Area Forecast Discussion
Issued by NWS Tucson, AZ

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688
FXUS65 KTWC 191600
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
900 AM MST THU MAY 19 2016

.SYNOPSIS...The low pressure system over Arizona will move
slowly northeast and out of the area tonight. We will still have
enough moisture for a few thunderstorms northeast of Tucson Today.
Dry conditions with temperatures recovering to near normal for the
latter part of the week. Another upper level system will impact the
region this weekend into early next week with another round of windy
conditions.

&&

.DISCUSSION...
Low pressure is evident on water vapor imagery across New Mexico and
Colorado this morning, with weak northwesterly flow in place across
Arizona. 12z KTUS sounding reveals approximately 0.75 inches of
precipitable water across the area and this is close to the values
seen in blended TPW and CIRA LPW imagery. Unlike this time
yesterday, cu buildups to the east are virtually non-existent and
mostly clear/clear skies prevail across the area. Mid morning
temperatures were generally in the mid 70s as of 16z.

Most of the precipitable water in the atmosphere is confined to the
700-500mb level...CIRA LPW suggest a very dry atmosphere above and
below these levels. There is an outside chance that one final
shortwave trough associated with the main upper low will trigger
some showers and storms this afternoon but the areal coverage should
be minimal, not to mention confined to areas well north and east of
Tucson. HRRR model is indicating some isolated late-day showers in
this area but no QPF, this is certainly plausible given dry low
levels. The inherited PoPs in the 30-40 range across northern Graham
and Greenlee Co`s seems more than reasonable and will only be
adjusted slightly based on incoming 12z model data. Overall the
forecast is in great shape with no major changes forthcoming.

&&

.AVIATION...VALID THRU 20/12Z.
Mostly clear skies early this morning with the exception of some
lingering clouds near the New Mexico border. Otherwise, scattered
clouds will redevelop at 8-10k ft agl across most of the area this
afternoon. Enough lingering moisture for a few showers and
thunderstorms, mostly across the White Mountains well northeast of
KTUS. Normal diurnal wind trends through the forecast period with
some gusts in the afternoon. Aviation discussion not updated for TAF
ammendments.

&&

.FIRE WEATHER...Enough lingering moisture for another chance of
afternoon showers and thunderstorms mainly near the White Mountains
today. Otherwise, dry conditions will prevail area-wide Friday
through early next week.

A few afternoon gusts this afternoon due to daytime heating,
otherwise fairly light winds. Breezy to locally windy conditions
will return Friday and continue through this weekend into early next
week as a low pressure system deepens northwest of the area. Wind
speeds will approach critical levels for portions of the area
generally from Tucson westward Friday and Saturday, then shifting
into eastern areas on Sunday. Breezy winds to continue Monday and
Tuesday but remaining below critical thresholds. Minimum relative
humidity values will generally be in the 10 to 15 percent range for
valley locations Friday through Sunday and 20 to 25 percent across
the mountains. Even lower minimum relative humidity values early
next week. The best potential for critical fire weather thresholds
being met will be both Friday and Saturday mainly west of Tucson
across fire weather zone 150, then for eastern areas on Sunday.
Will hold off on the issuance of any fire weather headlines at this
time given uncertainty on areal extent and borderline winds.

&&

.PREVIOUS DISCUSSION...Still looking at a chance of showers
or thunderstorms mainly in the White Mountains today. Otherwise, dry
conditions elsewhere as a ridge of high pressure aloft builds over
the region today and Friday. This will be very brief as another
storm system deepens across the western United States this weekend.
Models showed this system entering the Pacific Northwest today and
lingering over the Intermountain West over the weekend. This feature
will remain north of the area, but will result in an increase in
wind across southeast Arizona Saturday and more so Sunday. Daytime
temperatures will rebound to near normal for Friday, before lowering
a few degrees over the weekend into early next week.

&&

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

&&

$$

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