Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 221037

Area Forecast Discussion
National Weather Service Tucson AZ
336 AM MST Wed Jan 22 2020

.SYNOPSIS...Isolated showers and patchy fog this morning will end by
midday with below normal afternoon temperatures. Dry conditions
return Thursday as temperatures warm back up to seasonable levels
and continue through the upcoming weekend. A disturbance could bring
rain chances and cooler temperatures back to southeast Arizona early
next week.


.DISCUSSION...A weak trough moving through the region this
morning continues to produces a few light showers mainly from the
Tucson area eastward. With a rather moist airmass in place, cloud
bases are particularly low with visibility periodically bouncing
between 3 SM and 6 SM in BR at KTUS and other area airports. Please
see the aviation section below for additional information regarding
the terminals. At this time, recent trends in surface observations
do not suggest great enough coverage of fog/low enough visibilities
to justify a headline, so the current forecast just mentions patchy
fog in the weather grids. In general, any fog this morning should
generally dissipate by late this morning or midday, and cloud bases
should follow suit by lifting and decreasing in coverage into this
afternoon as the shortwave moves east.

This trough will slide east into Thursday, with northwest flow aloft
and ridging building over the western third of the country into
Friday. Upper level flow will then split on the backside of the
ridge as it pushes east on Friday. This results in a shortwave
trough passing well north of our area Friday and another passing to
our south through Saturday. This pattern will ultimately have little
to no impact on our sensible weather, with temperatures Thursday
through the weekend remaining several degrees above late January

Progressive pattern continues early next week as the ridge breaks
down and a stronger system moves southeast through the PAC NW and
the Great Basin. This trough could potentially make its way toward
our area for another shot at precipitation next Monday into Tuesday.
Still too early to start talking exact timing and QFPs, but
temperatures look like they will fall to near or slightly below
normal levels once again.


.AVIATION...Valid through 23/12Z.
Isolated -SHRA from KTUS eastward this morning generally ending by
midday. Cloud bases around 5-8k ft MSL at all terminals with
visibility occasionally down to 3SM in BR or VCFG. Visibility
concerns generally ending after 22/17Z along with gradually
increasing CIGS. FEW-SCT clouds 7-10k ft MSL this afternoon with SCT-
BKN clouds above 15k ft MSL, follow by mostly clear conditions this
evening into Thursday morning. SFC winds remain variable in
direction and less than 12 kts through the period. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Isolated light showers this morning will clear and
end from west to east by midday. Dry conditions then prevail through
this weekend before another weather system may bring a chance of
valley rain and mountain snow back to the region. 20-ft winds remain
less under 15 mph through Sunday, with stronger west or northwest
breezes possible next Monday and Tuesday.





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