Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tucson Arizona
209 PM MST Friday may 22 2015
Synopsis...a low pressure systems moving north of the area will
bring gusty winds and cooler temperatures through Saturday. Below
normal high temperatures will continue through the weekend with a
warming trend beginning around the middle of next week.
Discussion...water vapor imagery shows an upper low spinning over
the general vicinity of southern Nevada. Ahead of this system infrared and
visible satellite imagery shows extensive cloudiness over much of
Nevada and Utah...as well as northern Arizona. Closer to home...
mostly just few to scattered high clouds over Southeast Arizona.
Main concern for the remainder of this afternoon and evening are
strong and gusty winds...especially over the eastern half of Cochise
County where a red flag warning has been posted and continues
through 7 PM MST this evening. See the fire weather section below
for more details.
Models indicate that the aforementioned upper low will move to the
east northeast over The Four Corners region by late afternoon
Saturday...with the associated trough axis draped across Arizona and
New Mexico. The moisture associated with this system should remain
mostly over northern Arizona and areas farther to the north.
However...a secondary vorticity maximum rotating around the back side of the
low will swing through southern Arizona and northern Sonora Sunday
through early Monday. This will result in mainly just a slight
chance of showers for the White Mountains beginning late Saturday
and continuing through early Monday. Otherwise...dry elsewhere with
the passage of this weak system.
Weak ridging will build in behind this system early next week before
another trough approaches from the west. Limited moisture associated
with this system...at least for Arizona. Models are at odds with
where to depict the associated moisture...with the GFS showing the
moisture residing mainly just east of the New Mexico border on
Thursday and then shifting eastward through Friday. European model (ecmwf) shows the
moisture much farther east over eastern New Mexico and northern and
central Texas. That said...opted to maintain a dry forecast through
next Friday. Stay tuned.
For Tucson...high temperatures generally around 10 to 15 degrees below
normal for Saturday...then around 5 to 10 degrees below normal Sunday
and Monday. Thereafter...highs only slightly below normal Tuesday
through Thursday and near normal by Friday. Lows will be around 6 to
8 degrees below normal this weekend...then 3 to 5 degrees below normal for
Monday morning. Thereafter...lows just slightly below normal each
Aviation...valid through 24/00z. Few-scattered high clouds above 20k feet above ground level
with decreasing coverage overnight. Surface winds the remainder of
this afternoon will generally be southwesterly 15-25 kts with gusts to 35 kts
before decreasing after 23/02z. More typical terrain-driven winds
less than 12 kts will return tomorrow afternoon with a few gusts to
20 kts possible...mainly in the vicinity of kdug. Aviation
discussion not updated for taf amendments.
Fire weather...the primary focus for today continues to be the
combination of strong southwesterly winds and low minimum relative
humidity values...reaching critical thresholds mainly across parts
of Cochise County...and a high fire danger rating. As a result...a
red flag warning continues across southern fire weather zone 152
until 7 PM this evening. More localized and brief critical
conditions can be expected over southern portions of zone 151.
Slightly cooler temperatures and much less wind are expected on
Saturday with any lingering gustiness confined to areas mainly east
of Tucson. A slight chance for showers and thunderstorms exists
across the White Mountains on Sunday. Thereafter...a warming trend
is forecast with high temperatures warming back to near-to slightly
above-normal readings through the end of next week.
Twc watches/warnings/advisories...red flag warning until 7 PM this
evening for southern fire zone 152 or eastern Cochise County.
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