Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 162115
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
215 PM MST Tue Jan 16 2018

.SYNOPSIS...Gusty winds will generally taper off as the afternoon
progresses, though another bout of gusty easterly winds is expected
Wednesday. Cooler temperatures will continue especially east of
Tucson on Wednesday. Otherwise, very warm mid-January afternoon
temperatures and generally dry conditions will persist through
Friday. A pattern change this weekend will bring much cooler
temperatures and the chance of valley rain and mountain snow
Saturday.

&&

.DISCUSSION...Latest IR/WV satellite imagery shows mostly sunny
skies across much of southeast Arizona, though increased cirroform
cloudiness is working into the western half of the forecast area.
Weak ridging aloft remains in place this afternoon, though
temperatures are much colder across Graham/Greenlee/Cochise Counties
with highs in the 50`s this afternoon as a backdoor cold front has
ushered in colder air into these areas. Much warmer from Tucson
westward with temperatures remaining above normal. The gusty
easterly/southeasterly winds will continue to taper off the rest of
this afternoon, though some breezes are possible again on Wednesday.

The aforementioned weak ridging aloft will break down tonight as a
weak shortwave moves across northern and eastern Arizona. This
system is quite moisture starved with a lack of lower level
moisture. However, we can`t rule out a slight chance of rain and
snow showers across the White Mountains tonight and Wednesday
morning.

Progressive shortwave ridging will move across the area Thursday
into early Friday ahead of a more significant trough poised to move
in just in time for the weekend. The ridging will result in benign
weather on Thursday with daytime temperatures continuing to warm.
Friday will start the transition with continued mild temperatures
and perhaps a few afternoon breezes.

Latest 12Z model guidance is fairly similar to previous model
guidance with the trough this weekend. 12Z ECMWF is still perhaps
about 6 hours slower than the GFS with a cold front sweeping across
the area on Saturday. This system will be rather moisture starved
given its progressive nature and trajectory. The biggest change will
be the sharply colder temperatures both Saturday and Sunday with a
freeze possible in Tucson Sunday morning. Regarding precipitation
chances, there will be a chance of a few valley rain and mountain
snow showers along with the cold front and then due to the trough
axis and instability later Saturday and into Saturday evening. QPF
amounts will be rather meager with most locales seeing less than
0.10". Snow levels could briefly get down to valley floors south and
east of Tucson Saturday evening before the moisture kicks out of
here but not expecting any impacts at this time. A few inches of
snow are possible in the mountains but this isn`t shaping up to be a
significant winter storm. A more zonal westerly flow is expected
early next week with temperatures warming up to about seasonably
normal levels on Monday and Tuesday.

&&

.AVIATION...Valid thru 17/23Z.
FEW-SCT clouds at 12k-15k ft AGL and BKN-OVC clouds AOA 20k ft AGL
thru 17/07Z. Aft 17/07Z, SCT-BKN clouds above 20k ft AGL. ELY/SELY
SFC wind at 15-20 kts with gusts to 22-27 kts. Speeds will decrease
this evening into the 10-15 kts range, continuing from an ELY/SELY
direction through the remainder of this forecast cycle. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...A storm system passing north of the area will
result in a slight chance of showers mainly in the White Mountains
tonight into Wednesday. East to southeast winds will continue
through Wednesday, but wind speeds will begin to subside this
evening. Dry conditions return on Thursday before another storm
system moves across the area starting late Friday night, persisting
into Sunday morning. This system will result in cooler temperatures,
breezy west/southwest winds and scattered valley rain and mountain
snow showers. Dry conditions and near normal high temperatures
return early next week.

&&

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

&&

$$

Discussion...GL
Aviation/Fire Weather...Zell

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