912
FXUS65 KTWC 170922
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
222 AM MST Tue Sep 17 2024

.SYNOPSIS...

A few isolated showers and thunderstorms this morning diminish in
coverage by the late morning hours. Breezy, dry, and a few
degrees cooler than normal through the work week. Temperatures are
forecast to warm above normal again late this weekend.

&&

.DISCUSSION...

In the upper levels this morning, a deep trough was centered over
Nevada into far southern California, while a jet streak was
ejecting through the base of trough into Arizona and Utah. While
low to mid level moisture remained over southeastern Arizona, a
precipitable water gradient evident on the GOES TPW product was
advancing eastward this morning into central Pima county. The
eastward dry air push associated with the southwesterly flow of
the trough will effectively cut off precipitation chances by late
this morning, though coverage has already been diminished by the
top- down moisture erosion ongoing over the previous couple days.
As for sensible weather this morning, early cloud cover should
gradually erode after sunrise as the deepening boundary layer
mixes down dry air. Any lingering shower or thunderstorm chances
will shrink from south to northeast, with some final activity
possible in northern Graham and Greenlee counties into the early
afternoon hours. The tightened pressure gradient aloft and
unidirectional flow to the surface will promote breezy southwest
winds with gusts to around 30 mph during the day today. The
crossing jet streak and associated frontal passage will also bring
high temperatures to 3 to 5 degrees below normal this afternoon.

Temperatures remain a few degrees below normal through the work
week under persistent western CONUS troughing. That should allow
for morning lows to fall into the 50s over normally colder
eastern/southern valleys, and low to mid 60s in and north/west of
Tucson. A shortwave will likely cross Arizona on Saturday, though
weaker and more open than the early week version. Moisture return
looks unimpressive which keeps the forecast dry. Ensemble height
anomalies return to near to above normal Sunday onwards, leading
to an above normal temperature forecast into next week.

&&

.AVIATION...Valid through 18/12Z.

Clouds generally SCT-BKN 4k-8k feet this morning, decreasing in
coverage after sunrise. Isolated showers and thunderstorms this
morning follow the same trend, with a few lingering near and north
of KSAD late morning. Surface winds expected to increase to 10 to
15 kts with gusts to 25 kts and become southwesterly today. Winds
become light and terrain driven after 18/03Z. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...

Crossing low pressure today brings in dry air, breezy winds, and
temperatures 3 to 5 degrees below normal. Winds are expected to
become southwesterly and increase to 12 to 18 mph with gusts to
30 mph. Lingering moisture keeps minimum relative humidities from
falling too quickly today, but valley locations are forecast to
fall to the 15 to 20 percent range this week and 10 to 15 percent
as temperatures warm again this weekend. Winds will be breezy each
day before diminishing by the weekend.

&&

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

$$

Public...Edwards
Aviation...Edwards
Fire Weather....Edwards

Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson