Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 221334

Area Forecast Discussion
National Weather Service Tucson AZ
325 AM MST Sun Apr 21 2018

.SYNOPSIS...Expect dry conditions across much of the area and
unseasonably warm daytime temperatures this week. The exceptions are
a few light showers possible southeast of Tucson this afternoon, and
a few afternoon thunderstorms mainly across the White Mountains
Wednesday through Saturday.


.DISCUSSION...Weak upper low was centered over northern Baja
California early this morning. This system will become an open wave
later this morning and move eastward across the area this afternoon
and evening. There appears to be just enough moisture associated
with this system to justify the continuation of a slight chance of
showers this afternoon and evening across far southeast sections.
Any measurable rainfall particularly favoring the Chiricahua
Mountains in eastern Cochise County should just be a few hundredths
of an inch.

Upper ridging will support clear skies to mostly clear skies late
tonight into Monday. The next broad area of low pressure aloft will
approach from the southwest Monday night, and more mainly high-level
clouds Tuesday into Wednesday as southwesterly flow aloft prevails.
In addition to this cloudiness, lower level moisture should increase
across far eastern sections as early as Wednesday.

Although some differences continued with the GFS/ECMWF and their
respective ensembles, the synoptic pattern favors the depiction of a
slight chance of afternoon thunderstorms mainly across the White
Mountains Wednesday into Saturday. Precip-free conditions will
likely continue for much of the rest of this forecast area.

Thereafter, the deterministic GFS/ECMWF were somewhat similar with
depicting a closed upper low essentially over the Great Basin by
next Sunday. Stronger westerly to southwesterly flow aloft should
shunt moisture of consequence well east of the area. Although beyond
the scope of this forecast package, this pattern if reality would
effectively end even a slight chance of thunderstorms across far
eastern sections. Daytime temps will warm to above normal readings
starting today followed by unseasonably warm daytime temps
continuing Monday into next Saturday.


.AVIATION...Valid through 23/12Z.
Isolated -SHRA mostly near New Mexico state line into early evening.
Otherwise, FEW-SCT clouds 11k-15k ft AGL and BKN clouds above 20k ft
AGL into this afternoon then decreasing clouds this evening. Mainly
SKC by daybreak Monday. Winds variable less than 8 kts this morning,
westerly/northwesterly at 8-10 kts with some gusts up to 16 kts this
afternoon, then variable less than 8 kts tonight. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Unseasonably warm temperatures are expected this
week, with readings topping out about 10 degrees above normal for
most locales. It will remain dry in most locations, with just a
slight chance of showers in southern Cochise County this afternoon.
A few thunderstorms may also occur in the White Mountains during the
afternoon Wednesday through Saturday. Any lightning would enhance
fire initiation concerns and gusty outflows may also occur.
Otherwise, winds will generally be light and terrain driven this
week, with the usual afternoon gustiness due to strong daytime






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