textproduct: NWS Flagstaff

SYNOPSIS

Showers and thunderstorms continue today, before activity slowly tapers down to isolated coverage later this week and into the weekend. Once the activity slows down, expect daytime high temperatures to soar, likely reaching the warmest readings so far this year, by the weekend.

DISCUSSION

An impressive convective outburst on Monday evening has led to the development of a large MCS over northern Mexico and southeastern Arizona this morning. The MCS is largely decaying, but still contains decent convective elements. Because of this MCS, a fairly well-defined MCV is also expected to develop this morning. This MCV will then track across southern Arizona today and up through the Lower Colorado River tonight/early Wednesday.

This type of thing ca wreak complete havoc on the forecast. Now, we must factor in a large amount of debris cloud, how will that inhibit convection today? It will also drive higher dew points northward for the remainder of the morning. The entire time this is happening, the mid-level high to our east temporarily weakens a bit, which will potentially destabilize the atmosphere, when compared to Monday.

All these factors could easily lead to a more active day today, but we have rain-cooled air and debris cloud to deal with. Much of the debris cloud and potential morning showers will affect the southern portions of our CWA, but the northern zones may very well get that cherished, sunny start.

The best guess at this time will be for convective showers to move into the CWA this morning, mainly south of I-40 and into parts of Yavapai County. Expect a delayed start elsewhere. Conditions north of I-40, all the way up to the Kaibab, may become quite active by afternoon, due to the factors mentioned above and the potential for a warmer and sunnier start.

After today, the high begins to move westward and strengthen, This slowly introduces drier, mid-level air and subsidence, activity will slow down. We don't expect a total stop, but it will be slow through the weekend. The high may return to a more favorable location by next week, with easterly steering flow returning, but much can change in a week and we will see.

Additionally, once the high relocates and strengthens, along with the Monsoon pause/slow down, temperatures will soar. We expect many areas to reach the warmest readings so far this year. The various heat products that have been issued are appropriate.

AVIATION...Tuesday 28/12Z through Wednesday 29/12Z

Mainly VFR conditions. SCT SHRA/TSRA through 03Z Wednesday. Greatest coverage across or near higher terrain features. Brief MVFR/IFR conditions and gusty, erratic winds in stronger storms. Outside of storms, expect generally light or terrain driven winds.

OUTLOOK...Wednesday 29/12Z through Friday 31/12Z...Mainly VFR conditions. ISO-SCT SHRA/TSRA from 18Z-03Z each day, with greatest coverage across or near higher terrain features. Brief MVFR/IFR conditions and gusty, erratic winds in stronger storms. Outside of storms, expect generally light or terrain driven winds.

FIRE WEATHER...Tuesday and Wednesday

Active Monsoon conditions are expected today, with a slow downturn beginning Wednesday. Expect mainly light winds outside of thunderstorms, but trending toward westerly through southwest 5 to 15 mph over higher terrain. Daytime temperatures stay around normal, a bit above normal where it does not rain.

Thursday through Saturday...A continued downturn in Monsoonal activity is expected through this period, although isolated showers and thunderstorms remain possible over higher terrain. Temperatures will rise significantly during this period, with many areas seeing the warmest conditions so far this year. Winds will be generally light and variable, at 5 to 15 mph.

FGZ WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning from 10 AM MST /11 AM MDT/ Friday to 8 PM MST /9 PM MDT/ Sunday for AZZ005-038, as well as AZZ037 below 4000 feet.

Extreme Heat Warning from 10 AM Thursday to 8 PM MST Sunday for AZZ006 below 4000 feet.