Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
843 AM MST Sun Oct 7 2018

.SYNOPSIS...Scattered to numerous showers with embedded
thunderstorms are expected today and Monday. Much cooler
temperatures and gusty winds will also occur, especially today.
Expect drier conditions with a warming trend Tuesday into Wednesday
before another chance of showers occurs next Thursday into Friday.

&&

.DISCUSSION...A cold front is slowly pushing east across the state
and currently extends from Snowflake AZ, SW just east of Phoenix to
near Ajo. Showers and thunderstorms have been developing along and in
advance of this front all night with convection just to our north at
this time. This feature and the associated upper trough will be our
weather players for the day.

The morning sounding was rather anemic and if that were to be the
air mass for the day it would be quiet. However, cooling aloft as the
trough shifts east will provide for a much more unstable atmosphere
this afternoon which is readily apparent in model soundings. That
along with upper level divergence coupled with low level convergence
should result in showers and thunderstorms developing over a good
part of SE AZ late this morning into the evening hours. Each of the
various convective allowing models that I have looked at have some
variation of that theme with storms developing along and in advance
of the approaching cold front late this morning (which would be areas
generally east of a Casa Grande/Sells line. As we get into the later
afternoon into the evening hours convection is possible pretty much
anywhere as several lines are likely with the primary lines being
near the cold front over Cochise county at that time and the upper
trough axis which will be over western Pima county. Some potential
for strong thunderstorms today and that will need to be monitored
with flash flooding also a somewhat lesser threat. Heavier showers
will likely bring the snow level briefly down to the higher peaks of
the sky islands this afternoon as well including the Summerhaven
area.

As we slide into Monday the deep upper trough axis is sitting over
the area which will result in a cool day with scattered showers
developing in the afternoon. The dynamics will be east of the area
so the convection will be weaker and random in nature with fairly low
snow levels pushing near or a bit below 8000 feet. It will likely be
the coolest day of the week with many higher elevation valleys
remaining in the 60s and the lower deserts struggling to reach the
mid 70s.

Tuesday into Wednesday we will be on the back side of the upper
trough with drier conditions with warming but still cooler than
normal temperatures. This period is just the calm before the storm?

Models continue to indicate that the area will be impacted by the
remnants of Sergio in some form or fashion in this complex large
scale pattern that is evolving. Last nights solutions handled the
interaction between the tropical system and the westerlies in a very
different manner than the previous runs. Under the current scenario
we would still end up with rainfall, however the intensity would be
reduced. We are still five days out with a complicated situation
that models have historically had a problem resolving at longer time
ranges so we will continue to monitor and adjust as needed.

&&

.AVIATION...Valid through 08/18Z.
Scattered to numerous SHRA with embedded TSRA developing this
morning and continuing thru Monday morning. Otherwise, SCT-BKN cloud
decks lowering to 6k-10k ft AGL, with potential MVFR conditions near
the mountains and TSRA. SFC wind increasing and becoming swly at
10-25 kts with gusts to near 35 kts into the afternoon. Aft 07/21Z,
SFC wind becoming wly and slowly diminishing during the mid to late
evening hours tonight. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...There is a chance of showers and thunderstorms
through Monday. A few showers may continue Tuesday across the White
Mountains followed by dry conditions area-wide Wednesday. A chance
of showers returns to much of the area Thursday into Friday. Expect
gusty winds today, with terrain driven 20-foot winds generally less
than 15 mph through much of the upcoming week.

&&

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

PUBLIC...Cerniglia
AVIATION....Zell
FIRE WEATHER...Zell

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Special Weather Statement
National Weather Service Tucson AZ
106 PM MST SUN OCT 7 2018

AZZ502-504-505-072045-
Tohono O'odham Nation including Sells-Tucson Metro Area including
Tucson/Green Valley/Marana/Vail-South Central Pinal County including
Eloy/Picacho Peak State Park-
106 PM MST SUN OCT 7 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN PIMA AND SOUTH
CENTRAL PINAL COUNTIES UNTIL 145 PM MST...

At 105 PM MST, Doppler radar was tracking a strong thunderstorm 19
miles south of Arizona City, or 28 miles south of Casa Grande, moving
east at 25 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Avra Valley and Friendly Corners.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3236 11175 3254 11180 3266 11143 3241 11134
TIME...MOT...LOC 2005Z 254DEG 20KT 3247 11169

Cerniglia