textproduct: NWS Phoenix

KEY MESSAGES

- Strong high pressure will quickly build over the region during the next couple of days leading to dry conditions and rapid warming with near record temperatures by the end of the week.

- An even stronger high pressure system will build over the region next week, likely pushing daily highs into the triple digits across the lower deserts while breaking daily and potentially monthly high temperature records.

- Widespread Minor Heat Risk is expected through the weekend before increasing to Moderate HeatRisk next week.

SHORT TERM /TODAY THROUGH FRIDAY/

The latest objective analysis shows high pressure aloft quickly building across the region from the eastern Pacific with 500 mb height fields already approaching 585dm under generally clear skies. This will lead to rapidly warming temperatures through the end of the week. Afternoon high temperatures today will generally top out in the low to mid 80s and will be the transition of what is expected to be a prolonged stretch of record warmth. By Thursday and Friday, as 850 mb temperatures rise to around 20C and under clear skies, afternoon highs will heat up into the low to mid 90s across most of the lower desert communities, which will be a solid 15 degrees above normal for mid-March. Daily record highs will be challenged, especially on Friday, when all climate sites (Phoenix, Yuma, and El Centro) have a greater than 75% chance of breaking the record.

LONG TERM /SATURDAY THROUGH NEXT WEEK/

Record temperatures are likely for this weekend and through much, if not all of next week as model guidance shows remarkable agreement in the long term. The warming trend at least looks to stall out over the weekend as a trough passes by well to our northeast and a weak disturbance attempts to break through the ridge from the west. However, this disturbance will become cut off from the main flow by Sunday, before retrograding westward early next week. Temperatures this weekend may even dip a couple degrees on Saturday before starting to warm again into early next week. Forecast highs over the weekend are still between 10-15 degrees above normals with most lower desert locations topping out in the lower 90s to as warm as the mid 90s across the western deserts of southwest Arizona and southeast California.

Another even stronger high pressure ridge will develop Sunday into Monday off the West Coast before quickly moving directly over our region by next Tuesday. Ensemble H5 heights are shown rising to 583-586dm by Monday, or around the 97th percentile of climatology, before peaking at around 590dm mid to late next week. Although it is still nearly a week away, guidance agrees this will result in record strong heights and temperatures over our region for several days next week. High temperatures will respond quickly with readings nearing 100 degrees across the western deserts on Monday and likely reaching or topping 100 degrees for most lower desert locations by next Tuesday or Wednesday. NBM probabilities of breaking daily record highs surges to around 90% by Tuesday and near 100% for next Wednesday-Friday. Most of the lower deserts are forecast to reach between 100-105 degrees from Tuesday through Friday of next week, or 20-25 degrees above normal. Phoenix is nearly certain to see its earliest 100 degree day ever as the earliest ever was on March 26, 1988.

Widespread Moderate HeatRisk is expected to develop by next Tuesday and last through at least next Friday. NBM 75th percentile guidance (25% probability) also shows potential for highs nearing 110 degrees late next week, which would be unprecedented even for April, let alone March. The earliest ever 106 degree high in Phoenix is May 2, while Yuma and El Centro have never reached 107 degrees before May. If these temperatures are realized, we could have areas of Major HeatRisk late next week.

AVIATION

Updated at 1725Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will follow familiar light and diurnal trends with periods of VRB to calm conditions, especially overnight and during directional changes. Mostly clear skies will continue.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected during the TAF period. Current light and variable conditions will continue into the afternoon at KBLH and through most of the evening at KIPL. This afternoon winds at KBLH will go NE'rly then NW'rly later tonight, with speeds aob 7 kt. Late this evening winds will go W'rly at KIPL, with speeds remaining aob 5 kt. Mostly clear skies will also continue.

FIRE WEATHER

Dry weather with unusually warm temperatures and low humidities will return during the latter half of the week with record setting warmth likely by the weekend. Minimum humidity levels in a 20-30% range this afternoon will deteriorate significantly closer to a 7-15% range late in the week. Correspondingly, good to excellent overnight recovery will retreat into a 20-40% poor to fair category. Winds will be fairly light with only modest afternoon upslope gustiness limiting a greater fire weather danger.

PSR WATCHES/WARNINGS/ADVISORIES

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