Area Forecast Discussion
Issued by NWS Tucson, AZ

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000
FXUS65 KTWC 231525
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
825 AM MST Tue May 23 2017

.SYNOPSIS...Strong high pressure aloft will bring well above
average daytime temperatures through midweek. Thursday and Friday
will see us between low pressure developing north of the area and
high pressure shifting southward. As a result, expect gusty winds
and several degrees of cooling. Strengthening high pressure next
weekend will once again push temperatures above average.

&&

.DISCUSSION...
Mid morning water vapor imagery continues to reveal strengthening
high pressure over the southwestern CONUS with weak low pressure and
moisture well west of Baja California. Despite the moisture evident
on water vapor imagery, skies remained clear across the area.
Morning temperatures bottomed out in the upper 60s and had no
problem rebounding into the lower 80s as of 15z.

Incoming 12Z guidance, along with observational trends, reveal the
inherited forecast is in great shape. Aside from minor adjustments
to winds based on latest few runs of the HRRR, no updates appear
necessary. Highs still look on track to flirt with 100 yet again
this afternoon in/around Tucson. Even warmer temperatures are
forecast on Wednesday with low 100s a virtual certainty across the
deserts.

&&

.AVIATION...Valid thru 24/18Z.
High pressure will mean mostly clear with occasional patches of
thin cirrus. Normal diurnal wind trends, gusty at times in the
afternoon. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions will prevail into next weekend.
Expect afternoon 20-foot wind gusts through Wednesday to around 20
mph. Stronger winds are forecast to occur Thursday and Friday we
are caught between low pressure north of the area and high
pressure through central and northern Mexico. The combination of
strong and gusty southwest to west winds, low relative humidity
and a high to very high fire danger may create critical fire
conditions Thursday and Friday, especially across higher terrain
east to south of Tucson. With this in mind, a Fire Weather Watch
has been issued for portions of fire weather zones 151, 152 and
153 Thursday and Friday. Less wind will then mitigate critical
fire conditions over the weekend into early next week.

&&

.PREV DISCUSSION...Wow, that`s an impressive late season trough
consolidating downstream through the Midwest and Southeast over the
48 hours. The pattern is kind of stacking up and that will put the
squeeze on Southeast Arizona. With the mean ridge position upstream
over the eastern Pacific dirtying up, we will be caught between a
new ridge orientation through central and northern Mexico to our
south, and a system digging out of British Columbia into northern
and central portions of the Intermountain West. That means gusty
winds Thursday and Friday with possible fire weather and blowing
dust concerns.

After our current stretch of heat through Wednesday or Thursday, we
can also expect several degrees of cooling back to near seasonal
normals for late May to end the week.

We will then see a regional ridge take control late in the weekend
into early next week, but it`s a complicated and dirty one with
several weaknesses in the flow. We`ll also have to watch out for any
pre-season weak mid to level moisture fluxes from the south.
Temperatures pushing back to several degrees above average is a good
guess, but we may not be totally dry. A dry high-based thunderstorm
or two is not out of the question east of Tucson next week. It
happens.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Thursday morning through Thursday
evening for AZZ151>153.

Fire Weather Watch from Friday morning through Friday evening
for AZZ151-152.

&&

$$

Leins/Meyer

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