Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 202227

Area Forecast Discussion
National Weather Service Flagstaff AZ
327 PM MST Mon Feb 20 2017

.SYNOPSIS...Mostly dry weather and above average temperatures are
forecast through the middle of this week. Expect breezy winds by
Wednesday afternoon followed by much colder temperatures into
Thursday as a passing cold front moves through the area. There
will be a chance of showers from Wednesday into Thursday, while
additional chances for precipitation return over the weekend.


.DISCUSSION...Low clouds have been holding on over much of
northern Arizona this afternoon. The clouds over the Chinle Valley
and the eastern Coconino Plateau have thinned or dissipated, but
they persist over many other areas. Forecast soundings and short-
term hi-res models indicate that low clouds will continue to thin
or dissipate through this evening. As they do so, a few patches of
fog could briefly form while dew points remain elevated. Fog is
not expected to be extensive.

Tuesday is forecast to be the warmest day of the week as northern
Arizona is influenced by southwest flow atop a shortwave ridge
with heights peaking at the 99th climatological percentile over
southern AZ/northern Sonora. Wind speeds will increase to the
northeast of high terrain features early on Wednesday morning,
and area-wide by Wednesday afternoon as southwest flow increases
between the weakening ridge over TX and a trough over the Pacific
Northwest/northern CA. The aforementioned trough is forecast to
bring a strong cold front through northern Arizona from Wednesday
night into Thursday morning. Some light precipitation will be
possible in association with the frontal passage, with snow levels
lowering to 4500-5500 feet behind the front.

High temperatures will be around 15-20 degrees colder on Thursday
compared to Wednesday`s values, with breezy west winds. A
relatively zonal flow pattern is forecast to continue through the
early part of the weekend. Low temperatures on Friday and Saturday
morning will be near to a few degrees below average, with high
temperatures around seasonal averages.

Substantial model spread continues for the Sunday 26 Feb - Tuesday
28 Feb period. The NAEFS mean shows a weak disturbance for Sunday
with some precipitation in the ensemble average for northern
Arizona, followed by a deeper trough a couple of days later.
Confidence is fairly low for the Sunday disturbance, and somewhat
higher regarding the second feature. We will stick with a chance
of rain/snow for now.


.AVIATION...For the 00Z package...Localized BKN CIGS from 2-4kft AGL
over mainly higher terrain areas along/west of KGCN-KFLG-KPAN line
through 01-03Z, then decreasing clouds. There is a low chance of
some localized lower CIGS or fog with IFR/LIFR redeveloping 05Z-15Z
for elevations above 6500 feet MSL. VFR conditions will prevail
Tuesday, with a slight chance of -SHRA from KGCN northwest after
20Z, but probability too low to include in KGCN TAF. Aviation
discussion not updated for TAF amendments.






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