textproduct: NWS Phoenix

KEY MESSAGES

- Dry conditions will prevail across the forecast area through the next several days with only isolated thunderstorm activity over the Eastern Arizona high terrain this weekend.

- Temperatures will be fairly stable through early this upcoming workweek, generally a few degrees above daily normals, with lower desert highs around 105 to 110 degrees.

- A better monsoon pattern for South Central Arizona sets up during the upcoming workweek, allowing thunderstorm activity to increase over the Eastern Arizona high terrain initially and introducing slight chances for lower desert storms by the latter half of the week.

SHORT TERM /TODAY THROUGH SATURDAY/

The zonally elongated subtropical high that sat almost directly overhead yesterday continues to retrograde westward early this morning, with current 500 mb RAP analysis placing its center just off the Northern Baja/SoCal Coast. With the influence of the high diminishing as it slides off to the west, a fairly strong gulf surge was able to occur, spreading over South-Central AZ and helping to increase dewpoint temperatures upwards of 60-65F so far early this morning. Further west across the Yuma area and Imperial Valley, dewpoint temperatures in excess of 70F have been observed. Though this is quite a shallow layer of moisture, radiative cooling at the surface will not be as efficient, making for another unusually warm morning. Forecast morning lows across the lower deserts are in the 80s and even lower 90s in central Phoenix this morning. Though different models show some discrepancies in the exact placement and strength of the aforementioned subtropical high as we head into this weekend, H5 heights are likely to fall in a 592-595 dam range through the next few days, maintaining slightly above average values for the time of year. This will translate to afternoon highs generally a few degrees above daily normals today and Saturday, around 105-110 for the lower deserts.

Thunderstorm activity will remain minimal across the state through Saturday, with the latest HREF membership showing essentially no convection this afternoon except near the international border in Cochise County. This is in large part due to dry, west northwest flow aloft today that will turn more northerly by Saturday, effectively scouring out moisture in the midlevels. In fact, PWATs are expected to drop below one inch across the entire forecast area by late Saturday. Despite this fact, some lingering low level moisture looks like it will be sufficient to spark high terrain convection Saturday along the Rim, White Mountains, and far Southeast AZ, but quite isolated in coverage.

LONG TERM /SUNDAY THROUGH THURSDAY/

By Sunday, ensembles hint at another high beginning to develop north of the area, turning the midlevel flow from north to northeasterly. This second high will likely develop into a Four Corners high later in the week. Latest guidance suggests a slight uptick in afternoon thunderstorm activity over the Eastern AZ high terrain Sunday, with a similar level of activity being maintained each day through Tuesday. Meanwhile, ensembles show PWATs gradually increasing over Southern AZ, with mean values upwards of 1.25-1.50" by the middle of the upcoming workweek. This would lead to gradually increasing convective coverage over the Southeastern third of the state. By Wednesday-Thursday, the high pressure aloft is also anticipated to slide over the Four Corners, which would help turn the flow east and then southeast over the forecast area. This could prove a much more favorable setup for monsoon thunderstorm activity for South-Central AZ in this situation, as we start the week rather moisture-starved, and better quality moisture will be situated to the south. With this evolution in mind, convective coverage will be on the increase across the higher terrain and foothills initially before chances increase across the lower deserts, more likely by the latter half of the week. A lot of details are still uncertain this far out, but the preponderance of ensemble guidance would suggest that some monsoon thunderstorm impacts (likely strong, gusty outflow winds and dust at first) will be possible across South-Central AZ late next week.

Temperatures will moderate closer to mid-July normals by the middle of the upcoming workweek as moisture gradually increases and H5 heights aloft fluctuate around 591 dam, near the climatological average for this time of year. As such, the latest NBM shows a continuation of lower desert highs in a 105-110 degree range through Monday, dropping into a 102-108 degree range by midweek.

AVIATION

Updated at 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT: No major aviation concerns are expected during the TAF period under mostly clear skies. Winds will follow familiar diurnal patterns, with some occasional breeziness tonight and once again tomorrow afternoon. The usual E'rly shift at KPHX still appears uncertain, but if one were to occur, it will be relatively brief. Otherwise, W'rly winds will prevail through Friday evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected over the next 24 hours under mostly clear skies. Sustained winds at KBLH should remain relatively elevated through tomorrow afternoon evening, with a couple period of gusts, some occasionally occurring during the morning hours, and once again Friday afternoon. Weaker winds are anticipated at KIPL. Familiar diurnal patterns direction wise will prevail.

FIRE WEATHER

Above normal temperatures and dry conditions will persist through the weekend. This afternoon, gusts upwards of 25-30 mph will be mostly confined to the high terrain of the eastern districts. Elsewhere, anticipate typical afternoon upslope breeziness for the time of year. Afternoon minRHs will generally bottom out between 15-20% areawide today and Saturday, and overnight recoveries will generally range between 40-60% tonight and drop to 30-50% Saturday night. Very minimal rain chances will exist through this weekend, with activity focused mainly across the Eastern AZ high terrain and southeastern third of AZ, with CWR <10%.

PSR WATCHES/WARNINGS/ADVISORIES

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