Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 231603

Area Forecast Discussion
National Weather Service Tucson AZ
903 AM MST Thu Feb 23 2017

.SYNOPSIS...Dry conditions will prevail through Saturday. A cold
frontal passage will usher in much cooler temperatures today and
Friday. A brief warmup on Saturday before a fast moving system
pushes across the area on Sunday. A stronger Pacific storm will
bring a chance of valley rain and mountain snow to the area on
Monday and Tuesday along with below normal temperatures.


Mid morning WV imagery reveals a series of upper lows to our north
and west, with one area over Utah/Colorado/Wyoming and another off
the Pac NW coast. A weak trough moved through the area Wednesday
evening and had shifted into the central plains overnight, leaving a
broad area of northwesterly/zonal flow across Arizona. The trough
also ushered in drier air to the area with dewpoints generally in
the teens and 20`s along with somewhat cooler temperatures. Mid
morning readings across the area as of 16Z were generally in the
low/mid 50s under sunny skies.

The forecast for the rest of the day looks in great shape and won`t
require any major updates. Expect winds to increase this afternoon
with west winds around 15-20mph common in/around Tucson. Higher wind
speeds are anticipated in the higher terrain east of town along the
AZ/NM border but nothing strong enough to warrant any wind
advisories. Aside from the breeziness, the main story will be cooler
than normal temperatures with highs only forecast to reach the mid
60s. Similar temps are forecast tomorrow with a slight increase back
to normal by Saturday.


.AVIATION...Valid through 24/12Z.
Clear to scattered clouds above 15 kft through the period. Surface
wind generally less than 10 kts, except west to northwest 12 to 22
kts with gusts to 30 kts between 23/18Z to 24/06Z. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...A weather system passing by to the north of the area
will bring cooler temperatures today and Friday. Dry air and gusty
winds associated with the passing system will result in near
critical fire weather conditions in Cochise county today. Otherwise,
wind speeds will not be strong enough elsewhere to be of a concern.
A brief warmup can be expected on Saturday before another system
passes through the region on Sunday. A stronger Pacific storm will
bring a chance of valley rain and mountain snow to the area on
Monday and Tuesday along with below normal temperatures.


.PREVIOUS DISCUSSION...Latest WV/IR satellite imagery shows a band
of mid-high clouds associated with a trough pushing east across
Cochise County, with clear skies elsewhere. Meanwhile, at the
surface, a cold front is rapidly marching eastward across the
forecast area. This will usher in much cooler temperatures today
with highs topping out 10 to 15 degrees colder than Wednesday.
Meanwhile, the pressure gradient will remain enhanced enough to
result in a few enhanced breezes this afternoon mainly near the New
Mexico border. Dry weather continues Friday under west to northwest
flow aloft with continued below normal temperatures.

The dry weather will continue into this weekend under continued
westerly flow aloft with temperatures returning to near seasonal
normals on Saturday. There remains some uncertainty heading into
Sunday as a shortwave trough is progged to move through the flow.
The 00Z GFS is the most aggressive with this solution as it depicts
a fairly potent trough across the northern half of the state.
Meanwhile, the 00Z ECMWF/CMC and ensembles depict a much weaker
system. We have gone ahead and leaned towards the weaker solution
but confidence is below average for this time frame. This weaker
solution would keep most of southeast Arizona dry except for the
White Mountains where a few showers are possible. Meanwhile,
temperatures on Sunday will be a bit cooler than anticipated earlier
with highs about 5 degrees below normal.

A more amplified trough with additional moisture is still expected
to impact the region Monday into Tuesday. The bulk of the shower
activity should remain to the north and west of Tucson during the
day Monday, with the highest PoPs Monday night into Tuesday across
the forecast area. Otherwise, expect continued below normal
temperatures early next week with some breezes as well. Dry weather
should return by Wednesday.






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