Area Forecast Discussion
Issued by NWS Tucson, AZ

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256
FXUS65 KTWC 221552
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
852 AM MST Sun Apr 22 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 near some eastern mountains the
second half of the week.

&&

.DISCUSSION...The weak low we`ve been looking at from the eastern
Pacific is now opening up as it moves into the northern Gulf of
California and northern Mexico near the border. Mid level moisture
with some ACCAS and virga / light showers in southern Cochise
county this morning. HRRR trends are up for the afternoon over
there, and considering current analysis we pushed PoP chances up
SE of Tucson. With heating, I wouldn`t be surprised if we saw a
lightning strike or two near the Chiricahua mountains this
afternoon.

Otherwise, steady as she goes with the warming trend into early
this week and enough mid level moisture with weak disturbances
embedded in the flow to bring a few thunderstorms to the eastern
mountains later in the week. Please see the previous discussion
below for additional details.

&&

.AVIATION...Valid through 23/18Z.
Isolated -SHRA mostly near New Mexico state line into early
evening. Otherwise, SCT clouds 10k-15k ft AGL and BKN clouds
above 20k ft AGL into this afternoon then decreasing clouds this
evening. Mainly SKC by daybreak Monday. Normal wind trends
generally less than 10 kts. 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
few light showers in southern Cochise County this afternoon. A
few thunderstorms may also occur near eastern 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 heating.

&&

.PREV DISCUSSION...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.

&&

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

&&

$$

Meyer/Francis

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