148
FXUS65 KTWC 292028
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
128 PM MST Sat Jun 29 2024

.SYNOPSIS...Active monsoon pattern this weekend into early next
week bring daily chance of showers and thunderstorms. Some storms
will generate strong winds and locally heavy rainfall.

&&

.DISCUSSION...Latest visible satellite imagery early this afternoon
is still showing quite a bit of mid level clouds across most of
southeast Arizona as an MCV is pushing north from Santa Cruz/SW
Cochise County. This cloudiness has kept temperatures from warming
up as quickly as usual today and depending on how much persists into
the mid afternoon hours, may keep Tucson below 100 degrees today.
It`ll be a close call. Not much on radar at this time with just a
few light showers mainly east of Tucson. Given the placement of the
MCV and subsidence behind it as the MCV pushes north, convective
development is on the slow side today. Latest HRRR shows a few
storms mainly west of Tucson through the afternoon and this is where
more abundant solar insolation has occurred today. Elsewhere, a
continuation of some scattered shower activity with perhaps an
embedded thunderstorm or two that could produce brief heavy rain.
All in all, certainly a much quieter afternoon period than what we
experienced yesterday.

Heading into this evening and the overnight hours, our focus shifts
toward the disturbance currently seen on WV imagery over Chihuahua
that is pushing to the west-northwest. This will help trigger
convection across NE Sonora/NW Chihuahua early this evening that
will push to the northwest later in the evening and overnight hours.
The convection will be aided by the deep layer lift from the
aforementioned disturbance, along with outflow boundaries acting on
elevated CAPE. Don`t be surprised if you hear rumbles of thunder in
Tucson in the midnight to 3 am time frame. This area of convection
will also help reinforce the deep moisture over our area. Latest
HRRR/CAMs show convection winding down around or shortly after 12Z.

Sunday into Sunday night is shaping up to be a very active period.
Sunday morning cloud cover should diminish fairly quickly as 15 to
20 kt southeasterly flow aloft pushes clouds from the overnight
convection away and allows the atmosphere to reload. The combination
of increasing instability (MLCAPE at or above 1000 J/KG in many
locales), and another disturbance approaching aloft will set the
stage for widespread shower and thunderstorms Sunday afternoon into
evening. Most of the forecast area is at risk for these storms,
though the focus for the strongest storms and greatest flash flood
risk will be from western Cochise County to points westward
including Tucson Metro and into the Tohono O`oodham Nation. HREF 3
hour QPF 40km neighborhood probabilities exceed 70% for 1 inch or
and around 10% for 3 inches or more near the Tucson Metro. WPC has
the area referenced above already outlined in a slight risk for
excessive rainfall and that continues to look good. Greatest concern
for flash flooding will be due to storm mergers/clustering as
individual storm motion will be around 15 mph. Later shifts will
need to consider hoisting a Flash Flood Watch for portions of the
forecast area. There is also a threat for strong gusty outflow winds
Sunday afternoon into evening, especially from Tucson and point
north and westward where DCAPE values exceeding 1500 J/KG will
assist in the development of these strong outflows. HREF members are
all in agreement of this scenario with strong outflows pushing NW
across Pinal County which would result in areas of blowing dust.
This is also something we`ll be monitoring.

The disturbance that is expected to result in the widespread
convection Sunday will move to our north by Monday with the flow
aloft a bit more from the south to southwest. We`ll have to see just
how worked over the atmosphere is and how much subsidence there is
on Monday for less convective activity. Given the flow pattern, the
focus will tend to be on areas from Tucson eastward.

The active and moist pattern will continue into the middle of the
week and through July 4. However, it`s a little bit challenging to
discern the more active days/locations at this time. By Friday and
into next weekend as the high aloft reestablishes itself and
strengthens to our north, our flow pattern will be more from the
NE/ENE and this would be more favorable to bring storms in off the
Mogollon Rim/Gila Mtns, a pattern we have yet to see this monsoon.

&&

.AVIATION...Valid through 01/00Z.
SCT-BKN clouds at 8-12k ft AGL thru the fcst period. SCT-SHRA/-TSRA
with brief MVFR conds nr storms, most likely between 30/03Z and
30/11Z and then again aft 30/20Z. SFC winds 10 kts or less with the
occasional afternoon gusts, except stronger due to gusty outflows
from storms. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Relatively deep moisture will stick around through
the forecast period. This will bring scattered thunderstorms and
showers this afternoon and especially tonight with an uptick in
thunderstorms Sunday afternoon/evening. Next week will see daily
chances of afternoon and evening showers and thunderstorms. Strong
erratic gusty winds of 40 mph or higher can be expected with any
storm development, along with locally brief heavy rainfall. Outside
of thunderstorm winds, 20-foot winds will generally be 15 mph or
less each afternoon with the occasional gust of 20 mph. Min RHs will
generally be around 20% in the valleys and 30s in the mountains with
good overnight recoveries.

&&

.CLIMATE...The triple-digit high streak for Tucson, which
currently stands at 33 consecutive days, is at risk today thanks
to yesterdays two brief heavy rain events that hit the airport and
cloud cover.

&&

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

&&

$$

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