Area Forecast Discussion
Issued by NWS Tucson, AZ

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624
FXUS65 KTWC 210415
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
915 PM MST Sun May 20 2018

.SYNOPSIS...Expect breezy conditions Monday afternoon with a slight
chance of thunderstorms over the White Mountains, then breezy and
slightly cooler temperatures on Tuesday. A warming trend will result
in well above normal daytime temperatures by next weekend, with highs
exceeding 100 degrees from Tucson westward into the western deserts.

&&

.DISCUSSION...IR satellite imagery depicted scattered cirriform
clouds mainly west to northeast of Tucson at this time. Meanwhile,
clear skies prevail southeast to south of Tucson. Satellite trends
as well as model moisture fields suggest that the bulk of cirriform
clouds will be mainly north of southeast Arizona the rest of
tonight. Thus, clear skies to mostly clear skies through daybreak
Monday depending upon location.

The 20/21Z SREF and 21/00Z NAM12 depict the bulk of showers/tstms
Monday to be just east of this forecast area. Have noted that the
NAM12 depicted light rainfall amounts to occur across the White
Mountains Monday morning, then precip-free conditions Monday
afternoon. At any rate, the official forecast of a slight chance of
showers/tstms Monday afternoon across the White Mountains still
appears plausible.

Gusty south to southwest winds will occur from mid/late Monday
morning into Monday evening. Wind speeds are forecast to remain
below wind advisory criteria. However, forecast wind speeds in
combination with low relative humidity has led to the issuance of a
Red Flag Warning for portions of the White Mountains. The Fire
Weather section in this product has more information.

There are no updates planned at this time. Please refer to the
additional sections for further detail.

&&

.AVIATION...Valid through 22/06Z.
Isolated -TSRA/-SHRA Monday afternoon near the southeast Arizona/
southwest New Mexico state line and especially across the White
Mountains northeast of KSAD. Otherwise, a FEW clouds above 20k ft
AGL mainly north of KTUS rest of tonight, then a FEW-SCT clouds 10k-
15k ft AGL and SCT to perhaps BKN clouds above 20k ft AGL Monday
morning into Monday evening. Surface wind late Monday morning into
Monday evening sly/swly 12-22 kts with gusts near 35 kts. Surface
wind variable in direction less than 12 kts other times. Aviation
discussion not updated for amended TAFs.

&&

.FIRE WEATHER...A Red Flag Warning is in effect from noon to 7 PM
MST Monday for the northern portions of Fire Weather Zone 153
including Northern Graham and Northern Greenlee counties. The
combination of strong and gusty south to southwest winds, low
relative humidity, and a high to very high fire danger will create
critical fire conditions.

Gusty southwest winds should also occur Tuesday afternoon, with a
few locales generally south of Tucson briefly reaching critical fire
conditions. However, at this time appears that critical fire
conditions will not be widespread nor long-lived.

There is a slight chance of thunderstorms also across the White
Mountains Monday afternoon. Otherwise, dry conditions through next
weekend. Expect only minor daily high temperature changes through
Wednesday, then warmer with well above normal temperatures
prevailing by next weekend. 20-foot winds will generally be less
than 15 mph Wednesday into next weekend, although afternoon gusts
will occur due to strong daytime heating.

&&

.PREV DISCUSSION /227 PM MST/...The next storm system to affect our
weather is currently developing over northern California and it will
continue to deepen as it slowly settles to the southeast over
southern California by Monday evening. This will tighten the
pressure gradient over the region resulting in gusty winds Monday
afternoon, especially over higher elevations. It will also draw low
to mid level moisture west across New Mexico late tonight into early
Monday bringing the potential for isolated thunderstorms very close
to our eastern border. At this time is looks as though some low
level moisture will make it into the Gila Valley as far as Safford
Monday morning then quickly mix out with daytime heating. This
scenario will kill the chance for storms in our area with the
possible exception of the White Mountains where enough moisture may
linger for a storm or two. Anything that develops will quickly move
to the northeast.

By late Tuesday the storm will weaken a bit and move northeast into
Nevada. Basically, another breezy day similar to Monday just without
the threat of moisture and high temperatures peaking 3-5 degrees
lower than today or Monday.

Wednesday into Thursday the storm quickly weakens and moves north
resulting in diminishing winds and near to or slightly warmer than
normal temperatures.

Beyond that, the heat is on. Heights and thicknesses quickly rise as
a ridge builds north across the Southwest and Rocky Mountain states
Friday into the weekend. Temperatures will respond by rising
noticeably to 8-12 degrees warmer than normal by Saturday, which
this time of year means highs 100+ degrees anywhere near or below
4000 ft in elevation. While not quite approaching record levels, it
will be a very hot holiday weekend with some locations possibly
seeing their hottest temperatures of the year thus far next weekend.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
  Red Flag Warning from noon to 7 PM MST Monday for AZZ153.

&&

$$

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