Heat in Arizona, June 22 to 23, 2018

Area Forecast Discussion
National Weather Service Tucson AZ
927 AM MST Fri Jun 22 2018

.SYNOPSIS...Dry and clear conditions continue this week. High
temperatures today will approach the hottest of the year so far,
moderating on Saturday into next week. Some moisture will move into
the area over the weekend, but no precipitation is expected. We
may see enough moisture for a few storms later next week.

&&

.DISCUSSION...Our pattern continues with the westerlies a little
too deep for more monsoon activity. High pressure strengthening
overhead today with an excessive heat warning for many of our mid
to lower valley locations and lower deserts. Troughiness through
the front range of the Rockies will help cool things down to
average values for late June over the weekend.

Keeping an eye on the easterly wave activity across central
Mexico. They're coming across and exiting into the eastern Pacific
just south of the Gulf of CA. As the westerlies weaken and lift a
little further northward next week, it should allow that activity
to track further north as well. A few storms not out of the
question later next week, but ultimately most mid range model
resolutions and ensembles argue we aren't done with pesky westerly
flows cutting that off again.

&&

.AVIATION...Valid through 23/18Z.
Clear skies. SFC wind will generally be less than 12 kts, with
some afternoon/early evening gustiness. The exception will be in
the upper Gila River valley near KSAD where a NWLY SFC wind of
12-18 kts will prevail from the mid afternoon thru early evening
hours. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Mostly dry conditions persist through the
forecast period, although surface moisture does temporarily
increase over the weekend. We also may see a modest moisture
increase bring in a few thunderstorms later next week. The
hottest temperatures arrive today, peaking around 105- 110 degrees
in the lower elevations of Pinal, Pima and Graham counties.
20-foot winds will generally be 15 mph or less for most of the
forecast period, except in the Upper Gila River Valley where winds
of 15-20 mph are expected at times during the afternoon and early
evening hours. Breezy conditions then expand in coverage Saturday
and Sunday with a broader area of 12-20 mph, and the strongest
winds stretch across portions of Cochise and Graham counties.

&&

.PREV DISCUSSION...A ridge of high pressure aloft will strengthen
a bit more today resulting in the hottest readings so far this
year. That said, an Excessive Heat Warning has been posted for the
lower deserts of southeast Arizona today. Temperatures will start
lowering a few degrees this weekend into Monday before high
pressure becomes reestablished over east- central Arizona Tuesday
and Wednesday. This change in the pattern will result in another
warmup, with high temperatures peaking around Tuesday or
Wednesday. Thereafter, models showed a trough of low pressure
moving inland off the Pacific with the tail end passing through
Arizona. This feature will bring some cooler air into the area
with high temperatures lowering a few degrees late next week.
Otherwise, expect dry conditions with some afternoon breeziness
from time-to-time.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST this evening for AZZ501-
502-504-505-509.

&&

Meyer

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