796
FXUS65 KTWC 082145
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
245 PM MST Mon Jul 8 2024

.SYNOPSIS...Excessive heat continues through mid-week with high
temperatures expected to approach record levels in some locations.
The combination of substantially drier air and a stable
atmosphere will reduce thunderstorm chances today. Returning
moisture and a more favorable weather pattern will result in
thunderstorm chances returning Tuesday and increasing through the
week.

&&

.DISCUSSION...Excessive heat. Its almost a broken record at this
point, but it remains significantly impactful for Southeast
Arizona not only today but well into this week. The 08/13Z NBM
probabilities for Tucson exceeding 110 degrees this week are 80%
today/55% Tuesday/55% Wednesday/55% Thursday and 25% Friday. We
are running approximately 1 to 5 degrees warmer than this time 24
hours ago across the CWA, with KTUS already reaching 111 degrees
at 231 pm MST. The record high temperatures for KTUS today is 111
degrees last set in at 1994.

With regards to thunderstorm activity, today will be a quiet day
across the entire forecast area. The SE extent of the upper ridge
centered over central California will be just too much warm air
for us to overcome this afternoon. Surface dewpoints are awful
today, with KSAD mixing down so far to 22 degrees, and KDUG and
KTUS down to 43 degrees. Not the most favorable conditions for
afternoon convection. No storms today with some cumulus
developing near/over the higher terrain.

This will begin to change as we move through the week though. A
N/S oriented jet streak seen on the eastern periphery of the upper
ridge this morning will assist in the re-orientation of this
feature from a negative tilt this morning to a more neutral tilt
Tuesday. As this occurs, areas east of Tucson will start to see
an area of weak diffluence and stretching deformation aloft,
which will in turn assist in the overall lift. In addition, CAMS
are suggesting an outflow from storms in NM today will import
lower level moisture into the eastern locales/upper Gila River
Valley overnight. The combination of these two things will bring
back thunderstorm activity east of Tucson tomorrow. With the
excessive heat in place and pockets of dry air in the middle
levels, the threat tomorrow will be from strong thunderstorm
outflows. At this stage, I dont believe the extent of any outflows
impacting locations as far west as Tucson will occur tomorrow.
However, as the upper high shift more to the north and east with
time, this allows for the more favorable NE flow from storms to
march from the Rim down toward our neck of the woods. Expect
thunderstorm coverage to expand west across the rest of the CWA
beginning Wednesday and continuing into the weekend.

Late this weekend into early next week, the upper High is expected
to move over Colorado. This position would open Southeast Arizona
up to an easterly flow. There are indications that point to an
inverted trough making its way into southern New Mexico Sun day
and Monday. If this were to happen, not only would we see an
increase in moisture from the east and south, but dynamics will be
present for more widespread precipitation Sunday and Monday. There
is still some uncertainty in where that upper high eventually
moves to, but things are starting to look wet as we move into
early next week. Stay tuned.

&&

.AVIATION...SKC across the majority of southeast Arizona with
the exception of SCT cumulus above the higher terrain. Areas near
KDUG and the New Mexico border SCT-BKN 7-10k ft AGL are possible
feet are possible with a slight chance of a thunderstorm through
the evening. Skies will become SKC this evening and overnight. SFC
Winds west to northwesterly 10 to 15 kts with occasional gusts to
20-25 kts, decreasing after sunset. Aviation discussion not
updated for TAF amendments.

&&

.FIRE WEATHER...Excessive heat will persist this week across the
majority of Southeast Arizona. This afternoon should see the
lowest minimum relative humidities of the week as moisture is
expected to gradually push back into southeastern Arizona in the
coming days. Relative humidity values should fall into the single
digits in lower elevations today, while west to northwest winds of
12 to 16 mph with gusts up to 25 mph are expected. Tuesday
through Thursday minimum relative humidities should remain in the
10 to 16 percent range in lower elevations and 15 to 30 percent in
mountain areas. 20-foot winds will generally be 15 mph or less
each afternoon with occasional gusts to 20 mph. Daily chances for
thunderstorms begin to arrive Tuesday, with the possibility of
strong outflow winds under any thunderstorm.

&&

.CLIMATE...
Near record to record high temperatures today, Tuesday, and
Wednesday.

DATE                         Jul 08           Jul 09           Jul 10
                          FCST RCD/YR      FCST RCD/YR      FCST RCD/YR
TUCSON INTL AIRPORT       111 111/1994     110 110/1979     109 109/2021
PICACHO PEAK              114 114/2017     114 113/1994     113 111/1995
SAFFORD AG STATION        110 107/2002     106 108/1956     106 110/2003
SIERRA VISTA FD           102 102/2023     100 103/2003     100 102/2003

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST Wednesday for AZZ501>506-509.

&&

$$

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