Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 221707
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
1005 AM MST Thur Jun 22 2017

.SYNOPSIS...Expect very hot and near record temperatures into this
weekend. Dry conditions will prevail for much of the area into
Saturday. A more favorable pattern will then provide scattered
afternoon and evening thunderstorms especially Sunday and continuing
into the middle of next week.

&&

.DISCUSSION...Very hot temperatures to continue today, although not
quite as hot as temperatures that were recorded earlier this week.
Several HRRR solutions as well as the Univ of AZ WRF-NAM suggest
that a few thunderstorms may occur briefly this afternoon across the
White Mountains and near the International border adjacent Santa
Cruz/Cochise Counties. However, am opting to maintain a dry forecast
area-wide at this time.

Have also noted that the 22/12Z MAV/MET guidance wind speeds have
trended downward for KSAD versus the past several solutions. Thus,
am still leaning toward a scenario of wind speeds in the Upper Gila
River Valley (including Safford), as well as in the northern portion
of Fire Zone 152, will only be marginally sufficient to briefly
achieve Wind Advisory or Red Flag Warning criteria.

The current forecast is in excellent shape and no updates are
warranted at this time. Please refer to the additional sections for
further detail.

&&

.AVIATION...Valid thru 23/18Z.
Expect clear skies to scattered clouds at 10k-15k ft AGL into Friday
morning. Surface wind this afternoon nwly 10-25 kts with gusts to
near 35 kts. The strongest speeds will be northeast of KTUS and
especially near KSAD. Surface wind variable in direction less than
12 kts at other times. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Dry conditions will prevail today and Friday and
across much of the area Saturday. The exception is near the New
Mexico border where a slight chance of thunderstorms may occur
Saturday afternoon. A more favorable pattern for thunderstorms will
then prevail Sunday through next Wednesday. Expect scattered
afternoon and evening thunderstorms, especially east to south of
Tucson. However, the coverage of thunderstorms Monday into Tuesday
may expand further west to also include Fire Zone 150 west of Tucson.

Otherwise, 20-foot winds will generally be terrain driven less than
15 mph. The exception is this afternoon and evening, when gusty
northwest winds should occur, especially northeast of Tucson and
across the Upper Gila River Valley including Safford. The
combination of the gusty winds and minimum relative humidity of 5 to
10 percent may create critical fire weather conditions in the
northern portion of Fire Zone 152 late this afternoon. However,
these conditions are not expected be widespread nor long-lived.

&&

.PREV DISCUSSION /320 AM MST/...IR satellite imagery indicated
scattered debris cloudiness across southeast Arizona this morning.
As such, surface temperatures were still quite warm, as much as 5
degrees warmer than 24 hours ago in some locations.

Drier air aloft moves in today through Saturday along with a slight
moderation in daytime high temperatures. Even so, highs will be
above normal and dangerously hot, with the Excessive Heat headlines
remaining in place through Sunday evening. Another concern for this
afternoon will be gusty NW winds in the Upper Gila River Valley
including Safford. MOS guidances over the last 24 hours have trended
upward with regard to wind speeds, but the inclination is that the
numbers are a bit overdone. However, wind speeds may cross the
threshold to create critical fire weather conditions. Even so,
decided against issuing a Red Flag Warning as conditions will likely
be very localized and short-lived. Please see the Fire Weather
section below for more details.

Dry conditions continue Friday into Saturday morning, with some
isolated showers and thunderstorms possible over the mountains along
the AZ/NM border on Saturday afternoon. Sunday into next week, high
pressure migrates to a much more favorable location to draw deeper
moisture into the region from the south. With that, we`ll see a
decrease in chances for dry lightning and an increase in convection
producing measurable rainfall, especially as we get into Monday and
Tuesday. The official forecast calls for isolated to scattered
showers and storms mainly from Tucson eastward to the AZ/NM border
starting Sunday and continuing each day next week through Thursday.
As per usual, the best precip chances will be across the higher
elevations including the White and the Chiricahua Mountains.

As expected, it usually takes a long stretch of very hot
temperatures to kick-start the monsoon, and we should see exactly
that happen over the week. Additionally, we`ll get a well-deserved
break from the extreme heat, with highs dipping below warning and
advisory criteria on Monday/Tuesday and dropping even further to
near-normal by next Wednesday/Thursday.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
 Heat Advisory until 7 PM MST Sunday for AZZ510>514.

 Excessive Heat Warning until 7 PM MST Sunday for AZZ501>509-515.

&&

$$

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