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FXUS65 KPSR 101112 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 410 AM MST Fri May 10 2024

UPDATE
Updated Aviation

SYNOPSIS
A warming temperature trend going through the weekend will result in above normal temperatures and increasing chances of triple digit highs across the lower deserts going into next week. Otherwise, dry conditions will persist, with afternoon breeziness continuing to cause areas of elevated fire weather conditions over the next several days.

DISCUSSION
Early morning satellite depicts few to scattered high clouds spread out across southern Arizona, while water vapor imagery shows a persistent east to west oriented longwave trough entrenched across western CONUS. This trough has been responsible for keeping temperatures at or below normal over the last several days. However, this trough is expected to weaken over the next few days, as anomalously strong ridging that is currently over the Pacific Northwest impinges on this trough. However, negative or neutral height anomalies will continue to persist over the next several days, so while a warming trend will occur, it will mute the absolute maximums of this warming trend to the low 100s at most through early next week.

Ensembles have hedged towards stronger negative height anomalies to persist across the region through the middle of next week, resulting in lower probabilities of 100 degree highs for the Phoenix area to generally a 30-50% range through most of next week. Generally speaking, the warmest day based on the deterministic NBM forecast will be Sunday (Monday) for the western (eastern) districts as the trough weakens during this period before reestablishing its position as the aforementioned ridging flattens out early next week. Winds will continue to be breezy during the afternoon hours as westerly flow persists through this period, resulting in areas of elevated fire weather conditions when combined with the very dry conditions (minimum RH's in the 10-15% range), mainly in higher terrain areas where the gustiness will generally be stronger.

Looking towards late next week, ensembles continue to show potentially more robust ridging building into the Desert Southwest going into next weekend. However, ensembles show considerable spread in regards to a troughing feature that may dig southward across Alberta and Saskatchewan, which could dampen the strength of this ridge. Thus, temperature trends are a bit more uncertain, as chances for highs exceeding 100 degrees seem higher, but should the more robust troughing occur, high temperatures staying below 100 degrees would be a near certainty.

AVIATION
Updated at 1110Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH:

No major weather issues will exist through Saturday morning under only a FEW passing cirrus decks. Wind trends will be very similar to the past several days, though with somewhat less afternoon gustiness (only around 15kt). Periods of variable winds will also be common, especially during times of wind shifts and the late night/early morning hours.

FIRE WEATHER
Temperatures are expected to warm over the next several days, with chances for highs reaching 100 degrees increasing above 50%, at least for the western districts, by late this weekend. Temperatures are expected to remain above normal going through early next week.
MinRHs will be in the 5-10% across the lower deserts and in the 10- 15% range across the higher terrain through this weekend. Overnight recovery will be poor in the 20-40% through tonight, before improved recoveries in the 30-60% range heading into early next week. Typical springtime breeziness continues through the weekend with afternoon and early evening wind gusts of 20-25 mph. These breezy conditions combined with dry fine fuels, and low RHs will likely create some elevated fire weather conditions. Dry conditions persist into next week.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...None.
CA...None.

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