Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 201026

Area Forecast Discussion
National Weather Service Tucson AZ
326 AM MST Sat May 20 2018

.SYNOPSIS...After a mild weekend, winds increase on Monday and
Tuesday with a slight chance of thunderstorms developing over the
White Mountains. Otherwise, conditions remain dry as the heat
begins to ramp up late next week.


.DISCUSSION...The weekend comes to a close with yet another day of
dry and benign southwesterly upper-level flow across the region.
Temperatures warm slightly from yesterday, reaching just a few
degrees above normal for this time of year.

However, the pattern begins to shift on Monday as a deepening low
digs south down the state of California, squeezing the gradient over
our area producing strong afternoon breezes. This could kick up
patchy dust across the lower deserts of Pima/Pinal Counties and
localized fire weather concerns are possible. Moisture also begins
to creep across the New Mexico/Arizona border, stretching into the
White Mountains. With daytime heating, this may allow for weak mid-
level instability and resultant high-based thunderstorm development.
Chances remain slight for actual precipitation at the surface, and
any isolated activity will quickly be carried outside our forecast
area on 30 kt southwesterly cloud-layer mean winds.

Breezy conditions continue on Tuesday, but at slightly reduced
strength. Temperatures also drop several degrees back near seasonal
averages as the upper low makes its closest approach before lifting
out to the northeast. Winds decrease further on Wednesday as the
pattern transitions into a building ridge, which turns up the heat.
Many valley locations approach or exceed triple digit temperatures
beginning Friday into the weekend.


.AVIATION...Valid through 21/12Z
SKC through the period. Surface wind will be light early this
morning, then becoming SWLY/WLY at 8-12 kts during the afternoon and
evening hours. Aviation discussion not updated for amended TAFs.


.FIRE WEATHER...A weather system passing north of the area will
bring an increase in wind speeds both Monday and Tuesday. This in
combination with low humidities will create isolated areas of brief
critical fire weather conditions, though it is not expected to be
widespread or long-lived enough to warrant a Red Flag Warning. The
system will also bring a slight chance of thunderstorms to the White
Mountains Monday afternoon. Temperatures will remain slightly above
normal with little day to day variation in highs before a warming
trend occurs the second half of the week into the weekend. Beyond
Tuesday, lighter winds with occasional afternoon gusts will prevail.





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