textproduct: NWS Phoenix

KEY MESSAGES

- A weather system will bring increased rain chances and cooler temperatures to a good portion of Arizona tomorrow.

- Dry and warm conditions are expected this weekend with highs mostly in mid 70s across lower deserts.

- A stronger weather system should bring even better rain chances early next week along with noticeably cooler temperatures.

SHORT TERM /TODAY THROUGH FRIDAY/

Today the region will continue to be under the influence of H5 heights ranging between 570-576 dam. Thus today's afternoon high temperatures are expected to be in the mid to upper 70s across the lower deserts, and upper 60s to lower 70s in the higher terrain areas.

Tomorrow an upper level low, currently to our SW, will begin to move onshore, lowering heights aloft. This will in turn cool the region down to near normal, seeing afternoon highs near 70 degrees across the lower deserts. As this low moves onshore and into our region moisture will increase, peaking at ~200% of normal with PWAT values near 0.8-0.85". The upper level low will bring a weak swath of PVA over Arizona with the core of the energy mostly contained to our south in Northern Mexico. However, the energy over Arizona, in conjunction to the moisture advection, will be enough to see light showers across Eastern Maricopa County and east of the Metro into the higher terrain areas starting early Friday afternoon into the early evening hours. Models are in good agreement that the eastern portions the region will see precipitation, however, the total QPF accumulations are not impressive. Most of Eastern Maricopa County is only expected to see between 0.01-0.03" with some areas seeing no rainfall at all. Meanwhile, east of the Metro into the high terrain can expect to see between 0.1-0.3".

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Once the trough exits the region to the east Friday night into Saturday, ridging will quickly move in from the west, lasting through Sunday. The ridge will bring drying conditions with sunny skies on Saturday before clouds start to move in again Saturday night. Temperatures should also bounce back this weekend with highs Saturday in the lower 70s in Phoenix to the upper 70s in southeast California followed by the mid to upper 70s on Sunday.

A more significant upper level trough is expected to dive southward off the West Coast this weekend before sending considerable precipitation into much of California on Monday. Guidance shows near record low H5 heights well west of southern California and northern Baja early Monday before the system starts to weaken as it moves closer to the California coast. A rather strong upper level jet is also forecast to impact much of the Southwestern U.S. Monday into Tuesday and this will help to drive much of our expected precipitation chances later Monday into Tuesday. Even though guidance heavily favors the trough opening up on Monday with much of the PV energy missing our area to the northwest, we are still likely to have a decent mid-level front move through at some point Monday night.

Ensembles are now in good agreement showing anywhere from 175-225% of normal PWATs pushing through the area along the front with low level mixing ratios as high as 7 g/kg. Current indications also show strong southwesterly upslope flow which will help to drive more efficient rain production in upslope areas across central Arizona. That being said, there is still enough uncertainty to have doubt on the rainfall amounts and the exact timing. The latest ensemble mean QPF for early next week generally shows up to 0.1" for the western lower deserts, 0.25-0.50" for the south-central Arizona lower deserts, to as much as 0.75-1.00" over the Arizona higher terrain. Snow levels will gradually lower early next week, but for now mostly stay above 6500' providing little chance of snow in our CWA. Temperatures should at least lower back to around normal by next Tuesday or Wednesday and likely stay fairly stable through the rest of next week. The unsettled weather pattern is likely to continue through the rest of next week with one or two more potential weather systems either impacting our region or brushing by just to the north.

AVIATION

Updated at 1700Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Lowering cigs and increased shower chances Friday afternoon will be the primary weather impacts this TAF period, however unusual timing and uncertainty in wind shifts may also create operational issues. Confidence is good that a light SE or variable wind direction will become W/SW mid/late afternoon today. Confidence in wind directions becomes low beyond mid/late evening with some terminals (i.e. KPHX) potentially retaining the westerly component until around sunrise Friday before shifting to the S/SE. Midlevel cloud decks should thicken and lower through the day Friday with the potential for isold SHRA and erratic wind directions Friday afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH: No major weather impacts will exist through Friday afternoon under thickening and lowering mid/high cigs. Winds will favor a N/NW component through the period, however may be variable at times. The lowest cigs and best chances of a few SHRA will occur at KBLH later Friday morning, though likely with limited operational impacts.

FIRE WEATHER

Today will bring dry conditions and continued above normal temperatures. Starting tomorrow, an incoming weather system will bring temperatures to near normal and rain chances (~50-80%) across the eastern districts. MinRH values today will mostly fall between 20-30% before briefly rising on Friday to 35-50% for at least the eastern districts. 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.