textproduct: NWS Phoenix

KEY MESSAGES

- Above normal temperatures will continue through the forecast period with Extreme Heat Warnings in effect for portions of the area through mid week.

- Typical monsoon conditions will continue for the next few days with thunderstorm chances favoring Northern Arizona high terrain and portions of Southeast Arizona and low chances in the South Central Arizona lower deserts.

- High pressure will center itself over the region and strengthen late this week, resulting in hotter temperatures and another period of widespread Major to Extreme Heat Risk.

SHORT TERM /TODAY THROUGH SATURDAY/

A MCV can be seen on GOES mid-lvl WV imagery along with a large plume of moisture surging over Northern Mexico and southeastern AZ. This system is expected to track through south-central AZ through the overnight and early morning hours, with some isolated embedded showers already seen in southern Graham County moving northwestwards. This system will help the atmosphere regain some moisture with this morning forecasted PWATs between 1.7-1.9", and mixing ratios between 12-14 g/kg. Additionally, forecasted MUCAPEs throughout the morning are between 500-1000 J/kg across most of the lower deserts and upwards of 1500 in the eastern high terrain. Hi- res CAMs have also picked up on these conditions and is projecting morning thunderstorm/showers mostly in the eastern higher terrain but a few isolated thunderstorms/showers will be possible across southcentral AZ. By the afternoon moisture and CAPE values across south central AZ is expected to decrease, however the higher terrain will hold onto their moisture and instability with afternoon mixing ratios remaining above 12 g/kg and MUCAPEs upwards of 1500 J/kg. This will keep chances for thunderstorms and shower activity across the eastern higher terrain between 15-30%. The HREF only shows about a 10% chance of an outflow being produced out of the southeast, with winds above 35mph, this is in decent agreement with other models, such as the HRRR, where peak gusts this morning are forecasted between 20-25 mph. Increased chances of outflows will be this afternoon from the NE from storms in the higher terrain, where the HREF shows a 10-30% chance of winds above 35 mph, however many other models are currently not in good agreement with any outflows being able to extend down into Maricopa County.

Starting Wednesday thunderstorm activity is expected to decrease drastically as the region will begin to dry out and an exceptionally strong ridge builds over the Desert SW. By mid week PWATs will drop to between 1.4-1.6", then progressively lower to between 1-1.3" by Friday. This drying will be accompanied with near to at climatological max H5 heights (600 dam) that will drive temperatures back to near record highs by the end of the work week and into the start of the weekend. Temperatures will be fairly stable through midweek, especially across the western deserts, with afternoon highs in a 110F-114F range, between 2F-8F above daily normals for the typically hotter spots and today likely being the "coolest" of the next 7 days. The Phoenix metro will thankfully be a few degrees "cooler" compared to the western deserts, with afternoon highs today between 107F-110F. These temperatures are still above 4-6 degrees above normal, before steadily climbing throughout the remainder of the week. Friday and Saturday will be the hottest days this week with temperatures in south central AZ between 112F-117F, while the western deserts will be between 113F-120F. Overnight lows won't provide much relief either as throughout the week they will hold steady in the upper 80s to low 90s. These temperatures will produce wide spread Major to Extreme HeatRisk, which has lead to the decision to extend the Extreme Heat Warning for the Phoenix metro, Imperial Valley, and the Lower Colorado River Valley through Sunday, and expanding the Extreme Heat Warning to include the rest of the region starting Thursday, also going through Sunday.

LONG TERM /SUNDAY THROUGH TUESDAY/

By the end of the of the weekend and heading into the next work week, global ensembles point towards H5 heights weakening slightly to between 594-597 dams, and the center of the anticyclone over AZ, stretching into the Four Corners region. Although these heights will still remain above the 90th percentile of climatology for this time of year, resulting in temperatures remaining between 110F-114 in south central AZ, and the western deserts between 113F-117F. Widespread Major to Extreme HeatRisk will continue through Sunday, Major to localized Extreme Monday, and Moderate to localized Major by Tuesday. By Sunday moisture will begin to increase once again, with easterly to northeasterly flow aloft which will have potential for increased chances of thunderstorm development in northeastern AZ, with current PoPs between 20-30% in eastern Gila County. Unfortunately, with this outlook being so far in advanced conditions may change, so further evaluation will be needed throughout the week.

AVIATION

Updated at 1130Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Scattered showers and possibly a thunderstorm or two will remain in the Phoenix area through around mid morning with winds predominately out of the south southeast. Thereafter, we anticipate winds turning back out of the west mid to late morning with some gusty west winds to around 20 kts in the afternoon/early evening. BKN to OVC mid and high decks this morning will eventually scatter out by this afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH: Occasionally gusty wind will be the only weather concern through tonight under passing mid/high clouds. Confidence is good that wind directions will oscillate between SE and SW at KIPL while a southerly component will be preferred at KBLH. Gusts around 20 kt will be common at KBLH during the afternoon.

FIRE WEATHER

Typical monsoon conditions are expected through much of the forecast, with thunderstorm activity mainly favoring the high terrain of northern AZ and southeastern AZ and low chances (<10%) in the lower deserts of south-central AZ today. Above normal, temperatures will contribute to seasonally dry afternoon conditions each day through the first half of the week, before temperatures once again heat up during the second half of the week. Minimum RH values of 15-25% will be common through mid week before dropping into the 10-20% range late in the week as temperatures heat up again. Overnight recoveries will be fair most nights with RH values mostly in the 35-50% across lower deserts to 45-65% across southern Gila County. By Thursday MaxRHs will drop to between 20-30% across the lower deserts. Wind speeds should be fairly light through the period with only local afternoon gusts 20-25 mph.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Extreme Heat Warning until 8 PM MST Sunday for AZZ530-532-537- 540-542>544-546-548-550-551.

Extreme Heat Warning from 10 AM Thursday to 8 PM MST Sunday for AZZ531-533>536-538-539-541-545-547-549-552>563.

CA...Extreme Heat Warning until 8 PM PDT Sunday for CAZ567-569-570.

Extreme Heat Warning from 10 AM Thursday to 8 PM PDT Sunday for CAZ560>566-568.