Key messages
- Thunderstorms capable of severe weather and flooding will exit
Update
00Z Aviation Discussion.
Key Messages
through eastern Arizona this evening with drier air surging into the region.
- More benign weather conditions will filter into the area Friday and through the weekend with only a few lingering showers over mountain locations in Arizona.
- Below normal temperatures through early next week will warm closer to the seasonal average by the middle of next week.
Short Term /Today Through Saturday/
Deep negative height anomalies were finally moving inland across southern California with a notable trough axis rotating into SE California/SW Arizona. A strong jet core has shifted to the eastern side of the larger circulation ensuring further lifting of cold core aloft towards southern Utah while allowing deep downstream meridional flow to veer more W/SW. While much of the eastern CWA remains in the right rear jet quadrant favorable for synoptic ascent this afternoon, the propagation of the aforementioned trough axis will place the region under growing subsidence after this evening. Concurrently, a plume of ample moisture remains situated from the Phoenix metro eastward with PWATS around 1.25" and low level mixing ratios 10-12 g/kg yielding MLCape 1000-1500 J/kg. Kinematic fields continue to support organized supercell structure given 0-6km shear above 50kt while hodographs increasingly becoming straight-lined would point towards splitting cells, and similar to yesterday preferring left movers producing very large hail (sufficient 400-600 J/kg CAPE within the -10C to -30C hail growth region as well). While a tornado threat will persist in Gila County with a Watch through 8 pm, weakening 0-1km shear vectors and higher LCL's may keep the greater threat to the east and north of Gila County.
Recent objective analysis depicts the wedge of dry air behind a theta-e boundary and in association with the deeper veered winds already bisecting the Phoenix metro early this afternoon. This boundary will continue to progress eastward through the evening eroding instability and eliminating the convective threat beyond mid evening. It's not out of the question a lingering shower could affect eastern Arizona high terrain tonight, however HREF and REFS output offer only minimal support for this outcome. On Friday, a secondary vorticity center emanating over the East Pacific will dive into the mean trough position across the SW Conus creating a quasi- cutoff low that will persist through Saturday. With better moisture already scoured from the area, only mountain location may be capable of squeezing out a few diurnal showers under the cold core Saturday with lower elevations remaining dry. This system will ensure H5 heights remain sequestered under 572dm through Saturday with excellent forecast confidence of temperatures solidly 10F below normal.
Long Term /Sunday Through Thursday/
Model guidance suggests the aforementioned cutoff should remain over the region through the entire weekend, but continuing to weaken allowing the airmass to slowly warm over time. NBM forecast highs Sunday show readings rebounding into the lower 80s over the western lower deserts to near 80 degrees in the Phoenix area. By Monday, the trough is likely to finally push east of the region with modest upper level ridging prevailing over the Desert Southwest. The increased heights and continued dry conditions should push daytime highs back into the normal range (mid 80s) going into the middle of next week.
Aviation
Updated at 2325Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected through the forecast period under gradually clearing skies. Winds will remain SW to W through this evening with occasional gusts up around 20 kt expected at all terminals through sunset. Thereafter, winds will relax and switch back out of the E-SE late tonight. FEW to SCT clouds around 6-7 kft will continue to dissipate as dry air moves into the area.
Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation weather concerns are anticipated through the forecast period. Winds will favor a SW-W component at KBLH and W-NW at KIPL. Intermittent gusts up to 20-25 kts will be common over the next few hours with a few gusts exceeding 30 kts possible at KIPL. Otherwise, gusts should diminish by midnight and speeds will fall to 10 kts or less. FEW to SCT clouds, mostly aoa 7 kft, will continue into the evening before becoming clear overnight.
Fire Weather
Strong to severe thunderstorms with heavy rainfall will remain possible over eastern districts through this afternoon before rapid drying spreads through the area this evening and tonight. The heaviest rainfall will be focused more across higher terrain areas north and east of Phoenix. MinRHs today will again be in a 30-60% range before dropping more into a 25-40% range for Friday and Saturday as cooler air settles into the region. Gusty west winds upwards of 25-30 mph will be possible across the western districts through this evening with winds becoming light starting tonight. Overall quiet weather conditions are forecast for this weekend into next week with fairly stable humidities and temperatures rebounding back into the normal range early next week.
Psr Watches/Warnings/Advisories
AZ...Flood Watch until 11 PM MST this evening for AZZ545-547-552- 556>558-560>563.
Flood Watch until 5 PM MST this afternoon for AZZ541-549-555.
CA...None.
SHORT TERM...18 LONG TERM...18/Kuhlman AVIATION...Salerno FIRE WEATHER...Kuhlman