Area Forecast Discussion
Issued by NWS Tucson, AZ

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676
FXUS65 KTWC 220340
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
840 PM MST Wed Jun 21 2017

.SYNOPSIS...Expect very hot and near record temperatures into this
weekend. Dry conditions will prevail Thursday into Friday, then a
more favorable pattern will provide scattered afternoon and evening
thunderstorms especially by Sunday and continuing into the middle of
next week.

&&

.DISCUSSION...The bulk of the convection today occurred across the
higher terrain to the south and east of Tucson. Although slow
moving, the storms were relatively minor rain producers with
most locales seeing less than a quarter inch. As expected,
given the dry sub cloud mixed layer as depicted in the inverted-v
profile on the 00Z KTWC sounding, gusty outflow winds up to about 40
MPH with some blowing dust was the main impact.

Latest KEMX radar imagery shows the leftover showers east of Tucson
have just about completely dissipated as cloud tops are warming
rapidly. We`ve gone ahead and updated the forecast for the remainder
of tonight to remove mentionable PoPs. Otherwise, cloud coverage
from Tucson eastward is expected to diminish overnight with clear
skies continuing west of Tucson. Drier air aloft moves in for
Thursday shutting down precipitation chances. Besides the
continued heat Thursday, the other concern will be gusty NW winds in
the Upper Gila River Valley including Safford which could create
critical fire weather conditions. For additional forecast
information, see previous discussion below.

&&

.AVIATION...Valid thru 24/06Z.
SCT-BKN clouds from KTUS eastward mainly 10k-15k ft AGL this
evening, giving way to clouds 10k-15k ft AGL late tonight into
Thursday. Surface wind  diminishing to less than 10 kts this evening
and continuing into Thursday morning. Surface wind Thursday
afternoon nwly 10-25 kts with gusts to 35 kts. The strongest speeds
will be northeast of KTUS and especially near KSAD. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Dry conditions will then prevail Thursday into
Friday, and across much of the area Saturday. The exception is near
the New Mexico border where a slight chance of thunderstorms may
occur.

Thereafter, a favorable pattern for thunderstorm development will
return Sunday and continue into the middle of next week. Scattered
afternoon and evening thunderstorms should prevail, especially east
to south of Tucson. However, the coverage of thunderstorms Monday
into Tuesday should expand further west to also encompass Fire Zone
150 west of Tucson.

Otherwise, 20-foot winds will generally be terrain driven less than
15 mph. The exception is Thursday 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 Thursday afternoon. However,
these conditions are not expected at this time to be long-lived.

&&

.CLIMATE...
Daily record highs Thursday

                         June 22

                          RCD/YR
TUCSON INTL AIRPORT      114/1988
BISBEE-DOUGLAS AIRPORT   106/1990
AJO                      115/1960
FORT THOMAS              112/1961
KITT PEAK                 92/1988
ORGAN PIPE CACTUS        113/1955
PICACHO PEAK             113/1988
SAFFORD AG STATION       108/1960
SIERRA VISTA FD          104/2012
TOMBSTONE                109/1929
WILLCOX                  106/1990

&&

.PREV DISCUSSION...Tomorrow will see slightly drier air enter the
area although several deterministic model runs are still suggestive
of lingering BL moisture across central Pima Co as well as the White
Mtns. PoPs haven`t been cleared out entirely but the overall trend
should be one of fewer showers and storms across the area. It`ll
also be breezier across the area, today`s MOS guidance near Safford
is suggesting winds around 30kts but those values are on the high
end of the spectrum and readings between 10-20kts seems much more
realistic. It doesn`t appear winds will be strong enough to
necessitate a Wind Advisory (or a Red Flag Warning) for that matter
but conditions will remain less than idea for firefighting efforts
across the region.

Another trend worth noting is a slight reduction in temperatures as
nearly all blended bias corrected guidance along with NBM data are
showing temps a few degrees lower. Highs will still be dangerously
hot with readings around the 110 degree mark and the heat warnings
and advisories will remain in effect.

Friday and Saturday should be mostly dry with only some cu/isolated
showers over the mountains along the AZ/NM border. Looking to Sunday
and beyond we should see a substantial increase in moisture across
the area (BL mixing ratios climbing to around 10-12 g/kg). Mountain
showers and storms that are actually capable of producing measurable
rainfall seem like a virtual certainty by early next week with the
lower deserts seeing increasing chances as well. A bit of an earlier
than normal start to the convective portion of the monsoon but
that`s not too surprising given the ongoing stretch of near record
temps.

&&


.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.

&&

$$

GL

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