textproduct: NWS Phoenix

UPDATE

Updated Aviation

KEY MESSAGES

- Dry weather will return to the region through the weekend with temperatures hovering a few degrees above normal.

- A period of unsettled weather may return during the middle of next week with chances of light rain returning.

SHORT TERM /Today through Saturday/

Shortwave energy over central Utah early this morning was cresting a prevailing SW Conus ridge, and will quickly propagate into the plains over the next 24 hours. This will leave the forecast area under growing large scale subsidence with high pressure re-building into the region. While this transition represents a general drying trend, thick boundary layer moisture remains trapped over much of the CWA this morning in the form of low clouds and patchy fog. Forecast soundings and satellite trends suggest more prevalent low clouds vs dense fog, though cannot discount periods of fog in the most favorable spots this morning (and to a lesser extent Saturday morning). Otherwise, scattered clouds will persist through the afternoon with excellent confidence of temperatures reaching 3F to 6F above normal. Low level moisture will partially scour Saturday as H5 heights increase modestly allowing temperature to warm a couple degrees above persistence.

LONG TERM /Sunday through Thursday/

The hemispheric longwave pattern will only be slow to advance through the middle of next week owing to stubborn downstream North Atlantic blocking. Ensemble membership remains in excellent agreement indicating low amplitude ridging prevail across the SW and central Conus while East Pacific troughing only slowly edges towards the West Coast. A series of lead shortwaves will almost certainly eject from the longwave trough position early in the week, however only de-amplify and lift into the Great Basin bringing a cold front onshore into cntrl/srn California, but no further. A more defined cold core should drop towards a developing weakness in the midlevel height field into the Southwest during the middle of the week. While a handful of ensemble members still depict an earlier arrival (particularly in the CMC suite), the trend among the preponderance of membership suggests a slower PV passage sometime in the Wednesday time frame.

While low level moisture will not completely be eliminated early in the week, warmer air aloft and rain shadow effects from prevailing W/SW flow will limit any inland deep saturation and rain chances. As usual, NBM POP bias in SE California becomes evident bleeding higher chances off mountains to the west, and have trimmed values back appropriately. It would not be uncommon for thicker cirrus decks to impact daily highs at some point early in the week, however numerical guidance remains consistent in advertising readings a few degrees above the daily normals into the middle of the week. Uncertainty in the precise track and intensity of the PV anomaly moving into the region midweek limits a larger POP mention in the official forecast with the majority of model output leaning towards another weakening wave and limited ascent/precipitation potential.

AVIATION

Updated at 1100Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Forecast confidence is only low to moderate this morning due to a combination of low clouds and fog around the region. Cigs 6K-8K AGL should be the most common feature this morning, however patches of cigs near 3K ft have been reported, as well as pockets of shallow fog outside the metro. Probabilities of direct weather impacts and flight restrictions to any specific aerodrome are too low to include at this time. Otherwise, scattered decks 040-060 are possible through mid/late afternoon before dissipating with sunset. Light east winds should attempt a westerly switch this afternoon, however may remain variable for extended periods.

Southeast California/Southwest Arizona including KIPL and KBLH: Patchy fog with reduced visibilities may become an issue this morning, however coverage and magnitude of any potential direct impact remains uncertain. Have maintained a VCFG mention with this TAF package with lower probabilities of worsening flight categories through 17Z (IFR or lower). Forecast confidence is better beyond this morning with clearing skies and light N/NW winds through Saturday morning.

FIRE WEATHER

Moisture levels will remain seasonally elevated through much of next week with minimum afternoon readings only falling into a 40-60% range. This will follow excellent overnight recovery greater than 75%. Very light winds with several periods of nearly calm readings may increase somewhat during the middle of next week. A dry weather pattern through the first part of next week may become more unsettled during the middle of the week with increased chances for wetting rain.

PSR WATCHES/WARNINGS/ADVISORIES

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