Excessive Heat Warning 5, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
307 PM MST Mon Jun 1 2020

.SYNOPSIS...Temperatures remaining hotter than average most of
the week, with afternoon highs peaking again on Wednesday and
Thursday. We'll maintain enough moisture for showers and
thunderstorms especially this afternoon and evening, and again
Friday. A little drier with spottier chances otherwise.

&&

.DISCUSSION...A little less moisture this afternoon with even
weaker shear. Storms are showing less organization as a result
with some drying infiltrating in eastern areas. Once again expect
a strong diurnal trend with not much to talk about after 03Z.

As mentioned yesterday, the easterly impulse from northern Mexico
has lifted into west Texas and will fill a bit over the next 36
hours. The low off the northern Baja coast is losing most of it's
higher latitude support, so it should be satisfied right where
it's at over the next 72 hours or so. That gives plenty of room
for the high to amplify and reconsolidate nearly overhead once
again by mid week. Near record high temperatures with excessive
heat concerns Wednesday and especially Thursday. The moisture
field will weaken with little to no flow and strong subsidence
will limit additional convection.

A kicker system digging down from the Gulf of Alaska should push
the low off northern Baja back into play to end the week.
Ensembles and ensemble means tend to shear it into the front flank
of the new mean trough position across most of the west. A little
shear and a little upstream moisture as this happens should bring
a few thunderstorms back into the picture Friday (or Saturday if
this evolves a little slower than expected...as it often does in
these situations).

A quick look at ECMWF weeklies suggest height anomalies that would
continue to support a favorable early season monsoon pattern from
mid to late June. Western Mexico is still getting its act
together, so it would likely be relatively low grade monsoon
activity with that.

&&

.AVIATION...Valid through 03/00Z.
Isolated to scattered -TSRA/-SHRA thru 02/04z favoring an area from
Nogales to Kitt Peak to Oracle to KDUG, and in the White Mountains
northeast of KSAD. Otherwise, SKC-FEW clouds above 15k ft MSL west
of Kitt Peak, with SCT-BKN clouds at 10k-14k ft MSL from Kitt Peak
eastward. Brief wind gusts to 40 kts may occur due to TSRA outflows.
Outside of any TSRA outflows, SFC wind generally 12 kts or less and
variable in direction, with some gusts around 20 kts thru the early
evening hours due to strong surface heating. Isolated -TSRA/-SHRA
developing again aft 02/18Z, mainly along the International Border
between KOLS and KFHU and in the White Mountains. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Isolated to scattered afternoon and evening
thunderstorms are expected today, favoring an area from Oracle
southwest to Sells and southeast to Douglas, as well as in the White
Mountains. Storm chances decrease on Tuesday to mainly along the
International Border from Nogales to Sierra Vista and in the White
Mountains. The drying trend continues Wednesday and Thursday with
any storms limited to the White Mountains. Another uptick in
thunderstorm activity occurs on Friday, mainly northeast of Tucson.
Dry conditions are expected areawide this weekend through early next
week.

Gusty and erratic winds will occur at times due to thunderstorms
outflows, and potential fire starts due to lightning. Expect breezy
southwest 20-foot winds on Friday at 15-20 mph. Elevated 20-foot
winds continue across eastern areas this weekend. Otherwise, 20-foot
winds will mainly remain under 15 mph, with occasional afternoon
gusts due to strong surface heating.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Watch from Wednesday afternoon through Thursday
evening for AZZ501>507-509.

&&

Public...Meyer
Aviation...Zell
Fire Weather....Zell

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