Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 191645

Area Forecast Discussion
National Weather Service Tucson AZ
945 AM MST Thu Jan 19 2017

.SYNOPSIS...A series of storms will spread valley rain, mountain
snow and gusty winds over Arizona this evening into Saturday. Snow
levels will lower through that time potentially reaching the valley
floors east of Tucson by Saturday. After a break in the weather on
Sunday, another storm system is likely on Monday and Tuesday.


.DISCUSSION...Mostly cloudy conditions across SE AZ this morning per
latest satellite imagery with radar depicting virga to very light
shower activity west of Tucson. Morning upper air plots places short
wave ridge axis along AZ/NM border while to the west there was an
upper level trof extending from e-central CA to sern CA. For today
the best chances for isolated showers will be west and north of
Tucson while daytime highs will be cooler than normal thanks to the
cloud cover.

Upper dynamics increases over the area later tonight with scattered
showers this evening increasing in areal coverage during the
overnight hours. Decent upslope flow will bring enhanced snowfall
rates this evening across the northern mountain ranges which
includes the Catalinas, Rincons, Pinalenos and up to the White
Mountains. Winter storm warning goes into effect later this evening
for these ranges with snow amounts on the low end of warning

Main event with stronger/colder/wetter upper level trof still on
track for Friday afternoon into Saturday morning. More on this in
afternoon package once all 12z model data has been looked at.


.AVIATION...Valid through 20/18Z.
BKN-SCT 9-12k ft AGL with isold -SHRA, especially W and N of KTUS.
Cloud bases lowering as the day progresses, with SCT-BKN 6-10k ft
AGL after 19/21Z into this evening. As a weather system moves in
tonight, MVFR conditions are possible as -SHRA coverage increases
along with BKN-OVC clouds at 3-6k ft agl mainly after 20/06Z.
Surface winds will exhibit typical diurnal trends and generally be
less than 10 kts this morning, then increasing from the southwest
after 19/20z. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...A series of storms will spread widespread
precipitation across the area this evening into Saturday. Gusty west
to southwest winds are expected at times through this period
especially Friday night and across the mountains. Dry weather
returns Sunday before another storm affects the area Monday into


 Winter Storm Warning from 8 PM this evening til noon MST Saturday
  for AZZ510-511-514.

 Winter Storm Warning from 5 PM Friday til noon MST Saturday for



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