Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 302140
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
240 PM MST MON MAY 30 2016

.SYNOPSIS...A weak and slow moving upper level low will maintain
temperatures below average through Wednesday. As this low passes
overhead Tuesday into Wednesday there will be a slight chance of
afternoon showers and thunderstorms to the area. Strong high
pressure will then build over the region late in the week into next
weekend, resulting in much hotter daytime temperatures with highs in
the triple digits for most of the lower elevations of southeast
Arizona. Highs around 110 degrees possible west of Tucson this
weekend.

&&

.DISCUSSION...May has been an enjoyable month but later this week
it will be a distant memory as summer arrives with gusto. More on
this later in the discussion.

For today, we`ve seen a nice push of moisture across the area in the
past 24 hours with precipitable water values in 0.30" to 0.50"
range. The surface dewpoints that were in the upper 40s and to lower
50s this morning east of Tucson have mixed out into the upper 30s to
mid 40s. Visible imagery this afternoon showed extensive cumulus
field east of a Globe-Tucson-Nogales line with radar depicting
isolated storms. Storms were more scattered east of the border
across SW New Mexico. Will maintain low end PoPs east of Tucson with
any storm capable of producing gusty/dusty outflows.

All of today`s activity being driven by an upper level low that was
situated between Phoenix and Lake Havasu City this afternoon. Models
are similar in dropping this upper low SSE over western Pima county
after midnight, then over northwest Sonora Mexico by late Tuesday
morning and then into northwest Chihuahua Mexico on Wednesday. Will
maintain low end PoPs mainly over the mountain with better chances
up in the White mountains. Interesting to see if the models are
correct with some overnight, Tues night into Wed morning, light
showers on back side of low from Tucson west. The below normal high
temperatures that have been the norm for the past week plus will
close out May and start June.

After a second consecutive below normal May, the first full weekend
of meteorological summer with be a rather hot one with record high
temperatures possible as strong high pressure builds over the desert
SW. Based on 12z GFS/ECMWF 850-700 mb thickness values, I went ahead
and upped highs a few degrees Friday thru Sunday. However still may
not be hot enough in spots. May eventually need to an excessive heat
watch for areas from Tucson west this weekend. As the week
progresses these highs will continue to be updated. I went back to
last June when the lower deserts had highs in the 109-113 range
around mid-month. The upper ridge later this weekend will be much
more amplified over the western CONUS versus a year ago. Hello
summer.

&&

.AVIATION...VALID THRU 01/00Z.
Mostly clear skies except for sct-bkn cumulus clouds around 8-10k ft
AGL east of KTUS with isold -tsra east of Wilcox thru 31/02z.
Surface wind sly/swly at 12-18 kts with gusts to 25 kts then become
light and variable aft 31/03z.  Lighter swly wind 8-12 kts
developing after 31/18z. Aviation discussion not updated for TAF
ammendments.

&&

.FIRE WEATHER...Widely scattered convection will quickly diminish
late today with skies becoming clear overnight.  Until then there is
a small chance for a lightning strike and local gusty outflow
winds east of Wilcox. A slight chance of thunderstorms also exists
Tuesday for western and northern areas, and Wednesday for eastern
areas.  Also, Haines 6 conditions are likely each afternoon through
Wednesday across zone 153 and much of zone 152.

Thursday onward a large upper ridge will build over the region
resulting in very hot temperatures, low relative humidities and
generally light winds through next Monday. As a result of the hot
and dry air mass, unstable Haines 6 conditions will develop across
much of southern Arizona from Friday onward through Monday. Cerniglia

&&

.TWC Watches/Warnings/Advisories...None.

&&

$$

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