Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 222123
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
Issued by National Weather Service Phoenix AZ
223 PM MST Tue May 22 2018

.SYNOPSIS... Dry conditions through the upcoming holiday weekend.
Gusty winds will weaken tonight and should return again this
weekend as a couple of low pressure systems move north of the
area. High temperatures will warm above seasonal normals later
this week before cooling near to slightly below normal for this
weekend.

&&

.DISCUSSION...
An upper level low is currently centered over southern Nevada this
afternoon generating clouds and thunderstorms over much of the
Great Basin. Just to the south, the Desert SW sits under dry
southwesterly flow with PWs around 0.4 inches. In response to this
low pressure system moving to our north, breezy winds have
developed this afternoon with gusts ranging from 20-30 mph across
much of our CWA. Given the dry and breezy conditions, a Red Flag
Warning remains in effect from noon to 7 PM MST today for the
White Mountains.

Models are in excellent agreement of rapidly moving this low
pressure circulation into Montana by Wednesday afternoon while
Arizona remains under weak and dry southwesterly flow. Looking
beyong this, heights will gradually build through this work week
warming temperatures a few degrees each day with upper 90s
forecast by Friday. However, this warming trend will come to a
halt on Saturday as yet another upper level low pressure system
approaches our area. Temperature gradients associated with this
approaching low will tighten surface pressure gradients  and
bring more breezes to our area come Saturday. Models agree that
modestly cooler air will also begin infiltrating our area come
Saturday and Sunday knocking high temperatures down by a few
degrees each day. Given the dry nature of this system, elevated
fire danger will also be of concern on Saturday.

Models and ensembles are in surprisingly good agreement of
lingering this upper low over our area through at least the
beginning of next week. During this period, temperatures could be
near to even slightly below normal. One caveat is that the
position of this low will really dictate our temperatures in the
extended. Previous model runs have positioned this system further
north continuing the above normal temperatures into the weekend.
However, given the latest model consensus of a more southerly
track we have trended temperatures down for the weekend as
confidence grows in this particular solution.

&&

.AVIATION...Valid through 23/18Z.
Under clear skies, gusty SSW winds will be the main aviation
concern. Gusts nearing 25-30kt will prevail through sunset, then
weaken later this evening. Directional headings this afternoon will
be somewhat more due south than is typical. The usual light and
variable drainage wind will settle in overnight. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER... A Red Flag Warning is in effect from noon to 7 PM
MST today for the northern portions of Fire Weather Zone 153; or,
more specifically for the Alpine District. The combination of
strong and gusty southwest winds, low relative humidity, and a
very high fire danger will create critical fire conditions.

Beyond this, winds will weaken Wednesday through Friday but
sustained speeds up to 15 mph will still be possible each
afternoon. Another low pressure system will approach our area this
weekend bringing another round of breezy/windy conditions on
Saturday elevating fire danger across our CWA. In general,
humidity will be very low with afternoon minimums near 10 percent
each day. Unfortunately, no precipation is expected through the
foreseeable future.

&&


.TWC WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MST this evening for AZZ153.

&&

$$


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