textproduct: NWS Phoenix

Update

00Z Aviation Discussion

KEY MESSAGES

- Temperatures will continue to cool through Wednesday, dropping to within a few degrees of normal and mostly staying steady through Friday.

- Chances for showers and a few isolated thunderstorms will continue through Wednesday, primarily focused over the higher terrain of south-central Arizona.

- Temperatures will warm again over the weekend into next week reaching low to mid nineties for highs.

SHORT TERM /Today through Wednesday/

The synoptic pattern continues to feature quasi-zonal flow over the southwest CONUS as thick mid and high clouds continue to stream over the region from the west. Anomalous moisture, with PWAT anomalies around 250% of normal, has allowed for midday showers to develop across south-central Arizona ahead of an approaching shortwave trough currently located off the coast of California. Thick cloud cover and a strong mid-level inversion has helped to limit our instability with CAPE values only around 100-200 J/kg this afternoon. Despite the lack of instability, isolated thunderstorms have developed this afternoon with this activity shifting toward the east/northeast. The dry subcloud layer in place may allow for a few of these thunderstorms to produce locally gusty winds. Rainfall amounts with these will remain low with a few areas observing less than 0.10" thus far.

The aforementioned shortwave trough will make its way toward the east and into our area later tonight. The approaching trough and its associated cold front will promote tightening gradients and increasing winds this evening and into the overnight hours. The strongest gusts are expected to reside across Imperial County in southeast California where gusts upwards of 30-35 mph are expected. A few isolated gusts in excess of 40 mph will be possible in this area, especially in southwest Imperial County. As the cold front progresses eastward across our area, hi-res guidance suggest a broken line of light showers will develop early Wednesday morning before completely exiting the CWA by midday. The best chances for seeing measurable rainfall will exist across the higher terrain north and east of Phoenix while little to no accumulation is expected across the lower deserts. Following the passage of the front, cooler, drier air will be ushered into the area allowing for clearing skies. Temperature readings will return closer to seasonal normals, though still remaining a few degrees above normal, as temperatures Wednesday afternoon are forecast to top out in the mid 80s across the lower deserts.

LONG TERM /THURSDAY THROUGH MONDAY/

Once the shortwave trough exits our region later Wednesday into Thursday, the region will fall under dry northwesterly flow leading to a gradual decrease in moisture across the region for the rest of the week and mostly clear skies. A Pacific trough passing well to our north on Thursday and Friday will help to keep the more mild temperatures in place as highs are expected to stay mostly in the mid to upper 80s. After this trough pushes into the Central Plains later Friday, upper level ridging building off the West Coast will start to filter into the Western U.S, moving fully over our region by Sunday. This next ridge will at least not be nearly as strong as what we have experienced over the past two weeks, but it will at least push daytime highs back above 90 degrees by Sunday. The latest NBM shows dry 90+ degree weather in place through at least the first half of next week.

AVIATION

Updated at 2305Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Breezy conditions along with lowering CIGs will be the main aviation concerns during the TAF period. Winds are expected to remain out of the W through the evening and much of the nighttime hours with gusts around 20kt through sunset. Speeds should relax a bit after sundown, but some lingering gusts cannot be ruled out. Confidence regarding wind directions decrease by the mid to late morning hours as some VRB conditions or even a brief switch to the E may occur. However, a continuation of a W'rly component is not out of the question either during this timeframe. CIGs will gradually lower overnight, bottoming out around 6-8k ft for a brief time. These lowering bases will be accompanied some light showers and virga. However, rain chances are too low (15-20%) to warrant inclusion of even VCSH in the TAFs at this time. Clouds should quickly scatter out behind the passage of a cold front.

Southeast California/Southwest Arizona including KIPL and KBLH: Periods of breezy to windy conditions will be the main aviation concern during the TAF window. At KIPL, gusts near 25-30kt will be common through most of the evening, relaxing eventually by early morning. At KBLH, gusts will not be as strong (around 20kt) and should diminish much earlier. Outside of a brief window VRB conditions a KBLH, some degree of a W'rly component will be favored through forecast. BKN-OVC skies will prevail tonight before eventually clearing out late Wednesday morning.

FIRE WEATHER

Modest moisture levels through Wednesday will continue to bring chances for showers and a few isolated thunderstorms focused mostly over the AZ high terrain. Humidities will remain slightly elevated with MinRHs between 15-25%. Afternoon wind speeds will increase slightly today into Wednesday with gusts 20-25 mph becoming common. Stronger gusts upwards of 30-35 mph will reside across Imperial County during this time with a few isolated gusts in excess of 40 mph possible, particularly across southwest Imperial County. Rain chances will completely come to an end by Thursday as gradual drying and warming occurs. Daytime breeziness will also continue through Friday with fire weather conditions worsening as MinRHs drop to below 15%.

PSR WATCHES/WARNINGS/ADVISORIES

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