Area Forecast Discussion

KEY MESSAGES

* Late October system brings valley rain/mountain snow to region Friday, Saturday, and Sunday

* The strongest part of the system moves through on Sunday will bring small snowfall accumulations to valleys; higher amounts to area peaks and ridges

* The region dries out early next week

DISCUSSION

(Today through next Friday)

WEATHER PATTERN OVERVIEW:

Large and complex upper level trough of low pressure is on track for its approach to the silver state. Models are still showing a complex upper level setup consisting of a large parent longwave trough that will stretch along the entire west coast. Making up the trough trough are up to three local maximums in vorticity. Today through Sunday, the main trough will slowly push in, with three vorticity maximums. One off the coast of Washington, a second off the southern California channel Islands, and a third in the middle off of the SF Bay area. Models runs are consistently showing the northern segment lifting into Canada. With the middle vorticity max becoming the dominant area of lift, developing a broad yet closed low as it moves over Nevada. The southern trough segment now looks to become absorbed by the dominant trough segment/closed low as it to moves inland. Another factor with this trough will be a stream of tropical mid level associated with tropical storm Vance that is lifting north ahead of this trough, while assisting with enhancing moisture associated with this system will also provide instability for shower development for Friday and Halloween, before the main system moves overhead Sunday. Model timing has continued to show this more consistently with a 35% to 70% chance for isolated to scattered showers, as well as a few thunderstorms, possible Friday and Saturday. Chances increase to near 100% Sunday through Monday morning as the core of forecasted upper low moves over Nevada. Current multi-day precipitation amounts have continued to trend higher as well given the slightly slower movement, but increased organization of the upper system with passes and valleys seeing rain amounts of 0.10 for the Black Rock desert to 0.65 for Elko, Ely, and mid- elevation passes. While higher elevation passes and mountain ranges seeing between up to 0.65 to 1.50+ of water or water equivalent (for snowfall). Snow levels will again start high at 9000 feet, dropping to about 7000 feet by Sunday. With a trace to 0.5 possible for the higher elevation passes passes of US-50 and NV 225, and up to 1 foot of snow for the range peaks. Monday afternoon high pressure will build in as the trough departs bringing quieter weather back into the region this ridge will be in place at least through Wednesday. Model agreement breaks down after Wednesday as models show another trough moving over the great basin, or continued upper level ridging over the southwestern US. Temperatures, thanks to the active pattern will be relatively consistent over the weekend and into next week as highs will be near to, to slightly below normal ranging in the upper 40s to upper 50s, with lows in the mid 20s to upper 30s.

FORECAST CONFIDENCE & DEVIATIONS: There is high confidence for the potential for several rounds of scattered showers and thunderstorms starting late Thursday afternoon, and persisting on and off through early Monday morning.

There is high confidence in the return of upper ridging Monday afternoon through at least Tuesday of next week which will bring quiet, dry conditions for the region.

There is low confidence for the upper level pattern after Wednesday of next week, as models show conflicting solutions for the end of next week.

AVIATION

VFR conditions look to be the primary flight conditions through Saturday morning. Upper level system will bring a 35% to 70% chance for isolated to scattered showers and a few isolated thunderstorms for Nevada Terminals for Friday and Saturday, with higher chances Sunday. Winds will shift ahead of this system to the south to SW at 5KT to 15KT with gusts up to 25KT possible.

FIRE WEATHER

Fire Weather conditions will be low next several days for all zones. A large upper level storm system is expected to move across the west coast through Monday morning. Several rounds of isolated to scattered rain showers, a few thunderstorms, and mountain snowfall will be possible. Friday and Saturday will have a 35% to 70% chance for showers, and a few storms. While Sunday chances increase to near 100%. Winds look remain on the breezy side out of the S to SW at similar speeds of 10 to 20 MPH with gusts up to 30 MPH possible.

LKN Watches/Warnings/Advisories

None.