Weather Caution Next Week

[maverick]

Some sites are showing the possibilities of monsoonal flows to be quite strong starting next Wednesday (7/27) thru the weekend. NOAA reports the following:

Anyone with plans next week, especially outdoor plans, should pay attention to the forecast next week as more details on highest chances for thunderstorms and what impacts they may produce come into better detail and confidence.

[michaelzim]

@maverick

I have tried to find your reference below on the NOAA site (and c/o HS Topix "Resources" page) with no luck. Can you direct me to where you get your best long term forecast from - and/or the source for the potentially increased thunderstorms next week.
I check out Weather West for a look into the future weather but there is nothing new posted there since early mid July.

Thanks much ~ Michaelzim

[robow8]

Try this: https://mammothweather.com/

[maverick]

https://forecast.weather.gov/product.ph ... glossary=1

LONG TERM...Sunday and the Work Week.

The highlight of the extended forecast will be the return and expected persistence of monsoonal moisture and storm chances. As previously mentioned, the upper-level high is expected to meander back to the Four-Corners vicinity over the weekend, a favored location for monsoon activity. As this occurs, south-southeasterly winds aloft associated with the anticyclonic flow will advect better moisture into our region. Along and southeast of I-15,
PWATs are expected to exceed 1.25" as early as Sunday. Moisture will continue to remain above normal throughout the week as the southeast flow persists, with PWATs of 1.5"-2.0" possible in the aforementioned areas. Scattered showers and storms are expected each afternoon, with the NBM showing the best chances on Monday.
This coincides with the arrival of an easterly wave reflected in both the GFS and ECMWF ensemble means. With some upper- level support in the forecast, Monday could be a more robust monsoon day in terms of thunderstorm activity.

As the week progresses, guidance indicates that the high could expand into northern Nevada, drawing better moisture to our northwestern areas as well, increasing their precipitation chances. While there remains some details to be ironed out, the overall synoptic pattern appears to be favorable for period of active weather. Beyond the thunderstorm activity, noticeable changes will
be felt in the afternoon temperatures. Highs are expected to fall to seasonal values and possibly a few degrees below normal, an indication of the increased mid-level moisture and monsoon activity.
One could argue that the decrease in temperature is counteracted by the increase in humidity. Indeed, it will likely feel rather muggy, with forecast dewpoints in the middle and upper 50s.

[michaelzim]

@maverick Back-checking your links I found the source points so can get there in future...

Thanks much ~ Michaelzim

[SSSdave]

With my modest Glen Alpine and Hilton Creek backpack trips completed, next week was going to do some photography near Sonora Pass plus Mono Lake, however not now with the Oak Fire active pushing smoke in those directions so today just worked on something further south enough. Now mid week likely to go up Bear Ridge into the ignored Volcanic Knob Recess Peak plateau last visited in 1987, 25 years ago, that looks like a 3 night trip. Sierra National Forest has a new process that reads like I just make the rec dot gov res online, then phone Prather for a night box pick up. Quota and availability for Bear Ridge shows nobody on that trail haha. Sorry folks no named lakes, no fishing so it must not be worthy unless one is a peak bagger. Sentinel Hub shows snows were still on Recess Peak 2 weeks ago and meadows optimal green so likely near this droughty summer's wildflower peak at sub 11k. The rich Volcanic Knob geology soils offer some nice areas. I'll spend a least one late afternoon looking up Bear Creeks upper dogleg canyon towards Seven Gables.

Outside the Washburn and Electra smoke zones, the Sierra air clarity so far for weeks has actually been better than usual due to the atmosphere circulations. That can make for better early and late light with excellent blue day hour skies. Per Maverick's input, Hanford has just backed off on a strong monsoonal flow and now it is less serious to spotty that is more likely better for photos. If anyone (f/m) would like to help carry up some of this scrawny octogenarian's much too heavy gear, PM.

[maverick]

NOAA:

LONG TERM...Monday through Friday.

Monsoonal moisture will be in place through much of the week as the main area of high pressure sets up of the Four Corners region and southerly flow dominates our weather pattern. The chance for thunderstorms with impacts such as heavy rain, flash flooding, lightning, and sudden gusty winds will be possible each day...however exact details on where impacts will set up and to what level they might be is still lower confidence.

