368 
FXUS65 KFGZ 091041
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
340 AM MST Mon Mar 09 2020

.SYNOPSIS...After a dry and mild day today, expect the remainder of 
this week to feature periods of rain and high elevation snowfall. 
Snow levels will remain above most high country population centers 
through Wednesday night, before lowering into Thursday and Friday. 
Area creeks, streams, washes and rivers will likely rise throughout
the week.

&&

.DISCUSSION...A weak s/wv ridge traversing the area early this 
morning will move into New Mexico this afternoon, as flow aloft 
turns neutral head of our next low pressure system. The next low 
will stay out in the eastern Pacific for a few days, but it will 
also tap into a sub-tropical moisture plume as early as tonight.

This plume will be the first wave of precipitation for Arizona, the 
first in a long week of precipitation events. Expect rainfall to 
arrive toward daybreak Tuesday, with the southern and central zones 
most affected. This will be a warm airmass, with largely light to 
moderate stratiform precipitation. There will a a tricky period 
during the first few hours, where evaporative cooling may allow a 
few snow pellets down to around 7500 feet, but snow levels will 
quickly rise heading into Tuesday.

The low then slowly pushes east Wednesday and Thursday, ejecting 
through Arizona on Friday. It will be a complicated movement, the 
low initially ejects a small piece of energy northeastward early 
Wednesday, before reinforcing jet energy and cold air causes the low 
to retrograde, strengthen and consolidate Thursday. The low then 
ejects in its entirety on Friday.

This little dance and wobble is what will bring precipitation to our 
area in waves, rather than a continuous event. By the time the newly 
consolidated low ejects, a dynamic cold front will accompany the 
passage, along with some mid-level instability. This time frame will 
be the most susceptible to flooding, as it will occur after several 
days of stratiform rainfall.

This is the type of pattern that will favor the "first upslope" 
regions of our CWA. This means that with a saturated airmass and a 
saturated desert boundary layer, the first rise in terrain will see 
the most QPF. Specifically, this would be the higher terrain of 
southeast Yavapai county, as well as far northeastern Maricopa 
county heading into Gila county. This pattern also favors the 
northern reaches of Oak Creek Canyon.

Expect to see widespread rainfall amounts of 1 to 2 inches, with the 
areas mentioned above possible exceeding 4 inches. The time frame we 
are talking about is Tuesday through Friday.

Additionally, temperatures aloft fall late Thursday into Friday, 
which will lower snow levels just enough to affect high elevation 
populations centers. The thinking now is that this will be toward 
the end of the event, keeping impacts from snowfall at a minimum.

After a dry and warm weekend, long range models are now advertising 
an active pattern early next week. Could be an interesting month.

&&

.AVIATION...For the 12Z package...Expect mainly VFR conditions for 
the next 18 hours. Some areas of MVFR/IFR ceilings being observed 
along the Mogollon Rim this morning and will continue through 15Z. 
Broken cirrus this afternoon will give way to lowering ceilings 
after 03Z Tuesday as chances of precipitation increase from south to 
north tonight. Light and variable surface winds will become south to 
southwest at 8-12 knots with gusts to 20 knots between 17Z and 01Z 
Tuesday. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Slightly warmer conditions return today. A wetter
pattern will begin this evening with increasing chances for wetting 
rains from south to north into Tuesday. Snow levels tonight will be 
above 7500 feet and rise to above 8500 feet by Tuesday afternoon.

Wednesday through Friday...The period of wet conditions and 
seasonable temperatures will continue Wednesday and Thursday. Snow 
levels may decrease early Friday morning, as temperatures cool.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

PUBLIC...Peterson
AVIATION...Lynum
FIRE WEATHER...Lynum


For Northern Arizona weather information visit
weather.gov/flagstaff