Area Forecast Discussion
Issued by NWS Tucson, AZ

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS65 KTWC 181614

Area Forecast Discussion
National Weather Service Tucson AZ
914 AM MST Sat Feb 18 2017

.SYNOPSIS...A strong Pacific storm system will bring some valley
rain, mountain snow and cooler temperatures this weekend. Expect
gusty winds into today before winds diminish Sunday. Dry
conditions with a strong warming trend will then prevail Monday
into the middle of next week. Cooler temperatures will occur next
Thursday and Friday with dry conditions continuing.


.DISCUSSION...Deep storm system now coming onto the west coast
with broad area of rain just west of the area. There is a narrow
band of showers bisecting the area NW-SE with isolated light
showers south of Casa Grande to Nogales and more numerous and
heavier showers to the north. Looking at satellite and radar
trends as well as the latest meso-scale models leads me to feel
this situation will continue to play out much of the day until the
storm draws close enough to enhance the precipitation with
stronger dynamics primarily this evening onward. This is
especially true for the immediate Tucson area which under this
flow regime frequently gets downsloped resulting in a donut-hole
effect. With this I trimmed pops a bit this afternoon locally and
tweaked temps a bit with the update already having been sent. The
idea was to focus the attention to this evening onward. Other than
that have not made significant changes at this time.


.AVIATION...Valid through 19/12Z.
ISOLD-SCT -SHRA mainly west of KTUS, then numerous valley -SHRA
and higher terrain SHSN by later today into tonight. ISOLD -TSRA
may also occur this afternoon, mainly from KTUS south and west.
MVFR and occasional IFR conditions are expected particularly near
the mountains. Otherwise, cloud decks will be at 4k-8k ft AGL.
Surface wind sely/sly 18-26 kts with gusts to near 40 kts between
18/15Z-19/00Z, then diminishing tonight. Aviation discussion not
updated for TAF amendments.


.FIRE WEATHER...A strong Pacific storm system will bring widespread
valley rain and mountain snow this weekend. Gusty southeast/south 20-
foot winds will occur today, with the winds diminishing tonight, but
remaining on the breezy/gusty side through Sunday. Dry conditions
with a strong warming trend will occur Monday into the middle of
next week.


.PREV DISCUSSION... /issued 317 AM MST Sat Feb 18 2017/

DISCUSSION...A storm system continued to move into California
early this morning with showers increasing across western and
central Arizona. Regional radars were showing an extensive band of
showers along the Colorado River with more development farther
east across central and northern portions of this state. Isolated
to scattered light showers had already moved into western and
central Pima county as of 245 AM MST. Models were still
advertising a rather wet system moving through the area today into
Sunday. Strong winds will develop this morning in advance of the
main system. A Windy Advisory has been post for portions of
southeast Arizona through 4 PM MST today. The snow level ahead of
the system was still rather high, above 8000 feet, early this
morning but will gradually lower throughout the day and tonight. A
Winter Storm Warning for above 7500 feet remains in effect from 3
PM MST today until 5 PM MST Sunday. Models showed the system
exiting the area late Sunday with improving weather from west to
east Sunday night. A ridge of high pressure aloft will build over
the region Monday into Tuesday with daytime temperatures
rebounding. Thereafter, another system was progged to track
through the Rockies brushing southern Arizona on Wednesday into
Thursday. At this time, the bulk of the precipitation chances
associated with this system will be north of the area.


Winter Storm Warning from 3 PM this afternoon to 5 PM MST Sunday
for AZZ510-511-514.

Wind Advisory until 4 PM MST this afternoon for AZZ502>504-507-

Winter Weather Advisory from 3 PM this afternoon to 5 PM MST
Sunday for AZZ512.



FIRE WEATHER...Cerniglia

Visit us on Facebook...Twitter...YouTube...and at is the U.S. government's official web portal to all federal, state and local government web resources and services.