644
FXUS65 KTWC 140822
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
122 AM MST Sat Sep 14 2024

.SYNOPSIS...Increasing moisture will result in a chance of showers
and thunderstorms across southeast Arizona through Monday. The
highest chances and most widespread coverage will be Sunday and
Monday. Dry conditions return next Tuesday through the remainder of
next week. High temperatures will be right around normal today and
then several degrees below normal Sunday through the rest of next
week.

&&

.DISCUSSION...Very little change in the forecast versus 24 hrs ago.
Sure, model QPF and POP values have slightly different values, but
there are no significant changes in the latest large scale and/or
high-res models over the weekend and through next week. Tropical
Storm Ileana is currently in the mouth of the Gulf of California,
east of La Paz. This storm will weaken into a Depression late this
afternoon and make landfall Sunday afternoon near Ciudad Obregon.
While the main system stays well south of southeast Arizona, this
system will continue to push tropical moisture northward into our
forecast area. PWAT values will increase to 1.0"-1.25" this
afternoon and to between 1.25"-1.50" on Sunday, before decreasing
from west to east Monday afternoon into Monday night.

Weak convection occurred along the International Border south of
Nogales and Sierra Vista yesterday evening into the early overnight
hours in the deeper moisture axis pushing northward. While this
activity has temporarily died off, the high-res models show
convection firing back up between 1130-1230 today and then
persisting into the mid evening hours tonight. The NBM keeps the
bulk of the showers and thunderstorms today/tonight to the south and
southwest of the Tucson metro area, although there will still be a
slight chance of showers and thunderstorms in Tucson during the late
afternoon and evening hours tonight. Widespread showers and
thunderstorms are then expected Sunday and Monday. There will be the
potential for convection to persist through the evening and
overnight hours Sunday night. Forecasted rainfall amounts across
southeast Arizona through Monday will be between 0.15"-0.8", with
localized higher amounts due to stronger convection and in the
mountains. The EMC`s GEFS plumes for Tucson show values ranging
between 0.10" and 0.84", with a mean of 0.37".

Monday continues to look like an interesting and potentially very
active day as a closed low moves eastward across the Great Basin
providing extra dynamics and mid level shear to the equation. This
day has the highest potential for some of the storms to be severe,
along with heavy rainfall/localized flash flooding. This low will
then scour out the moisture across southeast Arizona late Monday
night/early Tuesday as it lifts northeast into the northern Rockies.
The models then show a secondary closed low dropping southward
through California Wednesday into Thursday of next week.

High temperatures will be right normal today, lowering to 2-3
degrees below normal Sunday and Monday and then 4-6 degrees
below normal Tuesday through Friday of next week.

&&

.AVIATION... Valid through 15/12Z.
FEW-SCT clouds at 6k-9k ft AGL becoming SCT-BKN clouds at 6k-9k ft
AGL by 14/18Z and persisting thru the remainder of the forecast
period. A chance of -SHRA/-TSRA between 14/19Z and 15/05Z. The
highest chance for -SHRA/-TSRA will be south of KTUS. MVFR
conditions with the stronger -TSRA, with brief ceiling and
visibility restrictions, mountain obscurations, localized heavy rain
and gusts to 40 kts. Outside of thunderstorm wind gusts, SFC wind
will be 12 kts or less and SWLY/WLY in direction during the
afternoon/early evening hours and variable in direction at other
times. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...There will be a chance of showers and
thunderstorms through Monday, with the highest chances and most
widespread coverage Sunday through Monday. Dry conditions return
next Tuesday and persist through the remainder of next week. Min RH
values today will be 20-30 percent in valley locations and 30-45
percent in the mountains, rising another 10 percent on Sunday and
Monday. 20-foot winds will generally be 15 mph or less through the
weekend, with the exception of gusty and erratic winds in/near
thunderstorms. South to southwest winds of 15-20 mph and higher
gusts will occur for much of next week, mainly during the afternoon
and early evening hours.

&&

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

&&

$$

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