textproduct: NWS Phoenix

KEY MESSAGES

- Well above normal temperatures will continue into early next week, with lower desert highs reaching the lower to middle eighties, resulting in areas of Minor Heat Risk.

- A pattern change next week will cool temperatures somewhat and may eventually bring rain chances to portions of the forecast area late week into the following weekend.

SHORT TERM /TODAY THROUGH SATURDAY/

Broad anticyclonic flow stretches from the Eastern Pacific all the way through the Central CONUS, with a couple embedded upper level disturbances, one decaying system moving northward over the Great Basin and another off the SoCal coast closing off from the northern stream as it dives south southeastward. Ensembles remain in excellent agreement that the closed low off SoCal will settle far south of the region, off the Central/Southern Baja Coast by Saturday before it progresses eastward into Mexico late this weekend into early next week. With the closed low remaining distant to our south, positive midlevel height anomalies will stay entrenched over the Desert Southwest. Anticipate temperatures to continue in an 8F-12F above normal range today and Saturday as a result. This translates to afternoon highs in the lower 80s for many of the typically warmer lower desert locales, and overnight lows ranging from the middle 40s to middle 50s. Be sure to stay hydrated and take breaks in the shade if you are attending outdoor events today or over the weekend, especially visitors from out of state that are unaccustomed to temperatures this warm during the winter.

LONG TERM /SUNDAY THROUGH THURSDAY/

The overall pattern becomes more progressive this weekend into next week, with longwave troughing over the Eastern CONUS finally shifting over the Atlantic, broad ridging over the Western US sliding eastward, and a more unsettled pattern developing along the West Coast. Sunday and Monday are shaping to be a few degrees warmer than Saturday, as the closed low remains far to our south and the axis of the Western US ridge moves directly overhead, maximizing subsident motion over our area. Probabilistic NBM shows very narrow spread in forecast highs through Monday, yielding excellent confidence in temperatures peaking around 12F-14F above normal, in the middle 80s for some of the warmest spots.

During the middle of next week, a more distinct pattern shift occurs over the region, as flow aloft shifts from easterly/northerly to west/southwesterly ahead of a shortwave trough digging south along the West Coast. Spread increases in forecast highs, reflecting uncertainty in the impact of cloud cover and proximity of negative height anomalies associated with this incoming trough. However, temperatures should remain in an above normal category, likely reaching the middle to upper 70s for highs across the lower deserts Tuesday through Thursday. Upper level forcing and better quality moisture do not align to bring rain chances to the forecast area until late in the week, when most ensembles agree the trough will sweep through the Southwest US. This will bear watching over the next few days, but confidence is currently low on this initial shortwave bringing much precipitation due to its short residence time, warming aloft (indicating weakening), and positively tilted axis as it moves onshore. A much stronger trough diving south over the East Pacific during the middle of the month (next weekend) looks more promising for rain chances across the forecast area, so stay tuned as details become more clear.

AVIATION

Updated at 0500Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns this TAF period with passing high clouds. Overall light and variable winds with slight diurnal tendencies.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns this TAF period with a few high clouds. Winds light and variable with an overall northwesterly component at KBLH.

FIRE WEATHER

Well above normal temperatures and dry conditions will continue into early next week. Afternoon MinRHs will range from 15-25% areawide through Monday, with overnight recoveries generally in a 35-60% range. Winds will remain light, generally below 15 mph through Monday, with a northerly fetch this weekend then becoming southwesterly Monday afternoon. A pattern change during the middle of the upcoming week will cool temperatures several degrees, though they will remain above normal, increase humidities slightly, and bring periods of increased breeziness. Rain chances do not enter the forecast until late next week, where CWR over the high terrain of the eastern districts increases to 15-25%, however, confidence is still low on timing and forecast rain totals this far out.

PSR WATCHES/WARNINGS/ADVISORIES

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