textproduct: NWS Phoenix

UPDATE

Updated 12Z Aviation Discussion.

KEY MESSAGES

- Unseasonably hot temperatures will continue to challenge daily records today before noticeable cooling arrives during the middle of the week.

- Isolated showers and potentially a few thunderstorms will remain possible mainly across south-central Arizona through Wednesday.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Yesterday provided even more convective activity across Sonora Mexico while also extending northward into south-central Arizona late in the afternoon and through the evening hours. Moisture was just enough yesterday to provide for scattered showers and thunderstorms across Pima County into southern Maricopa and Pinal Counties. An overall dry boundary layer and high clouds bases provided plenty of DCAPE for gusty outflow winds which spread a good amount of dust northward into the Phoenix area.

A southwesterly low level flow along with storm outflows from Sonora continues to advect moisture northward into our area. The moisture advection will continue in the lower levels through the morning hours boosting surface dew points into the 50s areawide by mid morning. Although, at the same time and through the rest of today, winds will turn more westerly spreading drier air into Arizona. A good amount of sunshine will be seen today allowing for destabilization, but as the drier air mixes down into the boundary layer instability will start to decrease by mid to late afternoon. However, there should still be enough moisture in the low levels for a few isolated showers and thunderstorms during the afternoon and evening hours. Hi-res CAMs are not in good agreement exactly where this activity will occur, but the more favored areas will be across far southern Maricopa County into western Pinal County and also potentially across the higher terrain north and east of the Phoenix area. Today's storm environment will be less conducive to gusty downdraft winds compared to yesterday, but it should be enough to provide for some localized gusty winds of up to around 40 mph.

From Tuesday night through Wednesday morning, a shortwave trough will be quickly moving eastward through the region. This disturbance is expected to contain some system moisture, but barely enough for scattered shower chances focused more across the central Arizona high terrain. We currently have forecast PoPs of 10-15% across the lower deserts of Arizona to 30-45% across the higher terrain north and east of Phoenix. The best time frame for any shower activity looks to be Tuesday night through mid to late Wednesday morning before the disturbance exits to our east by Wednesday afternoon. Any lingering rain chances across the eastern Arizona high terrain Wednesday afternoon should end by sunset. Temperatures will again be quite warm today with highs reaching as high as the upper 90s across southeast California to the mid 90s in the Phoenix area. A noticeable cool down will then take place Tuesday into Wednesday with highs falling back mostly into the mid 80s by Wednesday.

LONG TERM /THURSDAY THROUGH SUNDAY/

The weather pattern will shift once again later this week with upper level troughing setting up across the central U.S. and a ridging building off the West Coast before eventually sliding into our region by the weekend. Dry west northwesterly flow takes over across the Desert Southwest starting Thursday with moisture levels lowering and temperatures initially staying fairly stable as a weather system passes by to our north. NBM forecast highs remain in the mid to upper 80s for Thursday and Friday, but this will not last long as the ridge will be entering our region by Saturday. Fortunately, guidance favors the ridge already weakening as it moves into our region, but it will be enough to push daytime highs back into the low to mid 90s over the weekend.

AVIATION

Updated at 1020Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds will be light and variable with speeds generally aob 5 kt through the majority of the morning. At KIWA and KPHX they may predominately be out of the southeast during the mid-morning hours. Diurnal westerly winds are expected to develop by the late morning/early afternoon. Wind speeds increase up to 7-12 kts in the afternoon with gusts up to 15-20 kts. An outflow is less likely Monday afternoon and no VCSH/VCTS are expected. However, hi-res models are indicating that a complex of storms will develop near Wickenburg late this afternoon and move eastward through the evening. So, we will need to watch if this complex develops later today for a potential northerly outflow boundary moving into the Phoenix Metro. SCT to BKN mid and high clouds will continue to pass over the area.

Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through the TAF period. Winds will remain predominantly southeasterly at KIPL through early this afternoon, followed by a westerly sundowner wind in the late afternoon and evening. Winds at KBLH will mostly fluctuate between SE and SW through Monday with periods of light variability. Winds will then be light this morning and increase up to 7-12 kts, with gusts up to 15-20 kts, in the afternoon at KBLH and evening at KIPL. SCT to BKN mid and high clouds will continue to pass over the area.

FIRE WEATHER

Moisture levels have improved helping to boost humidities and MinRHs to around 20%. The better moisture has also helped to bring back low-end rain chances with a few isolated thunderstorms still possible today across the eastern districts. Isolated rain chances should continue for the eastern districts through Wednesday, but thunderstorm chances will mostly end after today. Outside of any convective induced winds, expect typical spring afternoon upslope gusts 20-25 mph. The near record breaking temperatures will cool slightly by Tuesday and more so starting Wednesday. Rain chances will completely come to an 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%.

CLIMATE

Daily record highs:

Date Phoenix Yuma El Centro ---- ------- ---- --------- 3/30 97 in 2004 99 in 1934 101 in 1934

PSR WATCHES/WARNINGS/ADVISORIES

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