Severe Thunderstorm Warning 45, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
802 AM MST Tue Jul 2 2024

.SYNOPSIS...Chances of showers and thunderstorms today through
Wednesday, then gradually diminishing during the rest of the
week. Some storms will generate strong winds and locally heavy
rainfall. With high pressure building in from the northwest,
daytime temperatures will be trending hotter Thursday into at
least early next week.

&&

.UPDATE...The morning KTWC sounding still pointing at a busy day
for much of SE AZ. Precipitable water hanging in with 1.6 inches
to go with surface dewpoints in the 60s. Modest convective
inhibition that should be easily overcome with solid insolation
through the morning hours. Good convective potential for valleys
after an early start in the mountains, with initial development
over higher terrain by late morning hours. We put out a minor
update tweaking initial mountain convection a little earlier with
broader valley support in the afternoon. Some of the storms will
likely get frisky but we don't have the shear to support more
widespread organized convection. Possible convective complex in
Sonora this evening. Please see the previous discussion below for
additional details.

&&

.PREV DISCUSSION... /issued 235 AM MST Tue Jul 2 2024/

Clear to scattered mainly high level clouds was over the area
this morning under S/SW flow aloft per latest GOES-18 IR imagery.
PW values this morning ranged from 1.3" east to 1.6" west with
higher values over northern Sonora MX. For today, with more sun
around versus previous days, expect most of the area seeing
scattered showers and thunderstorms this afternoon/evening with
main threats once again being strong gusty winds and brief heavy
rain. Some CAMs are indicating Santa Cruz and Cochise counties
could be the focus of more areal coverage of storms later today.
There is some indication that outflows from storms in northern
Sonora MX this evening will push north into the area later tonight
developing some isolated elevated storms. Highs today at or a few
degrees above normal.

Wednesday will see reduced areal coverage of storms due to
decreasing moisture values as high pressure aloft, building over
California, turns flow aloft out of the N/NE. Still could see a
minor rim shot mainly east of Tucson Wednesday evening. Highs
similar to today.

Thursday into early next week...Strong high pressure aloft
building over CA/NV/AZ will be the driving force in drying out
and heating the area up. Expect minimal thunderstorm activity each
day with high temperatures heating up resulting in moderate to
major heat risk criteria being met. The initialized NBM
temperatures for Thu-Mon, in my opinion, are not hot enough.
Looking at in house low-level thickness study, I went with the top
end of the temperature spread, or the NBMs 95th percentile, for
high temperatures, and they still may not be hot enough. Daily
record highs will be approached starting Fri and continuing into
early next week. Held off on hoisting an Excessive Heat Watch in
this forecast package, but this is something for later shifts to
consider. Looking out to 10 days, or next Thursday, Excessive Heat
will continue.

&&

.AVIATION...Valid through 03/12Z.
FEW-SCT clouds at 9k-12k ft AGL and SCT-BKN clouds AOA 20k ft AGL
thru 02/17Z, then SCT-BKN clouds at 7k-10k ft AGL thru the remainder
of the forecast period. ISOLD-SCT TSRA/SHRA between 02/18Z and
03/05Z. MVFR conditions near TSRA, with mountain obscurations, VSBY
restrictions and gusts to 40+ knots. Otherwise, outside of TSRA
outflows SFC wind generally 10 kts or less, favoring a WLY/NWLY
direction during the afternoon/early evening and variable in
direction at other times. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...There will be the daily chance for isolated to
scattered showers and thunderstorms mainly from Tucson east and
south through the end of the week, with a slight chance of showers
and thunderstorms along the International Border this weekend into
early next week. High pressure aloft will build to our northwest
late this week into early next week, which will result in drier and
hot conditions. The deeper moisture will get pushed south and east
of the region late this week into early next week, with Min RH
values lowering into the 10-18% range across the lower elevations
and 15-30% in the higher elevations. High temperature will warm
considerably late this week through the weekend, with highs 106-113
degrees from Tucson westward and in the Gila River Valley, and in
the upper 90s to 105 degrees across Santa Cruz and Cochise counties.
Excessive Heat will likely be an issue during this time frame.
Outside of any thunderstorm outflow winds, 20-foot winds will
generally be 15 mph or less each afternoon with the occasional gust
of 20-25 mph.

&&

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

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