow showers may occur across the
White Mountains northeast of Safford Thursday night. Dry conditions
will then prevail Friday into Sunday. There is a slight chance of
showers across the White Mountains next Monday.

There will be gusty west to northwest winds Thursday accompanied by
higher RH values, then less wind Friday into Saturday. Some gusty
afternoon west winds are forecast to return Sunday and next Monday.


.PREV DISCUSSION...The large ridge axis is now east of our area,
with an increasing southwesterly flow ahead of the deep trough now
onshore near the west coast. Clouds increasing from the west
through tonight. Based on the track of the low a little north of
our area, and the associated cold front now entering western
Arizona, it looks like the best chances for precip for most of our
area will be directly associated with the frontal passage
tomorrow morning. Some instability and residual moisture behind
the front tomorrow afternoon for a few showers or thunderstorms
mainly northeast of Tucson. Rainfall between a trace and .1 in
valleys with a dusting to an inch or two of snow possible above
7000 feet. Most of the significant precip should be north of our

Winds are holding nicely below advisory levels. The cooler air is
still on track behind the front tomorrow.

A shortwave ridge to end the week with temperatures jumping back
above average, but well short of what we`ve been seeing. The next
system this weekend will be a more traditional transition season
system, with wind the main concern and enough cool air to push
temperatures back down a few degrees.





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