Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 300924
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
224 AM MST Thu Mar 30 2017

.SYNOPSIS...Warmer today ahead of a storm system that will bring
increasing winds Thursday afternoon and tonight, with stronger winds
Friday east of Tucson. We`ll also see another chance of showers
mainly northeast of Tucson Friday and Saturday with a return to
cooler temperatures. Temperatures will then rebound to seasonal
averages early next week.

&&

.DISCUSSION...Clear skies this morning across southeast Arizona with
shortwave ridging aloft passing through the area. The next system
in this amplified pattern is now seen on WV satellite imagery
digging down into northern California. As this system continues to
track southeast into the Greats Basin today, the pressure gradient
will start to tighten with gusty west to southwest winds this
afternoon. Meanwhile, the warmest temperatures of the week are in
store this afternoon with highs about 7 to 10 degrees above normal.

For tonight, as the trough closes off into an anomalously strong
upper low and moves into far northern Arizona, the pressure gradient
will remain tight across the area with gusty winds continuing
through the evening and overnight. A surface cold front will also
track east to southeast across the forecast area from late this
evening through Friday morning. There are still some minor
differences in the timing of the front amongst the models with the
ECMWF seemingly the slowest with also the highest moisture fields.
Regarding QPF, the ECMWF is all alone in showing a few hundredths of
an inch along the cold front with the NAM/GFS and even all members
of the SREF and GEFS dry. Given the strong dynamics and forcing with
the front, am a bit concerned we will have a similar scenario play
out to Tuesday morning with a few showers along the front far enough
southwest to include the Tucson Metro early Friday morning. However,
given the near overwhelming guidance against this scenario will
leave out mentionable PoPs except for the mountains where we will
indicate slight chances. Later shifts will need to continue to
monitor.

With the front clearing out of the forecast area completely by
midday Friday, that will leave us with much cooler temperatures with
highs running about 10 to 20 degrees cooler than today. The upper
low itself will be located across northeast Arizona which will be
close enough for the chance of a few showers mainly across the
higher terrain of Graham and Greenlee Counties. The other concern
Friday will be the strong gusty winds, particularly east of Tucson.
Winds will likely be close to advisory thresholds especially for the
southeast half of Cochise County.

As the upper low slowly transitions eastward into New Mexico on
Saturday, areas northeast of Tucson will remain close enough to the
low and its wrap-around moisture for a continued chance of a few
showers with continued cool temperatures. A few breezes are expected
Saturday afternoon for eastern areas but less than today and Friday.

By Sunday, the upper low will move far enough east to allow for
shortwave ridging to build back in with moderating temperatures.
Heading into early to middle portions of next week, the pattern will
become a bit more progressive with the next system Monday into
Tuesday remaining far enough north it shouldn`t impact our weather
much except for once again some increased breezes. Expect
temperatures to remain a few degrees on either side of normal.


&&

.AVIATION...Valid through 30/00Z.
SKC areawide. Sfc wind less than 10 kts thru 29/18Z. Aft 29/18Z,
NWLY sfc wind at 8-16 kts, with the strongest wind in the upper Gila
River valley near KSAD. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Afternoon breezes will continue today and
Thursday along with warmer temperatures. Another weather system will
then move in late Friday with gusty winds. Red flag conditions
possible Friday afternoon across far southern fire weather zone 152.
This system will also bring a chance of showers mainly northeast of
Tucson Friday through Sunday.

&&

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

&&

$$

GL

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