Special Weather Statement, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
840 AM MST Fri Jun 28 2019

.SYNOPSIS...High pressure will bring hotter temperatures the next
few days. A moisture increase from the south will bring a few
afternoon thunderstorms around the area as well, accompanied by
strong gusty outflow winds.

&&

.DISCUSSION...
Morning radar and satellite imagery revealed a few showers across
the area around daybreak, associated with lingering moisture from
Thursday evening convection over Cochise County and parts of New
Mexico. They have since dissipated as of 15Z with only some
lingering mid clouds in place. Taking a look at dewpoints across the
area, readings are generally in the mid to upper 40s east of Tucson
and considerably drier to the west. Morning sounding from KTUS
revealed around 0.95 inches of precipitable water which has since
risen to around 1.1 inches per satellite derived estimates. Some of
this is shallow in nature and some degree of mixing is still
expected later today.

Two areas of focus today...heat...and storms. Despite the early
cloud cover and increased moisture, today will be one of the hottest
days of the year so far with highs in the 105-108 range in Tucson
with similar values around Safford. This will result in moderate
risks of heat related illness. Similar, but slightly lower
temperatures, are expected through the weekend. In terms of
convection, latest HREF and HRRR runs indicate convection blossoming
along the AZ/NM border around 19Z with even a few storms firing up
closer to Tucson. Instability parameters drop off considerably the
farther west one goes, same story with moisture. In all likelihood,
areas east of Tucson will see showers and thunderstorms with gusty
winds, lightning, and brief heavy rain. In Tucson itself, convection
will likely be dependent on colliding outflows and even then,
anything that develops should be short lived with light rain. Gusty
winds/lightning will be the main story in Tucson today. Areas west
of town should see little to nothing in terms of storms as the
atmosphere is too unfavorable to sustain convection.

&&

.PREV DISCUSSION...Strong high pressure is anchored over New Mexico
and Chihuahua this morning. A southerly mid level flow around the
high is trying to import a little more moisture. 1 inch values are
just south of the border with HRRR and HREF ensembles suggesting
values between 1 and 1.1 inches pushing into Santa Cruz, and eastern
Pima counties later today. Outflow from New Mexico is pushing
similar values into Greenlee, Graham and Cochise counties. We'll
actually have some debris could from earlier Sonoran storms this
morning, but by late morning expect solid insolation with
temperatures a couple of degrees hotter this afternoon. With better
convective potential it looks like a good early monsoon day favoring
tight tall storms over mountains by 2 PM with a few outflows into
valleys. Dry microburst activity as storms push off the mountains
but I wouldn't rule out a couple of valley storms by late afternoon
and early evening.

The orientation of the ridge along with the high center
reconsolidating a little further north over the next 48 hours
should keep enough moisture around for low grade monsoon activity
the next few days. Tropical Storm Alvin is heading into much cooler
waters west of southern Baja. As it moves into a position to
engage with the higher latitude flow, expect the sheared remains
to not hold together well at all, even at mid levels. Trajectories
suggest a path between our ridge and the trough near the west
coast. That means it stays northwest of our area.

The larger scale position of the high doesn't look the best next
week, but we may see an upturn closer to more solid thunderstorm
days with an inverted trough leading to a strong and organized
increase in thunderstorms through Sonora. This will increase our
chances of stronger and deeper direct outflow and gulf surge
activity.

&&

.AVIATION...Valid through 29/18Z.
Cloud cover increasing through the day with SCT-BKN decks generally
from KTUS eastward and isol'd to sct -TSRA/-SHRA developing this
afternoon, particularly near terrain. Confidence is not high enough
that -TSRA/-SHRA will impact terminals to be included in TAFs. SFC
wind ELY/SELY this morning at less than 10 kts becoming SWLY to NWLY
at 10-14 kts this afternoon. -TSRA could produce outflow winds
gusting up to 35 kts at times. Winds calming and following terrain
tonight into Saturday morning. Aviation discussion not updated for
TAF amendments.

&&

.FIRE WEATHER...Increasing moisture into next week will bring shower
and thunderstorm chances to the region each afternoon, particularly
east of Tucson to the NM border. Dry lightning will continue to be a
concern, with the best chance for wetting rain occurring in the
highest elevations. Gusty and erratic outflow winds are also
possible with any storms, with speeds nearing 40 mph at the 20-ft
level. Otherwise, 20-ft winds are expected to remain less than 15
mph through at least Monday. Daytime humidity minimums will dip to
10-15 percent through Sunday, with a very gradual increase in these
minimums occuring next week. High temperatures through Monday are
expected to be a few degrees above normal before dropping to near
normal by the middle of next week.

&&

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

&&

Leins/Meyer/Carpenter

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Special Weather Statement
National Weather Service Tucson AZ
1221 PM MST Fri Jun 28 2019

AZZ507-513-282015-
Upper San Pedro River Valley including Sierra
Vista/Benson-Dragoon/Mule/Huachuca and Santa Rita Mountains including
Bisbee/Canelo Hills/Madera Canyon-
1221 PM MST Fri Jun 28 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN COCHISE COUNTY UNTIL
115 PM MST...

At 1221 PM MST, Doppler radar was tracking a strong thunderstorm over
Sierra Vista, moving north at 15 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Sierra Vista, Hereford, Whetstone, Huachuca City, Fort Huachuca,
Fairbank, Charleston and Ramsey Canyon Preserve.

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 3142 11019 3146 11043 3172 11045 3174 11013
TIME...MOT...LOC 1921Z 187DEG 11KT 3153 11032

LEINS