textproduct: NWS Phoenix

KEY MESSAGES

- Departing high pressure will keep temperatures across the region around 4 to 8 degrees above daily normals today.

- A weather system will traverse the Great Basin, resulting in gusty winds across portions Southeast California and the Lower Colorado River Basin this afternoon.

- Temperatures will cool back to near normal in the wake of the passing weather system with continued breezy conditions for the remainder of the week and into this weekend.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Current objective analysis reveals the Desert Southwest in a transition zone as departing high pressure flanks us to the east and an approaching closed low inches closer to the Pacific Coast. Our forecast areas will find itself influenced by each of these weather regimes this afternoon as the ridge helps keeps temperatures relatively elevated while the western disturbance generates breezy to locally windy conditions. Lower desert highs will remain 4-8 degrees or so above-normal for this time of year, which translates to a continuation of afternoon highs in the 90s for the lower deserts. As the latter feature pushes eastward, our regional pressure gradient will tighten up, which will, as mentioned above, usher in the return of enhanced winds for parts of the region, especially out in SE California and the Lower Colorado River Valley. Wind Advisories have been posted for Western Joshua Tree NP and SW corner of Imperial County due to the high confidence of winds exceeding 40 mph. Advisory level gusts will be possible over other parts of SE California, but should be confined to higher ridge top areas. Peak gusts for lower elevation areas should generally range around 30-35 mph. These strong winds will also up the potential for areas of blowing/lofted dust which could result in hazardous travel along stretches of I-8 and I-10. Elsewhere, breezy conditions will exist, but readings should be closer to 20-25 mph.

The previously mentioned low will eventually work its way onshore early Wednesday, weakening as it does and transitioning to an open wave trough. The base of the disturbance will pass well to our north, but will have at least some influence on regional conditions for at least one more day. One noticeable change from the day prior will be the relatively cooler temperatures as highs for lower desert areas will be mostly in the middle to upper 80s, much closer to normal for mid to late April. This system will also provide one more round of breezy conditions for parts of the region, but this time the focus shifts more towards the high terrain of eastern Arizona, where gusts will peak around 25 mph, with gusts closer to 30 mph for the highest ridgetops. The typical wind prone areas of SE California will see some residual gusts as well, but they will not be nearly as strong as today.

LONG TERM /THURSDAY THROUGH MONDAY/

Ensemble members and deterministic guidance continues to indicate quasi-zonal flow returning to the Desert Southwest Thursday and Friday which will result in temperatures remaining near to slightly above normal. A compressed 500 mb hght gradient will prevail over the Desert Southwest resulting in continued breezy to locally windy conditions through the end of this week with afternoon gusts reaching 20-30 mph. A progressive pattern will continue into this weekend as a series of mostly dry weather systems passes north of the region. The strongest shortwave looks to arrive on Sunday which will cool temperatures to around 3 to 5 degrees below normal across the region. Both the mean of the GEFS and EPS show negative hght anomalies persisting over the Desert Southwest well into next week which will keep temperatures at least near normal to slightly below normal to finish off the month.

AVIATION

Updated at 1734Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation concerns are expected through the TAF period. mostly diurnal trends with a brief period of southerly winds before the anticipated westerly shift for the afternoon hours. Gusty winds this afternoon will be common with gusts between 20-25 kts, relaxing by late this evening where the overnight wind speeds will be aob 10kts. A late shift to easterly is expected by sunrise tomorrow. Skies will be mostly clear with the exception of FEW passing high clouds through out the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH: Strong, gusty winds late this afternoon/evening will be the primary weather concern as thicker high cirrus decks gradually clear through out the period. Confidence remains high that westerly winds at KIPL will remain in place while southerly/southwesterly winds will be preferred at KBLH. Gusts 20-25kt will materialize this afternoon with gusts likely strengthening above 30kt at KIPL during the evening.

FIRE WEATHER

A progressive pattern with multiple dry weather systems passing north of the region will result in breezy conditions and periods of elevated fire weather throughout this week. Relative humidity is not expected to fluctuate much, bottoming out around 8-15% each afternoon. Overnight recoveries will remain poor to fair over the next several nights. The strongest winds will reside in SE California this afternoon and evening where gusts up to 25-35 mph (locally higher) will be possible. These stronger winds coupled with very dry conditions (RH as low as 10%) will result in a brief period of near critical fire weather conditions this afternoon. Widespread breezy conditions with gusts around 20-30 mph will continue each afternoon through the remainder of this week, resulting in persistent elevated fire weather.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...Wind Advisory until midnight PDT tonight for CAZ560.

Wind Advisory until 8 AM PDT Wednesday for CAZ562.