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000 
FXUS65 KTWC 282228
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
328 PM MST Fri Apr 28 2017

.SYNOPSIS...A storm system north of the area will generate strong
gusty winds into the evening hours. For Saturday, winds will 
still be elevated but not quite as strong. Blowing dust may be an 
issue, especially in the vicinity of Interstate 10 with showers 
and a few thunderstorms possible well northeast of Tucson. Cooler 
temperatures Saturday and Saturday night, followed by dry 
conditions and a strong warming trend next week.

&&

.DISCUSSION...Our amplified / windy pattern continues as a strong
ridge off the west coast and a solid trough through the 
intermountain west squeeze our gradient like Homer clutching the
last donut. Seeing gusts in the 45-50 mph range in the advisory 
areas generally east and south of Tucson, with gusts 30-40 mph
elsewhere. Dew points in the 40s and precipitable water values
around 3/4 of an inch mean we have enough moister for a few 
showers mainly northeast and east of Tucson this afternoon and 
evening. Much drier air is already pushing into the area from the 
north however, with the Phoenix dew point down to 19 and Casa 
Grande 30.

Winds will diminish overnight, but remain gusty in some 
locations. Cooler tonight, but the winds and patchy cloud cover
will keep temperatures near average for late April.

The low sagging through the 4 corners area this evening will drop
into western New Mexico tomorrow. A brisk northwesterly flow on 
the back side of this feature will still see breezy to windy 
conditions for our area. Much drier, so even with the cooler 
temperatures we will still have some critical fire weather 
concerns tomorrow as outlined below. The direction of the winds
will mean blowing dust issues near I-10 should be less of a
problem.

Rapidly diminishing winds tomorrow night as the low moves east and
causes problems in the central and southern plains. That will
allow the much cooler airmass to bring the coolest overnight lows
since early April or late March. A freeze is possible in colder 
valley locations east and south of Tucson, primarily in Cochise 
county.

The strong ridge shifts from the eastern Pacific into our neck of
the woods next week. Temperatures will jump in response, and we
may be flirting with the first 100 at TIA by next Friday or so.

&&

.AVIATION...Valid through 30/00Z.
FEW-SCT 10K FT AGL with BKN-SCT clouds above 20k ft AGL becoming FEW-
SCT 10k ft, SCT above 20k ft after 29/03Z. SW-W SFC wind 20-30 kts 
with local gusts to 40 kts through 29/02Z then wind slowly easing 
through the night. Local areas of blowing dust into this evening. 
SFC wind NW 10-20 kts with gusts to 30 kts Saturday afternoon. ISOLD-
SCT -SHRA NE of KSAD until 29/18z. Aviation discussion not updated 
for TAF amendments.

&&

.FIRE WEATHER...Strong gusty winds will be slow to settle down 
tonight and many of the open and normally windy areas and ridges 
will remain breezy through the night. Clouds trimmed a few mph off 
the top but ended up rather windy despite that. The moisture 
increase was rather dramatic this afternoon with dewpoints well into 
the 40s and a few 50s are out there.  However, the dry air has 
started to invade western Pima county the last hour or two and will 
eventually sweep across the entire area through the night with 
humidity levels actually dropping for most of the night which is not 
normal. This includes the Sawmill fire area. 

Saturday will be very dry with RHs dropping to 8-12% valley areas 
despite the cool temps. Also expecting a decent breeze to continue 
across eastern areas, likely exceeding Red Flag criteria, thus the 
watch has been upgraded to a warning for parts of zones 151 & 152. 

Beyond that, wind will not be a problem Sunday onward however the 
air mass will be very dry with single digit afternoon RH levels and 
the temperatures will gradually climb from near normal Sunday to 10-
15 degrees hotter than normal by the end of the week.

&&

.CLIMATE...Based on current forecast temperatures for Tucson
through Sunday, April 2017 is pretty much locked in as the 4th 
warmest April on record.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 8 PM MST this evening for AZZ503>514.

Blowing Dust Advisory until 8 PM MST this evening for AZZ508-509-
511-512.

Red Flag Warning until 8 PM MST this evening for AZZ150>152.

Red Flag Warning from 11 AM to 8 PM MST Saturday for AZZ151-152.

&&

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