textproduct: NWS Phoenix

KEY MESSAGES

- Strong high pressure will quickly build into the region over the next few days leading to drying conditions and near record temperatures by the weekend.

- An even stronger high pressure system is expected to move 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 Heat Risk next week.

SHORT TERM /TODAY THROUGH FRIDAY/

Forecast concern into next week is solely on the record warmth expected for mid March. The weather system that brought rainfall on Monday is now fully removed from the region, while a record strength high pressure ridge has developed off the coast of southern California and northern Baja. The weather pattern is favorable for much of the warmth from this ridge to quickly move into our region over the next few days. H5 heights over our area have already increased to between 578-582dm, or into the 90th percentile of climatology, while the center of the ridge is as high as 590dm.

As the ridge fully moves into our region today into Thursday, we will experience rapid warming and drying throughout the atmospheric column under clear skies. Surface temperatures will lag a bit due to only fair mixing, but today's highs should easily reach into the low to mid 80s followed by 90-95 degrees already on Thursday. Daily records may also be in jeopardy as early as Thursday, but more so by Friday as the NBM shows highs 92-95 degrees in the Phoenix area to 94-97 degrees across the western deserts. As the boundary layer dries out, diurnal temperature ranges will become quite large allowing overnight lows to still dip into the low to mid 50s for rural desert areas to the upper 50s to low 60s elsewhere.

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 0505Z.

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 window of VRB to calm conditions, especially overnight and during directional changes. Other than a FEW high clouds over the region tonight, skies should be mostly clear.

Southeast California/Southwest Arizona including KIPL and KBLH: The only aviation concern over the next 24 hours will be FG potential at KIPL. As of now, too much uncertainty exists to include a prevailing or even TEMPO group for reduced VIS at the terminal, therefore, only VCFG is mentioned in the TAF at this time. Updates may be needed if direct VIS impacts are realized. Otherwise, both terminals will experience light winds with extended periods of VRB to calm conditions and just a FEW passing high clouds early tonight.

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.