Ensembles show high probabilities for over 1" PWATs across much Arizona, southern Nevada, and eastern San Bernardino County for at least the first half of the week. Monday and Tuesday in general might be the time period for the highest and most widespread monsoon impacts as this is when moisture will be the highest at 1-1.5" PWAT for a large area. This is also the time period that things such as EFI, GEFS M-Climate, and ensemble probabilities of 24hr 100-yr QPF return intervals are highlighting as higher potential for extreme precipitation...especially in Mohave County.
EC/GEFS means also hint at an impressive vorticity lobe coming around the anticyclonic flow Monday into Tuesday. If this does develop, this would further increase concerns for higher thunderstorm activity and monsoon impacts.

After Tuesday, ensembles diverge about how much moisture will remain in place over the region. There will likely still be decent moisture available however there is a chance that the highly anomalous PWATs in the place the beginning of the week retreat slightly. GEFS shows this occurring Wednesday while the ECMWF ensemble doesn`t have moisture decrease until Friday. Long range models also differ on the placement of the area of high pressure
and where the best southerly flow that pushes moisture northward will set up. There will probably still be a risk for thunderstorm impacts the second half of the week for at least portions of the region but low confidence on anything more than that.

Temperatures will run a few degrees below normal at the beginning of the week when moisture is the highest and then are expected to rebound back to near normal for the second half of the week.

https://forecast.weather.gov/product.ph ... glossary=1

[SSSdave]

Next week will make a huge difference on how the 2022 late summer season Sierra high country backpacking season rolls out. After a bizarre droughty winter, June and July thunderstorm activity thus far has been minor. Not enough to dent the droughty look:



I've seen some pretty well green late summer conditions after droughty winters if monsoon storms get active. Wunderground dot com is now showing late afternoon storms active 9 straight days with some days storms by late morning. The forecast monsoon flow could provide enough water for green conditions at Sierra Crest zones into September that was otherwise looking like a dry August with many streams withering. For photographers that can also provide some special conditions that are special to experience.



Area Forecast Discussion
National Weather Service Reno NV
144 PM PDT Sat Jul 30 2022

The intense heat of the past few days will transition to a more
stormy pattern Sunday through Tuesday as monsoonal moisture
streams into the region. Storms will favor the eastern Sierra
Sunday, then spread northward Monday and Tuesday. Gusty outflow
winds, lightning and heavy rain are all on the table. Drier air
and typical daytime winds return Wednesday and Thursday for
reduced thunderstorm chances...
These simulations favor the eastern Sierra of Mono/Alpine to Mineral
Counties for the best coverage of storms both days. Given the
moisture content and slow storm motions, stronger storms will be
capable of heavy rainfall, so we will have to keep an eye on
recent burn scars...
TUESDAY: PWAT levels drop into the 0.6-0.9" range as a shortwave
off the west coast begins to move eastward and flow aloft
increases a bit and gets a bit more southwest component. The
increase in mid level winds and a bit less moisture would favor
stronger and more organized storms, possible a few severe storms
with hail and strong outflow winds. Plenty of moisture for those
heavy downpours, so burn scars will remain highly susceptible as
well...
The forecast becomes a bit murky beyond Thursday as
some long range models show the ridge building overhead again
while others keep the door open for a return surge of moisture.
This may be in response on how the models are handling the
remnants of what is now Hurricane Frank, located southwest of
the Baja Peninsula in the east Pacific.

[northwesterner]

Just returned from 4-days Agnew Meadows to Tuolomne Meadows via Donohue Pass Monday evening.

We crossed Donohue at around 10AM Sunday, overcast conditions but no rain. Later in the day further down Lyell Canyon, some on and off rain shows plus thunder.

Monday, we hiked out. Donohue Pass was shrowded in thick clouds all day. Heavy rain on occasion on our hike out and on the trip down Tioga Pass.

Hopefully this series of monsoonal storms brings needed rain and gives us a decent Aug/Sept hiking season we've missed the last two years, though I don't envy anyone trying to cross Donohue today.

[frozenintime]

i'm kind of amazed at the length of this weather window -- we exited the sierra on tuesday 7/26, which was the first day with a chance of thunderstorms. today's 7 day forecast is still predicting 20-50% chances of storms every day through next monday (8/8).

obviously much can change in a forecast that far out, but that's two straight weeks with a chance of storms!