Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 181555
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
855 AM MST Thu May 18 2017

.SYNOPSIS...There is a slight chance of showers and thunderstorms
across the White Mountains today. Otherwise, dry conditions will
prevail into next week. Below normal daytime temperatures will
continue through Friday followed by much warmer temperatures early
next week.

&&

.DISCUSSION...A broadly cyclonic upper flow continues this morning
over the western and central CONUS, with a 551 dm low analyzed via
the 18/12Z upper plots to be over northeast Utah. The upper low will
move southeastward into northeast New Mexico by midday Friday. The
bulk of precipitation associated with this system will remain north
of this forecast area. Thus, precip chances via an updated forecast
will be reduced to the slight-chance category for the White
Mountains through this afternoon.

A dry northwesterly flow aloft regime will occur Friday as high
pressure aloft amplifies near the West Coast. The 18/06Z GFS and
18/00Z ECMWF/CMC then depict fairly light westerly flow aloft to
prevail this weekend as a Rex Block becomes established over the
eastern Pacific. Thereafter, these deterministic solutions were in
good agreement with depicting an amplifying upper ridge over the
area Monday into Tuesday.

Have noted that the 18/06Z GFS continued with previous GFS solutions
in depicting light rain amounts that may potentially occur near the
New Mexico border Monday. However, the ECMWF/CMC continue to not
support this scenario, with their respective measurable accum precip
fields much farther east. Believe the GFS has a bias too far west
(relative to New Mexico) with accum precip this time of year, and
this solution is again discounted. Thus, will remove the depiction/
mention of showers/tstms near the New Mexico border with the updated
forecast.

Daytime temperatures today and Friday will be about 6-10 degrees. A
pronounced warming trend is on tap this weekend followed by no
significant change in daytime temperatures Monday into next
Wednesday.

&&

.AVIATION...Valid thru 19/18Z.
Expect isolated -TSRA/-SHRA northeast of KSAD into this afternoon.
Otherwise, FEW-SCT clouds around 8k-12k ft AGL KTUS vicinity
eastward into this evening followed by clear skies late tonight into
Friday morning. Surface wind this afternoon and early this evening
wly/nwly 10-22 kts with gusts to near 30 kts. The highest speeds
will be east of KTUS. Surface wind variable in direction less than
12 kts at other times. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...There is a slight chance of showers and
thunderstorms across the White Mountains today. Otherwise, dry
conditions will prevail into next week. Below normal daytime
temperatures will continue into Friday, then much warmer
temperatures will occur by early next week. 20-foot winds will be
west to northwest with gusts to 25 mph this. Less wind will
generally occur Friday into early next week, although afternoon
gusts will prevail due to strong daytime heating.

&&

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

&&

$$

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