Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 190341

Area Forecast Discussion
National Weather Service Tucson AZ
841 PM MST Sun Mar 18 2018

.SYNOPSIS...Partly cloudy skies tonight with chilly temperatures
Monday morning. High pressure will bring a warming trend the first
half of the week. Another system will brush by mainly north of the
area later in the week for a few degrees of cooling, breezy winds as
the best chance of showers remains north.


.DISCUSSION...Latest WV satellite imagery shows the shortwave that
impacted our area earlier today has now pushed well to the east
across the Oklahoma and Texas Panhandle. Southeast Arizona is now
under zonal westerly flow aloft, though there is quite a bit of
cirroform cloudiness across the area and extending upstream. Even
with periods of cirrus clouds overnight, given the chilly airmass in
place, temperatures will be below normal with some normally colder
locales south and east of Tucson experiencing a freeze Monday
morning. The cool down will be short lived as temperatures begin to
moderate on Monday, though highs will still be about 3 to 6 degrees
below normal Monday afternoon. Made a few adjustments to tweak the
sky coverage overnight, otherwise forecast remains unchanged. See
previous discussion below for additional information.


.AVIATION...Valid through 20/06Z.
SCT-BKN cirrus 25k ft AGL are expected through the forecast period.
Surface winds variable in direction and less than 10 kts into Monday
morning, then becoming NW at 8-15 kts after 19/20Z before tapering
off and becoming variable Monday evening. Aviation discussion not
updated for TAF amendments.


.FIRE WEATHER...Dry conditions through Wednesday night. A few
showers may develop Thursday west of Tucson followed by a slight
chance of showers area-wide with the exception of southern Cochise
County Thursday night into early Friday. Dry conditions will return
by next weekend. Gusty west to northwest winds will continue through
the afternoon and will diminish this evening. 20-foot winds will
mainly be less than 15 mph Monday into Wednesday. Some gusty
southwest afternoon winds should return Thursday into Saturday.


.PREV DISCUSSION...The storm system that moved through northern
Arizona is now into northern New Mexico and western Colorado this
afternoon, with just a few residual light showers left behind in far
eastern portions of Arizona. Our frontal boundary has stalled out
southeast of Tucson and the remaining Arizona portion of it is in
the process of fragmenting and becoming much less distinct. Precip
was fairly limited this far south, with a lot of sprinkles and a few
light showers, but almost no locations with measurable rainfall
(including just a trace at Tucson International Airport).

A weak shortwave ridge pushing in quickly behind the trough is on
the dirty side with some mid and high cloud coming in off the
Pacific. This will moderate the potential of overnight lows in some
locations tonight, but still likely a few degrees below average for
mid March. Some areas of freezing in colder valleys east and south
of Tucson, but nothing unusual.

A stronger ridge will build in from the west over the next 48 hours,
with a rapid warming trend pushing temperatures back to 10 or more
degrees above average by Wednesday.

The pattern will consolidate somewhat later this week as a system
currently in the eastern Pacific will merge with a system digging
down the Canadian coast. We may see some leftovers shear into the
retreating ridge with some showers mainly north of our area Thursday
night and Friday. After that we`ll have to see if the pattern is
able to amplify enough to include our area as the main storm pushes
through the region. Best bet is a typical transition season storm
missing us to the north, with only gusty winds and some cooling this
far south (day 6 or 7).






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