textproduct: NWS Flagstaff

SYNOPSIS

Deep monsoonal moisture will remain over the area through this weekend and well into next week. With this moisture comes the daily threat of thunderstorms, along with the risk for locally heavy rainfall and flooding. With the added moisture and cloud cover, daytime temperatures will remain below normal.

DISCUSSION

We are locked in a pattern that shows no signs of changing and considering how badly the region needs water, this is largely a good thing. The region will remain in a very moist air mass, even with respect to the Monsoon Season, with both PW and surface dew point values about as high as is possible. Northeast through easterly steering flow will also persist, at least into early next week. This steering flow may transition to more of a southeasterly direction later next week.

The current steering flow heavily favors locations just to the southwest, south and west of the central Mogollon Rim. A secondary area usually forms later each day across Apache and Navajo counties or over western New Mexico. These secondary areas are what supports nocturnal convection, which should be more active tonight than last night. This is evident in the latest model guidance aided by increased sun over northeast AZ this morning.

Despite all the favorable mechanisms to produce heavy rain, we are also seeing large areas of rain-cooled air, rain-cooled ground and extensive debris cloud cover each day/night. These factors can prevent stronger and more widespread convection from forming and therefore limit the amount of storms that can produce flash flooding. This and the lack of any clear forcing mechanism will keep FFA issuances away for another day, at least. By early next week, an easterly wave may improve shear and storm motion, potentially raising the risk for flash flooding and hail production.

AVIATION...Saturday 18/18Z through Sunday 19/18Z

Another active day of monsoon TS is in store. Expect scattered to numerous SHRA/TSRA with isolated +TSRA today. Stronger storm cells will produce brief MVFR and IFR. +RA with reduced CIG/VIS are the greatest storm threat today, but gusty outflow winds up to 40 kts and hail are also possibilities. Rounds of SHRA/TSRA likely to continue through the evening hours. Outside of TS, expect light winds 5-10 kts.

OUTLOOK...Sunday 19/18Z through Tuesday 21/18Z...Expect scattered-numerous SHRA/TSRA and isolated +TSRA each day, storms most numerous in the afternoon hours. Any stronger storms will produce brief MVFR and IFR. Some IFR low clouds and BR possible, mainly for overnight hours. Outside of storms, expect light winds around 5-10 kts.

FIRE WEATHER...Sunday and Monday

Expect a continuation of the active monsoon pattern into next week with rounds of showers and thunderstorms each day. Primary storm concerns will be heavy rain and flash flooding, though erratic outflow winds are also possible. Outside of storms activity, expect light winds.

Tuesday through Thursday...Active monsoon conditions continue with daily chances for showers and thunderstorms, Expect generally light winds outside of any storms. Most storms will produce wetting rain with isolated to scattered flash flooding.

FGZ WATCHES/WARNINGS/ADVISORIES

None.