Summit, AZ Weather

Synopsis

Temperatures at or slightly above normal through Thursday, then cooler than normal Friday into the upcoming weekend. An unsettled weather pattern will be around this week with daily chances of shower and thunderstorms with Wednesday afternoon through Thursday having the best chances for strong to severe thunderstorms. Main threat will be heavy rain, strong winds, and hail.

Discussion

A weak shortwave is moving from south to north this afternoon across eastern AZ. There is around 500-1300 j/kg of MLCAPE with enough share for some multicells and perhaps a transient supercelluar structure this evening. While widespread severe weather is not expected, a couple strong storms are possible. Main threat would be marginally severe hail and gusty winds. These storms should wane after sundown.

Tomorrow will be quite active as the large upper trof begins to influence the weather in the Desert Southwest. SPC has much of the area, with the exception of far western Pima County, in at least a Marginal Risk (level 1/5) with a small portion of NE Pinal, and much of Graham/Greenlee Counties in a Slight Risk (level 2/5). The main threats will be damaging wind gusts up to 60 mph, large hail, and very heavy rain. 0-6km shear of 30-45 kts and SBCAPE from the HREF of 1000-1800 j/kg will support supercells. With the low freezing heights, and potential for supercells, hail could easily exceed 1", with some isolated potential 2.0"+ in the strongest of storms. As for the tornado threat, the best parameters are NW of our area into the PSR/FGZ area, but we cannot rule out a tornado in our CWA. There is a 2-5% (probability of a tornado within 25 miles of a point) tornado risk for the entire CWA east of Lukeville/Ajo. Best chance remains across NE Pinal, northern Graham/Greenlee COs where parameters are highest.

While the severe storm threat is greater north of I-10, the threat technically goes all the way to the international border. However it will be more dependent on if we get development. If we see storms developing further south, they will have the threat for all modes of severe weather as well.

As for the heavy rain threat. CAMs generally show quick storm motion, but areas that see repeated cells could see localized flash flooding. Greatest threat for flash flooding north of I-10.

The severe and flash flood risk could go well into the night or all of the night Wed night into Thursday. Another round of severe weather is expected Thursday with a similar Marginal/Slight Risk area and all modes of severe weather possible.

Drier air moves in for Friday, though some lingering showers possible near the NM border, which could linger into the weekend as well.

Aviation

SCT-BKN clouds 6-10k ft agl this afternoon and overnight. SHRA/TSRA NE of KTUS and KDUG this evening. Increase in coverage of storms expected on Thursday. Strong to severe thunderstorms are possible for all TAF sites, with the greatest chance north of KTUS/KOLS/KDUG. Any shower or storm could produce brief MVFR/IFR in addition to strong winds to 50 kts, small to marginally severe hail and brief heavy rain. A low risk for a tornado is also possible, however the best chance would be north of TAF locales.

Fire Weather

Temperatures at or slightly above normal through Thursday, then cooler than normal Friday into the upcoming weekend. Wind speeds mostly less than 15 mph this week except for Thursday with southwest winds around 15 to 20 mph. Minimum relative humidity remains above 25-40+ percent in the valleys through the week with most days seeing anywhere from a 20-80 percent chance of showers with embedded thunderstorms at times as an unsettled pattern continues. There is a Marginal Risk for severe weather on Wednesday and Thursday from roughly I-10 south to the International Border and a Slight Risk for severe weather from roughly I-10 north Wednesday and Thursday.