Area Forecast Discussion
Issued by NWS Flagstaff, AZ

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FXUS65 KFGZ 141610
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
910 AM MST Thu Mar 14 2024

.SYNOPSIS...A prolonged winter storm event will impact northern
Arizona through this weekend, resulting in breezy winds, colder
temperatures, and periods of rain and mountain snow. Hazardous
travel in the High Country is expected late Thursday through
late Friday, due to accumulating snowfall.

&&

.UPDATE...The 500mb low is sagging southward, now centered
somewhere near Searchlight, Nevada. A few showers are impacting
Mohave County, AZ and Clark County, NV this morning, but this is
just a taste of what is yet to come. Precipitation will develop
across the rest of Arizona only after moisture builds back into
the region, which looks to occur this afternoon into this evening.
The short term forecast was updated with the latest precipitation
trends. Stay tuned for further updates.

&&

.PREV DISCUSSION /419 AM MST/...A relatively calm night is expected
for the rest of tonight, ahead of the arrival of a closed low,
now approaching the Las Vegas area. A 100kt jet on the western
side of the low is still moving it southward tonight, some
retrograding is also occurring as a rex block forms over the
western United States.

This is a very tricky situation to forecast, for many reasons. First
and foremost, the final low position is still not agreed upon among
the deterministic models, but we seem to be converging on a position
over far southern California at some point later tonight. This is
even further southwest than was previously thought and has been the
trend. In addition, some fairly dry air has moved into the northern
half of Arizona, behind the cold front from Wednesday. Very dry air
is also being forced down the Lower Colorado River Valley, powered
by strong northerlies in the boundary layer.

What this means is, we will now have to wait longer and work harder
to get moisture advection back into Arizona from the south, but it
will happen. When the low stabilizes, a strong warm advection sector
develops on the eastern side, along with the moisture advection from
the south. This will essentially set up a south to north warm front
that will roughly set up along or east of the I-17 corridor. Bands
of rain and snow will then develop along this frontal boundary. The
eastern zones will go nearly dry, with rising snow levels as this
occurs and will have to wait until the low begins to move on Friday.

Complicating matters will be convective structures that form in the
daytime hours, due to the cold air aloft. As we saw on Wednesday
afternoon/evening, these convective features can produce a whole
bunch of snow in a hurry, aside from, or in addition to, the banded
frontal precipitation.

Further complicating matters is that the low is not only cut off
from the main flow, but it resides under a block, making movement
very difficult to forecast. In fact, once it does move, it is likely
to move back, perhaps even repeating several times,

Eventually, the the dynamics within the low will weaken and move
east, leaving us with diurnally driven convection, within a wobbling
and dancing low. There could be significant precipitation in this
pattern as well, but it will be more localized and likely in the
daytime.

Due to all these issues, we have delayed the onset of the WSW
products. Central Arizona is more likely not to develop until this
evening into Friday, while the eastern zones will wait at least
until Midnight MST. Perhaps much longer, if the low doesn`t wobble
eastward on Friday.

Once again, this is very difficult, in some ways unpredictable. What
we we can say is that multiple days of cool, wet and wintery weather
can be expected. If you are traveling, be prepared.

&&

.AVIATION...Thursday 14/12Z through Friday 15/12Z...VFR conditions
likely to persist through 18Z, with MVFR/IFR conditions increasing
afterwards. -SHRA/-SHSN will start after 18Z, mostly along and
north of a KPRC-KINW-KRQE line, and continue through the TAF
period. Periods of LIFR conditions possible within +RA/+SN. Look
for E through S winds 5-15 kts, with stronger gusts near storms.

OUTLOOK...Friday 15/12Z through Sunday 17/12Z...MVFR/IFR and
periods of LIFR will persist through much of the outlook period
due continuous rain/snow showers. Look for S-SE winds on Friday
10-15 kts, with stronger winds (15-25 kts) along our eastern
border. Lighter winds look to return over the weekend.

&&

.FIRE WEATHER...Thursday and Friday...Rain and snow showers will
continue today and tomorrow, with varying snow levels. Heaviest
precipitation likely between late Thursday into Friday. Periods of
thunder will also be possible. Look for east through south winds
today 5-15 mph, becoming southerly at 10-25 mph on Friday.

Saturday through Monday...Isolated to scattered showers remain
through Monday. Expect winds generally between 5-15 mph, with
varying directions.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 PM MST /9 PM MDT/ this evening to
5 PM MST /6 PM MDT/ Friday for AZZ004-006-007-015-016-018-038.

Winter Weather Advisory from 11 PM MST /midnight MDT/ this
evening to 11 PM MST /midnight MDT/ Friday for AZZ011-017-039.

&&

$$

PUBLIC...Benji/Peterson
AVIATION...Konieczny
FIRE WEATHER...Konieczny

For Northern Arizona weather information visit
weather.gov/flagstaff


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