Wildfire in Arizona, July 1 to 19, 2017

Area Forecast Discussion
National Weather Service Tucson AZ
932 PM MST Fri Jun 30 2017

.SYNOPSIS...Dry conditions will continue through Saturday night.
Isolated to scattered afternoon and evening thunderstorms will then
occur Sunday into next Friday. The bulk of thunderstorms will be
east to south of Tucson. Daytime temperatures will generally be a
few degrees above normal into next week.

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.DISCUSSION...Clear skies across the area tonight. Current forecast
looked in good shape, so no updates necessary this evening. Please
refer to the additional sections for more details.

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.AVIATION...Valid thru 02/06Z.
Clear skies much of southeast Arizona into Saturday afternoon. The
exception will be mainly southeast of KTUS where a few clouds above
15k ft AGL may occur. Surface wind Saturday afternoon wly/swly 10-15
kts with gusts to near 25 kts. Surface wind variable in direction
less than 12 kts at other times. Aviation discussion not updated for
TAF amendments.

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.FIRE WEATHER...Dry conditions through Saturday. Daytime minimum
relative humidity will generally range from 5-15 percent area-wide.
Isolated to scattered afternoon and evening thunderstorms will then
expected Sunday into next Friday. The bulk of these thunderstorms
will be mainly east to south of Tucson. Thunderstorm outflows will
create gusty and erratic winds at times, and there is the potential
for new fire ignitions due to lightning. Otherwise, southwest to
northwest afternoon winds at 10-15 mph are expected into early next
week, with the strongest speeds northeast of Tucson and especially
in the vicinity of Safford.

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.PREV DISCUSSION...Broad upper ridge extends from well west of the
southern California coast eastward into the southern CONUS this
afternoon. This pattern will provide dry conditions through Saturday
night. Various 30/12Z numerical prediction models then depict an
upper pattern that will become more conducive to the development of
showers and thunderstorms starting Sunday and continuing during the
upcoming week.

In essence, high pressure aloft is progged to become centered
generally near the Four Corners region Tuesday and remain quasi-
stationary over the central Rockies into the latter part of next
week. There were differences amongst the various deterministic
solutions and even between high resolution models such as the Univ
of Arizona WRF-NAM and WRF-GFS regarding daily precip chance detail
for this forecast area.

As an example, the WRF-NAM was more aggressive versus the WRF-GFS
regarding precip potential especially for the Tucson metro area
Sunday afternoon/evening. As another example, the deterministic
ECMWF was generally for robust with available moisture and liquid
precip amounts versus the GFS through around the middle of next week.
Thereafter, the GFS/ECMWF were quite similar regarding the depiction
of better precip chances by next weekend.

At any rate, only minor adjustments were made to the inherited
gridded data PoPs through next Friday. In summary for this forecast
period, expect isolated to scattered showers and thunderstorms, with
the best precip chances east-to-south of Tucson. The bulk of these
showers/tstms will occur during the afternoon and evening hours,
although some showers/tstms may occur during the late night/early
morning hours as well.

High temperatures this forecast period will generally average at
least a few degrees above normal.

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.TWC WATCHES/WARNINGS/ADVISORIES...None.

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