textproduct: NWS Phoenix

UPDATE

06Z Aviation Discussion

KEY MESSAGES

- A changing weather pattern will help to bring some unsettled weather into the region late this week with rain chances on Friday for portions of Arizona.

- After dry and still warm conditions this weekend, another weather system may bring even better rain chances early next week along with noticeably cooler temperatures.

SHORT TERM /TODAY THROUGH THURSDAY/

Satellite imagery early this afternoon reveals that the overall synoptic pattern remains largely unchanged from this morning, with a deep trough just off the coast of California with two distinct PV centers. The more northern PV center just started to move onshore in north central California. Visible satellite imagery also shows an abundance of cloud cover associated with this trough with the leading edge of the cloud cover streaming into Arizona. The additional cloud cove today has allowed for slightly cooler temperatures from yesterday. As of 1pm MST/12pm PST, temperatures are sitting in the 70s across the lower deserts and in the 60s across the higher terrain areas. with a couple more hours of heating, temperatures are expected to top out in the mid to upper 70s across the lower deserts and in the upper 60s to low 70s across the higher terrain. The trough will weaken and slowly move east/southeastward tomorrow, but heights aloft will largely remain unchanged and may only drop 1-2 dm. Therefor, temperatures tomorrow will are forecasted to be very similar to today. With afternoon high temperatures in the mid to upper 70s across the lower deserts and in the upper 60s to low 70s across the higher terrain.

There has been a noticeable increase in moisture over our area out ahead of the trough, as is evident by the mid and high level clouds and dew points in the 40s. Additionally, PWATs are in a 0.4-0.6" range across our region. Despite this increase in moisture, with the PV centers and associated trough remaining west of our area, no precipitation chances are expected through Thursday.

LONG TERM /FRIDAY THROUGH EARLY NEXT WEEK/

The trough to our west is expected to weaken tonight into Thursday before finally shifting into our region on Friday. Models are still uncertain with how much energy and moisture will be available for our region on Friday, but they are mostly trending toward slightly better moisture briefly advecting into southern and central Arizona for Friday. The EPS is a bit more on the drier side, but it has been trending upward with PWAT anomalies between 175-200% from Phoenix and areas to the east. The other unknown is the exact track and strength of the main vort center on Friday with the GEFS showing stronger energy. The GEFS mean QPF for Friday has around 0.10-0.15" for Phoenix to as much as 0.50" over the higher terrain east of Phoenix, whereas the EPS only has around 20% of the GEFS's QPF. Considering the trends, the EPS may be the outlier and the latest NBM PoPs are likely too low. The timing for the potential rain on Friday looks to be from around mid morning through early evening. Temperatures may also drop a good deal on Friday across south-central and eastern Arizona due to the return of cloudy skies and the rain potential. Models have been trending even cooler because of the increasing rain potential with forecast highs now only in the upper 60s to around 70 degrees for Phoenix on Friday.

Upper level ridging is then forecast to quickly shift eastward into the region Friday night into Saturday and lasting through most of Sunday. This will bring drying conditions and at least overall sunny skies on Saturday. Temperatures should also bounce back this weekend with highs mostly in the mid to upper 70s across the lower deserts. Saturday night into Sunday should however bring partly to mostly cloudy skies as the next deep trough will be settling in off the coast of California. This trough is forecast to become quite deep with negative upper level height anomalies dipping below the 10th percentile of climatology off the coast of California Sunday through at least Monday. Model uncertainty is again a big problem with this next weather system as it remains quite possible that much of its energy may miss our region to the north. The NBM looks to be too aggressive with precip chances early next week considering the uncertainty, so PoPs have been trimmed back some. There could also be a second follow-on shortwave that may bring another round of precip chances as late as next Wednesday or Thursday. Guidance continues to show cooler air moving into the region during the first half of next week, potentially bringing temperatures back to or even slightly below normal for this time of year.

AVIATION

Updated at 0525Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will continue to exhibit light and diurnal tendencies with sporadic window of VRB to calm conditions. SCT-BKN skies during the front half of the forecast will give way to more BKN-OVC coverage by Thursday afternoon/evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are anticipated during the next 24 hours under generally BKN skies. Winds will favor a NW'rly component at both terminals with perhaps a brief switch to the SW at KBLH Thursday afternoon. Periods of VRB to calm conditions can be expected throughout the forecast window.

FIRE WEATHER

The weather pattern is slowly becoming more unsettled as a weather system will remain just west of our area through Thursday. Slightly cooler temperatures and increased clouds will be seen today before the system eventually passes across the region on Friday bringing rain chances to the eastern districts. Additionally this system will cool temperatures to near normal on Friday. MinRH values will continue to be between 20-35% through Thursday before briefly rising on Friday. Occasional breeziness, especially across the western districts, will be common during the next several days. Drying conditions and warming temperatures are expected over the weekend before another weather system may impact the region early next week.

PSR WATCHES/WARNINGS/ADVISORIES

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