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000
FXUS65 KTWC 090955
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
255 AM MST Tue Apr 9 2024

.SYNOPSIS...A weak weather system aloft will result in a slight
chance of very-light showers for portions Southeast Arizona
today. This will allow temperatures to remain below normal for
one more day before a strong warming trend is expected for the
second half of this week. This warming trend will likely result in
Tucson seeing its first 90 degree temperature of the year.

&&

.DISCUSSION...A weak upper low over the International Border in
Santa Cruz/Cochise counties will track east across Northern
Chihuahua/Southern New Mexico today. Not much moisture with this
feature, but it is cool enough to squeeze out a slight chance of
very-light showers across South central Arizona this morning. As
this feature tracks east today, weak instability may wrap back
around into the White Mountains this afternoon with additional
light showers and possibly a weak thunderstorm. This is a low
confidence event though as the pace of the upper low moving east
may outpace any disturbance wrapping around into the area. In any
event, this weak system will not be very impactful.


The big forecast story is what happens next. An amplified ridge
off the coast of California will work its way into the Desert
Southwest the next few days, with the ridge axis moving through
our neck of the woods Thursday afternoon. This ridging will
likely bring the first 90 degree day to the Tucson Metro Area
Thursday. The NBM probability of meeting or exceeding 90 degrees
in KTUS is 68% Thursday and 44% Friday. This matches up with our
local regression equation that suggests an 850-700 mb thickness of
1640 m seen on the GFS and ECMWF deterministic runs will result
in a high temperature of 91 degrees in April. So, I am confident
we will see our first 90 degree day this week. Although this
doesn`t equate to a record or near record high, it will be
impactful because of how cool Southeast Arizona has been
recently. It`s probably a good idea to pass along heat related
messaging to those that may not be expecting this warmup.

In any event, a weak dry upper low behind this ridge will eject
through the area Friday bringing with it some breezy conditions,
with another more substantial upper low digging south along the
West Coast this weekend. It would be climatologically normal for
this feature to be dry as it ejects north of our area early next
week, resulting in yet another round of breezy conditions.


&&

.AVIATION...Valid through 10/12Z.
SCT-BKN clouds AOA 10k ft AGL with a slight chance of -SHRA south
and southeast of KTUS. There is low confidence in a slight chance
for -SHRA with infrequent lightning strikes near the White Mountains
in East Central Arizona this afternoon. Otherwise, SFC winds light
and variable increasing to around 10kts in the afternoon hours
from the northwest with gusts up to 20kts. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...A weather system will bring slight chance of very-
light showers near the International border this morning. Minimum
relative humidity values mostly 10-20 percent through Tuesday
then drop to under 10 percent for the lower valleys Wednesday into
Friday. High temperatures remain below normal today before
warming up to above normal readings Wednesday through Friday, with
Thursday the warmest of the three days. Gusty winds return Friday
into the weekend as another system moves through. A few localized
areas could see brief Red Flag conditions, but fire danger and
ERCs are low for this time of year.

&&

.CLIMATE...First 90 degree high date information for Tucson
Historical period (1895-2023): April 8th
Climatological normal period (1991-2020): March 30th
2023 1st date: April 10th

&&

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

&&

$$

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