textproduct: NWS Flagstaff

SYNOPSIS

Deep monsoon moisture will remain over the area through the 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, but there are so many variables in play, it's hard to know for sure.

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, but tonight is quiet, mainly due to the lack of well-defined outflows. One of the "problems" with a saturated air mass is that organized outflows no longer form and we end up with a less organized environment.

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 18/12Z through Sunday 19/12Z

Expect SCT-NMRS SHRA/TSRA and ISOLD +TSRA through the period, 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, sfc winds are not anticipated to affect flight operations.

OUTLOOK...Sunday 19/12Z through Tuesday 21/12Z...Expect SCT-NMRS SHRA/TSRA and ISOLD +TSRA through the period, 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, sfc winds are not anticipated to affect flight operations.

FIRE WEATHER...Saturday and Sunday

Expect a medium to high grade monsoon environment, with generally light winds outside of outflow and thunderstorm activity. Most storms will produce wetting rain with stronger storms producing localized Flash Flooding.

Monday through Wednesday...Chances for showers and thunderstorms continue, generally light winds outside of outflow and thunderstorm activity. Most storms will produce wetting rain with stronger storms producing localized Flash Flooding.

FGZ WATCHES/WARNINGS/ADVISORIES

None.