textproduct: Reno

KEY MESSAGES

* Dry and warm conditions today across the region, with a downward trend in temperatures starting Friday.

* Increasing gusts on Friday and Saturday lead to elevated to near critical fire conditions for northeast CA and northwest NV.

* Isolated shower and thunderstorm potential returns for the NV Basin and Range, and south of US-50 Friday into the weekend.

DISCUSSION

One last day of warm temperatures to get through before we see cooler daytime highs roll into town. The inbound trough will help to modify the airmass toward a more seasonally average temperature regime. While we will still hover above August averages, we will say goodbye to the near 100 degree valleys and 90s across the Sierra valleys.

The trough will also be responsible for increasing winds, beginning Friday when afternoon gusts will approach 30 mph. Then for Saturday, gusts of 35-40 mph will be felt by northeastern California and northwestern Nevada as the trough and associated tighter gradient draws nearer. When coupled with the low relative humidity readings anticipated for Friday and Saturday, we expect elevated to isolated areas of critical fire weather conditions both days, with emphasis on Saturday prompting a Fire Weather Watch. See details on this product below in the Fire Weather portion of this discussion.

The other feature that will become part of our weather story this weekend is the persistent ridge over the Four Corners that will allow for a southerly flow to draw monsoonal moisture back into the southern Sierra and southern Basin and Range areas. PWAT values will range 0.6-0.8 inches, which usually spells showers and storms for the area. The limiting factor for convection may be the limited CAPE values of 100-500 J/kg, the higher end being more favorable. This should translate to isolated shower and storm behavior, although some recent CAMs are highlighting a potential for showers to develop over Mineral/Churchill/Pershing counties, then progressively move to the northeast with potential for developing outflows that may reach speeds to 40 mph. Another feature became noticeable today that looks to be some remnants of a tropical wave that is gliding westward along the Mexico border. Will this feature be drawn into the southern extent of our County Warning Area? We are watching... HRICH

AVIATION

* High based clouds across the region signal the arrival of an inbound trough that will linger into the weekend. Today will see gusts of 20 kts at area terminals between 21z-04z, with VFR conditions. Friday, gusts increase over the same time frame to around 30 kts, then on Saturday another increase up to 35 kts.

* Showers and storms may impact KMMH/KHTH/KBAN Friday and Saturday. Chances on Friday of up to 5%, increasing to 10-20% for Saturday. HRICH

FIRE WEATHER

* Elevated fire risk for Friday with an increase of west to southwesterly winds to around 30 mph and min RH around 12-20% for portions of eastern Lassen, the Surprise Valley and northern Washoe counties. Conditions deteriorate to critical by Saturday over the same area with gusts to 30-35 mph with a 10-50% chance of exceeding 40 mph on Saturday, and similar min RH compared to Friday. Critical conditions are expected to last for 3-6 hours between Saturday afternoon and early evening. For these reasons, we are adding headlines to our fire weather products for Friday and have issued a Fire Weather Watch from 11 AM through 11 PM Saturday for northern Washoe and eastern Lassen counties, and Surprise Valley in Modoc County.

-HC/HRICH

REV Watches/Warnings/Advisories

NV...Fire Weather Watch from Saturday morning through Saturday evening NVZ458.

CA...Fire Weather Watch from Saturday morning through Saturday evening CAZ270-278.