Severe Thunderstorm Warning 307, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
136 PM MST Fri Aug 16 2024

.SYNOPSIS...There will be a daily chance of mainly afternoon and
evening showers and thunderstorms through next week across southeast
Arizona. The thunderstorms will be accompanied by the typical
monsoon threats of strong wind gusts, localized heavy rainfall and
flash flooding and blowing dust. High temperatures will be several
degrees above normal into at least the middle of next week.

&&

.DISCUSSION...In the larger picture, high pressure aloft centered in
east central New Mexico will move northeast into northeastern New
Mexico by Saturday and then remain quasi-stationary between northern
New Mexico and the Texas panhandle through next week. This will keep
southeast Arizona in a favorable south-southeast flow pattern for
shower and thunderstorm development. The models show some drier
air gets trapped under the upper high and spreads across our eastern
counties (Graham and Cochise) Sunday into Tuesday, which could limit
thunderstorm activity in those areas on those days. With the upper
high in close proximity, positive height anomalies will lead to high
temperatures being 3-6 degrees above normal through at least the
middle of next week.

For this afternoon and tonight: A very slow start to convection
today as expected. The University of Arizona WRF model and other hi-
res models continue to indicate that isolated to scattered showers
and thunderstorms will develop this afternoon and then continue well
into evening hours tonight across much of southeast Arizona. The
main threats will be strong wind gusts and localized heavy
rainfall/flash flooding and blowing dust.

Saturday and Sunday: Both days appear active, with Saturday being
the most active. Drier air edging in from the east on Sunday will
limit convection over portions of Cochise and Graham counties.
However, scattered showers and thunderstorms are still expected west
of a Sierra Vista to Oracle line on Sunday. Strong (to severe) wind
gusts and heavy rainfall/flash flooding will be possible both days
with the stronger storms. The thunderstorms will initiate over the
higher terrain and then move to the west/northwest into the
lower deserts with a southeast steering flow.

Monday and Tuesday: The models show the drier air pushing westward
across the eastern counties limiting thunderstorm activity. Isolated
chances for much of the forecast area, with the highest POPs from
Santa Cruz County westward across central Pima County.

Wednesday through Friday of next week: Deeper moisture returns to
southeast Arizona, as a trough develops along the west coast and the
flow turns more southerly across Arizona. A standard monsoon
forecast of isolated to scattered mainly afternoon and evening
showers and thunderstorms for these days at this time.

&&

.AVIATION...Valid through 18/00Z.
FEW-SCT clouds at 6K-9k ft AGL becoming SCT-BKN clouds at 6k-9k ft
AGL and BKN-OVC clouds AOA 15k ft AGL by 16/23Z, with ISOLD-SCT
SHRA/TSRA thru 17/06Z, then slowly clearing skies thru 17/17Z. Aft
17/17Z, SCT-BKN clouds at 6k-9k ft AGL and ISOLD-SCT SHRA/TSRA thru
the end of the forecast period. MVFR conditions near TSRA, with VSBY
restrictions, wind gusts to 45+ kts, heavy rain and mountain
obscurations. Outside of thunderstorm wind gusts, wind speeds will
be 12 kts or less, favoring a WLY/NWLY 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 daily chance of showers and
thunderstorms across southeast Arizona through next week. Saturday
looks to be the most active day in terms of storm coverage and
strength. High temperatures will be 3 to 6 degrees above normal
through the middle of next week. Min RH values will be in the 20-30
percent range in most valleys locations (lowering to near 15 percent
in eastern Cochise and the upper Gila River valley) through the
middle of next week. Outside of any thunderstorm outflow winds, 20-
foot winds will generally be 15 mph or less, with afternoon/early
evening gusts to 20-25 mph and light winds overnight.

&&

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

Zell

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