Heat in Arizona, June 27, 2021

Area Forecast Discussion
National Weather Service Tucson AZ
945 AM MST Sun Jun 27 2021

.SYNOPSIS...Hot and dry for most of the area today. The exception
will be for areas east of Willcox as an increase in moisture will
bring a chance for late day showers and thunderstorms. Then
moisture will increase across all of southern Arizona Monday
through the work week resulting in scattered showers and
thunderstorms and cooler afternoon temperatures.

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.DISCUSSION...Morning upper air plot and water vapor imagery
showed a weak upper trof over SW NM. At the surface the dewpoints
at 9 am were in the 40s from a Safford to Bisbee line east and in
the 30s west of this line. PW values across southern Arizona were
mostly around 0.75" with 1" values near the AZ/NM and over SW NM.
For today, the above mentioned trof over SW NM will be the focus
for isolated to scattered thunderstorms, mostly in SW NM, with our
far eastern areas, or east of a Safford to Bisbee line, on
western edge of activity. Outflows from these storms along with an
increasing easterly gradient will push low level moisture further
west across the forecast area tonight. Ran a quick update to the
today part of the forecast earlier this morning based on latest
model guidance. On the temperature side, it will be a hot one for
most of the area with areas from Tucson west in the 105-110 range.

Still on track for an active week as Monsoon 2021 gets into full
gear. More on this in the afternoon discussion but for now check
out previous discussion below for further details.

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.AVIATION...Valid through 28/12Z.
Generally SKC except FEW-SCT clouds 8k-12k ft AGL this afternoon
into the evening hours. Clouds locally BKN with ISOLD -SHRA/TSRA
east of Willcox this afternoon/evening. East-northeast SFC winds 5-
15 kts becoming northerly late this afternoon. Wind then becoming
easterly 10-18 kts this evening through tonight. Aviation discussion
not updated for TAF amendments.

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.FIRE WEATHER...One final hot and mostly dry day today with a
couple of showers or thunderstorms near the NM border area. Light
winds today will become easterly 10 to 20 mph this evening through
Tuesday forcing a welcome increase in moisture across the area. This
will result in a significant increase in humidity levels along with
an increasing amount of shower and thunderstorm activity through at
least next weekend. Initial convection this afternoon could be a
mix of wet/semi dry storms, however wet storms will be the
dominant mode later Monday and beyond. By midweek, there is the
potential for a few strong or slow moving storms to produce
locally heavy rainfall which could be a problem with burn scars
across the region.

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.PREVIOUS DISCUSSION...Monday: PW values continue to increase into the 1" to 1.5" range
per GEFS/EPS ensemble while the above mentioned trof transitions
into an easterly wave. Scattered showers and thunderstorms to
most of the forecast area. The exception will be wrn Pima county.
One thing to watch will be storms moving off the Rim Country south
and southwest into the Tucson Metro with plenty of DCAPE.
HRRR/NAMNEST hinting at this solution, which could result in
storms with strong wind gusts. Something to watch as more CAMS
come into play later today.

Tuesday and Wednesday: These two days are beginning to look like
the more active days of the week. An inverted trof will move from
east to west across the area, while upper level flow is out of
the southwest with modest speeds. This will allow for storm
motion to move into the moist/unstable airmass without being anvil
shaded. The slow movement of the trof will likely allow for Wed
to be quite active as well with strong enough moisture transport
to keep the area charged.

Thursday and Friday: The 700-300mb flow weakens and turns more
southerly while the upper level flows also weakens across the
area. However deep moisture remains in place. There will likely be
at least isolated to perhaps scattered showers/storms, but
overall activity could be down in the wake of the inverted trof
and possibly overworked atmosphere. Tough to tell this far out,
but we are trying to nail down the more active days. The NBM is
showing very high POPs each day, which is not realistic given the
lack of stronger forcing the second half of the week and past
history.

&&

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

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