textproduct: NWS Phoenix

KEY MESSAGES

- Above normal temperatures with localized Moderate Heat Risk will continue through Wednesday across the lower deserts with highs peaking at around 105 degrees today.

- Rain chances will increase over the next few days with the best chances focused across southeast California and southwest Arizona on Wednesday and Thursday and across south-central Arizona Thursday night into Friday.

- Temperatures are likely to return to normal later this week before slowly rising over the weekend into early next week.

SHORT TERM /TODAY THROUGH WEDNESDAY/

The weather pattern over the next several days is setting up to be quite complicated with the dissipating TC Mario driving good moisture northward into the Southwestern U.S. Currently, a weak ridge still resides over the region stretching across Arizona into portions of California, while a weak and dry upper level trough is spinning off the coast of northern Baja. TC Mario is still slowly moving to the north northwest roughly 350-400 miles west southwest of the southern tip of Baja. The south southeasterly flow in between TC Mario and the subtropical ridge to its east continues to advect good moisture northward, now nearing the southern border of Arizona. The latest analysis shows PWATs of 1.5-2.0" just south of our area. Some of this moisture is forecast to advect into our area later today, first reaching Yuma and then spreading through much of southeast California and southwest Arizona. This should help to spark off some very isolated showers and thunderstorms this afternoon across southeast California and southwest Arizona focused mostly over higher terrain features.

Temperatures today will again be quite warm with H5 heights sticking between 588-590dm. We are expecting highs across the lower deserts between 102-105 degrees this afternoon, or up to 5 degrees above normal.

From later today into Wednesday, much better moisture will stream into our area with PWATs increasing to between 1.4-1.8" by Wednesday evening. The best moisture will again be focused south and southwest of the Phoenix area with the Hi-res CAMs fixating on the best rain chances across Pima, Yuma, and Imperial Counties during the afternoon and evening hours. There is still a good deal of uncertainty with how fast the moisture surges northward on Wednesday. The latest HREF forecast MUCAPE of 500-750 J/kg for Wednesday over the aforementioned areas may allow for a few strong storms, but the instability may be underdone as the GFS is hinting at MUCAPEs of 1000-1500 J/kg over a small area. We will have to keep a close eye on how this evolves over the next 24-36 hours as the chance for stronger storms may increase.

LONG TERM /THURSDAY THROUGH MONDAY/

As we stated yesterday, model uncertainty was still quite high for later this week, so it's not surprising the forecast has shifted back to better rain chances for Thursday and Friday. Guidance remains confident in good low and mid level moisture seeping into the entire area by Thursday as the remnants of Mario inch toward or reach the southern California coast. The remnants of Mario are also likely to get incorporated into a larger scale trough off the coast with a jet streak strengthening across our region Thursday into Friday. Guidance is now showing even better upper level forcing for Thursday and Friday, as well as at least some modest upslope forcing into central Arizona. However, one negative factor is guidance shows a good amount of dry air aloft surging into our region from the southwest later on Thursday into Friday. This drier air aloft should inhibit heavy rainfall to a degree.

The latest forecast calls for scattered showers and isolated thunderstorms likely focused across southeast California during the first part of Thursday before spreading into southern and central Arizona by Thursday evening through the overnight hours Thursday. NBM PoPs of 40-60% are seen across much of the area Thursday and Thursday night. Rain chances for Friday are a bit more uncertain, but with the drier air likely moving in from the southwest chances are likely to be focused more across the Arizona higher terrain. Forecast QPF amounts for the entire event show the highest amounts of 0.5-0.75" across the western half of Maricopa County through northern Yuma and much of La Paz Counties. Higher elevations across southeast California could also see upwards of 0.5-0.75". Guidance also shows roughly a 5-15% probability of seeing an inch or more of rainfall from this event with the highest chances focused across western Arizona.

Temperatures later this week are certain to drop with the increase in moisture, clouds, and decent rain chances. The latest NBM guidance shows highs more on the lower end of guidance with readings mostly in the mid 90s for Thursday and Friday. As ridging gradually builds back over our region into the weekend and conditions gradually dry out temperatures are sure to rebound. Forecast highs are seen creeping back to around 100 degrees by Sunday and potentially even toward 105 degrees by the middle of next week.

AVIATION

Updated at 0506Z.

South Central Arizona and Southeast CA including KPHX, KIWA, KSDL, KDVT, KBLH and KIPL:

Winds will continue to follow typical diurnal patterns with speeds remaining mostly aob 8 kts. Periods of calm and vrb winds will also be likely, especially at the SE California terminals and prior to diurnal wind shifts. Uncertainty increases tomorrow afternoon and evening with guidance indicating the potential for an outflow to push into the metro tomorrow evening from the SE. For KIPL and KBLH, a few aggressive models support isolated convection tomorrow afternoon near the terminals, however, have not added mention of this or any associated outflows given the low confidence. Otherwise, mostly clear skies will persist through much of the period.

FIRE WEATHER

Today will again bring above normal temperatures while moisture continues to increase. Even better moisture and cooling temperatures are then expected going into the latter part of the week as rain chances increase across the entire area. The best chances for rain are likely to fall on Thursday and Friday. MinRHs today will still dip down to around 20% before steadily increasing to around 40% late this week. Winds will remain light over the next few days with directions mostly following diurnal trends.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...None.