050
FXUS65 KTWC 200943
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
243 AM MST Thu Jun 20 2024

.SYNOPSIS...Hot temperatures today with an Excessive Heat Warning
in effect for portions of southeast Arizona. Moisture will
increase Thursday resulting in the potential for thunderstorms
each day into next week week. Storms today could produce strong
winds and blowing dust mainly from Nogales to Tucson and into
Pinal County. Windy conditions are also expected today into
Friday. The added moisture will also result in temperatures
dropping back down to more seasonable levels.

&&

.DISCUSSION...An outflow boundary that originated in New Mexico
Wednesday afternoon is currently moving through Cochise and Graham
Counties. Behind it surface winds have turned easterly and dew
points are in the 50s. The leading edge looks to be just past
Wilcox. Hi-res models show this boundary continuing westward into
the afternoon making it as far as Tucson or just west of Tucson.
At the same time the surface pressure gradient will tighten thanks
to surface high pressure building over the Midwest and troughing
to the west. This will lead to strong easterly winds through
Friday with speeds 20 to 35 mph and gusts 35 to 50 mph area wide
with the strongest winds in the Gila River Valley and eastern
Cochise County. A Wind Advisory is in effect for those two areas.
High pressure aloft will be building back west leading to a
further increase in temperatures today with KTUS seeing a 63
percent chance to hit 110 degrees, which would be the first of the
year. An Excessive Heat Warning is in effect for Tucson and areas
north and westward.

Mid-level moisture also begins to increase today with PWAT values
increasing to around 1.3 inches by this evening. The HREF and
other CAMs are all in fairly good agreement showing a line of
storms forming mid-afternoon from Santa Cruz County north through
Tucson and into Pinal County. Convergence along the
aforementioned surface boundary will be the trigger for storms
aided by synoptic scale lift ahead of a shortwave trough over
southern California. CAPE values will range from 500-1000 J/kg
with 0-6 km shear as high as 35 kts. There will also be
directional shear with surface winds out of the southeast and mid-
level winds out of the southwest. Forecast soundings show an
inverted V signature with DCAPE values up to 2000 J/kg. Because of
this any storms that do form could produce strong winds with one
or two possibly producing severe winds. The HREF has a 30 percent
probability for 50 kt winds or greater from north Tucson into
Pinal County and 10 percent probability extending into Santa Cruz
County. Outflows from these storms could also produce blowing
dust, and as a result a Blowing Dust Advisory has been issued for
most of Pinal County.

Friday gusty easterly surface winds will continue with the
strongest winds still expected in the Gila River Valley. Moisture
advection will continue with PWAT values reaching up to 1.5
inches. The shortwave will move north and flatten out as the ridge
continues to build further west. Temperatures will moderate some
thanks to the moisture with highs about 3 degrees less than today,
although cloud cover and storms could prevent temps from reaching
their full potential. Mid-level flow will be weaker but
instability will still be between 500-1000 J/kg. The HREF shows
isolated thunderstorms tied mainly to the higher terrain. The main
threat will again be wind, but probabilities for strong winds are
less than Thursday with the HREF showing most of the area under
30-50 percent chance for winds 30 kts or greater.

This weekend into early next week the high becomes centered over
Arizona and the AZ/NM border. This keeps southern Arizona in
favorable mid-level easterly flow with PWATS ranging from 1.2"
along the AZ/NM border to 1.75" in central and western Pima
County. These values are approaching the NAEFS 99th percentile.
With the moisture staying in place expect each day to see isolated
to scattered showers and thunderstorms. Exact placement and
coverage will be dictated by the placement of ridge. Closer to
the center of the high convection will be stunted somewhat. The
main threat will continue to be strong outflow winds and
lightning, although some storms will be capable of locally heavy
rainfall if the boundary layer moistens up. Temperatures will be a
few degrees above normal through early next week and could be
moderated by thunderstorm activity.

&&

.AVIATION...Valid through 21/12Z.
SKC through 20/18Z, then BKN clouds 10-14k ft AGL developing from
KTUS/KOLS eastward. Convergence along a surface boundary will
likely lead to isolated to scattered -SHRA/-TSRA starting around
21/21Z through about 22/03Z. Main terminals affected will be KTUS
and KOLS. Storms will be capable of winds 35-45 kts with a 10-30
percent chance for winds in excess of 50 kts. Outside of storms SFC
winds become SELY at 15-25 kts with gusts to 30-40 kts across
much of the forecast area. The strongest winds are expected at
KDUG and KSAD terminals. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Temperatures are expected to peak today from
Tucson westward, then more seasonable temperatures thereafter.
Starting this morning, surface winds turn to the east to
southeast and become stronger, especially across
Graham/Greenlee/Cochise Counties where sustained 20-ft winds of 20
to 35 mph are expected with stronger gusts. The strongest of
these winds will be in the Upper Gila River Valley near Safford as
well as near Douglas along the International and NM borders. With
these east to southeast winds, there will be increased moisture
with min RH values in these locales around 20 percent Thursday. So
while the winds are at critical levels, RH values will remain
just above critical levels but certainly still elevated fire
weather conditions due to the strong winds and dry fuels Thursday.
Breezy to windy conditions continue Friday, though increased
moisture will have overspread more of the forecast area. A mixture
of dry/wet isolated to scattered are expected starting Thursday
afternoon from Tucson eastward and then to include the remainder
of southeast Arizona Friday. As moisture remains this weekend,
isolated to scattered thunderstorms will continue each day through
the weekend into early next week with a low to mid grade monsoon
pattern in place.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning from 10 AM this morning to 8 PM MST this
evening for AZZ501>506.

Blowing Dust Advisory from 3 PM this afternoon to 8 PM MST this
evening for AZZ502-504>506.

Wind Advisory from 5 AM early this morning to 5 AM MST Friday
for AZZ508-509.

&&

$$

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