textproduct: NWS Phoenix

KEY MESSAGES

- Major waterways such as the Salt and Gila rivers will continue to experience high volumes flows through at least the the weekend due to dam releases.

- With the exception of a slight chances of mountain showers on Friday, dry weather will be common through at least the middle of next week.

- Temperatures a few degrees below normal will warm very close to seasonal readings by the weekend.

SHORT TERM /Today through Saturday/

A compact cyclonic circulation was situated over central Colorado early this morning with an omega block pattern over the Conus breaking down as southern stream jet energy forces a more progressive flow pattern. Weak, elongated troughs will moves across the Conus the next several days before another blocking type pattern develops over the weekend. Part of this evolution will include shortwave energy becoming disassociated with the progressive flow over the SW Conus dragging a weak cold core into northern Mexico and forming a partial cutoff while ridging amplifies over the Great Basin through the weekend. The passage of shortwave energy and increased synoptic ascent Friday may be sufficient to squeeze out a few showers over mountains of central and eastern Arizona, though moisture availability will be extremely limited resulting in only very low chances for light showers. Otherwise, the sharp anti- cyclonic flow behind the trough passage late Friday into Saturday will promote strong surface pressure rises over the Great Basin yielding gusty north winds across the western CWA. H5 heights in a 575-579dm range prior to trough passage will support temperatures around 4F below normal, followed by midlevel height rises and warming of the lower troposphere over the weekend with reading rebounding close to daily normals.

LONG TERM /Sunday through Wednesday/

Some variation of a Rex or omega block will define the southern stream flow pattern early next week as broad ridging dominates the northern Conus and northern stream jet energy retreats into southern Canada. While there are certainly differences among ensemble members regarding the exact placement and intensity of quasi-cutoff features in the southern stream, this synoptic pattern will promote surface pressure rises over the intermountain West and dry N/NE boundary layer flow. As a result, periods of breezy east winds are likely at times over the eastern CWA (very common occurrence this time of year), though speeds should not be particularly strong or unusual. At some point early next week, most ensemble members suggest the aforementioned cutoff feature opening and residual energy moving through the region, though it remains to be seen whether an introduction of mid/upper level moisture can overcome the dry boundary layer airmass. The greatest odds and large preponderance of ensemble membership indicate dry weather persisting through the middle of the week. Forecast confidence is very good that H5 heights will remain nearly constant in a 580-584dm range resulting in a near persistence temperature forecast with readings very near climatology.

AVIATION

Updated at 0520Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns are expected through the forecast period under mostly clear skies until FEW-SCT high clouds moving in tomorrow afternoon. Winds will remain light (generally 7 kts or less) and tend to follow typical diurnal patterns. Confidence in a westerly shift tomorrow afternoon is low. Winds will likely be light and variable, but may tend to exhibit a W/NW component. Winds will then redevelop an easterly component for the overnight hours.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns are expected through the forecast period under mostly clear skies until FEW-SCT high clouds arrive tomorrow morning. Winds will remain light, generally 7 kts or less. Wind directions at KBLH and KIPL will generally remain N-NW. Extended periods of calm and variable conditions can also be expected.

FIRE WEATHER

An isolated shower may affect mountains of eastern districts Friday, albeit with little chance of wetting rainfall while the remainder of the region remains dry through at least the middle of next week. Minimum afternoon humidity levels will largely fall into a 20-30% range in western districts and 30-50% in eastern districts. This will follow fair to good overnight recovery in western districts and good to excellent levels in eastern districts. 20-30 mph northerly gusts will be common in western districts Friday night through Saturday, while a period of enhances easterly winds will develop over eastern districts early next week. Outside of these time frames, winds will be very light with little to no gustiness.

PSR WATCHES/WARNINGS/ADVISORIES

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