Marine Weather and Tide Forecast for Floriston, CA

DISCUSSION

Our week is starting off nicely, with a dominant upper level ridge providing a mild and partly cloudy Sunday. This pleasant fall pattern is set to continue right through Veterans Day. The main story for the first half of the week will be the warmth, as this building ridge will cause temperatures to keep climbing, peaking on Monday with a strong possibility of setting new high temperature records. The existing 74-degree record at the Reno-Tahoe International Airport has a 70% chance of being broken outright and an 80% chance of at least being tied. This stable airmass will also keep winds light and terrain-driven and allow for valley inversions to develop overnight.

All good things must come to an end, and this quiet pattern is no exception. A significant shift is on tap for the middle of the week as our "big bubble, no trouble" of high pressure finally erodes. An upper-level trough is forecast to dig southward from the Gulf of Alaska, approaching the West Coast late Tuesday into Wednesday. As this trough moves in, you'll notice the change: skies will become mostly cloudy on Wednesday, temperatures will begin a minor drop, and breezy conditions will pick up during the afternoon.

This storm shows the potential for strong winds, with the main event for winds currently looking to be Wednesday night into Thursday.
However, the ultimate intensity and placement of these winds are highly conditional on the final depth and track of the incoming trough. This key uncertainty is why the placement of the tightened pressure gradient keeps shifting in the models. Dynamically, the ingredients are there: ensembles consistently place a strong jet streak over the Sierra, positioning the Sierra Front in the right exit region of the jet, a specific area that is favorable for downward momentum transport. A deeper trough would support a stronger jet and a more efficient transfer of 50-70 kt 700 hPa winds down to the surface. Because this evolution is still uncertain, current NBM guidance shows a 40-60% probability for wind gusts to exceed 45 mph late Wednesday into Thursday, impacting Sierra valleys, the Sierra Front, and portions of far Western Nevada.

Another big uncertainty with this trough is its depth - that is, how cold will it be? This will be the deciding factor for snow levels and potential accumulations. Ensembles continue to waver on this, and as it stands, the potential snow level for Donner Summit has a pretty big range from as low as 3000 feet to as high as 7000 feet.
This is the key detail we will be refining in the coming days. We are also tracking a healthy plume of moisture, which is consistently forecast to be aimed at the Sierra. The orientation of this plume suggests that the heaviest precipitation will likely fall west and along the Sierra crest, with modest spillover into western Nevada.

While it is 3+ days out and these details will change, the current probabilistic outlook for the main storm period (Wednesday evening through Friday) gives us a first look at potential totals. For Sierra passes like Donner and Echo Summits, there is an 80-85% chance of over 1 inch of rain, a 60-65% chance of over 2 inches, and a 25-30% chance of over 3 inches. For snowfall in those same locations, there is a 65-75% chance of over 6 inches, a 35-55% chance of over a foot, and a 10-20% chance of over 18 inches. For Western Nevada cities like Reno and Carson City, the probabilities for rainfall are 50-70% for over 0.50 inches, 30-55% for over 0.75 inches, and a 15-35% probability of over an inch.

The consistent signal for a pattern change is clear, and those in the region should use the calm first half of the week to prepare for potential impacts from strong winds, valley rain, and Sierra snow late Wednesday through Friday.

-Johnston

AVIATION

VFR conditions will prevail across all terminals today and Monday under light, terrain-driven surface winds and scattered cirrus.

The main exception will be at KTRK tonight into Monday morning.
While a strong inversion will be in place, dew point depressions are forecast to remain around 2-4 degrees overnight, which is typically unfavorable for widespread FZFG (15% probability), but some patchy FZFG or BR are possible. This may cause brief MVFR to IFR conditions from 06Z-16Z Monday.

Aviators should enjoy these quiet VFR conditions, as a pattern change is forecast to bring stronger winds and precipitation to the region mid-to-late week.

-Johnston

REV Watches/Warnings/Advisories
NV...None.
CA...None.