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Recognizing Incoming Bad Weather Before It Happens

Discussion related to Sierra Nevada current and forecast conditions, as well as general precautions and safety information. Trail conditions, fire/smoke reports, mosquito reports, weather and snow conditions, stream crossing information, and more.
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Recognizing Incoming Bad Weather Before It Happens

Postby maverick » Wed Feb 13, 2013 4:00 pm

Are you familiar with the signs below? Everyone heading out into the outdoors should
be. Those of you who have been backpacking, fishing, or mountaineering for years
(decades), have you ever changed you itinerary because of an incoming system which
you could foresee by any of the below signs (or a combination of them)?
Have you seen some of the below signals, did not head there warning(s) and later got
hit by a system that was scheduled to hit a few days later?
Personally my eyes are constantly watching the skies for all the signs mother nature
gives me, especially in the transitional months like October, or if there is anything
predicted to move into the area a few days after my scheduled exit, surprises can
happen and we all know weather forecasts are not always 100% correct.
We should all know these signs and act on them appropriately to ensure our safety
while in the backcountry.

Signs of approaching bad weather (within 24 to 48 hours) may include:

- A gradual lowering of the clouds. This may be the arrival or formation of new
lower strata of clouds. It can also indicate the formation of a thunderhead.
- An increasing halo around the sun or the moon.
- An increase in humidity and temperature.
- Cirrus clouds.
- A decrease in barometric pressure (registered as a gain in elevation on an altimeter).

The approach of a storm system is indicated when:

- A thin veil of cirrus clouds spreads over the sky, thickening and lowering until
altostratus clouds are formed. The same trend is shown at night when a halo forms
around the moon and then darkens until only the glow of the moon is visible. When
there is no moon, cirrus clouds only dim the stars, but altostratus clouds completely
hide them.
- Low clouds, which have been persistent on lower slopes, begin to rise at the time
upper clouds appear.
- Various layers of clouds move in at different heights and become abundant.
- Lenticular clouds accompanying strong winds lose their streamlined shape, and other
cloud types appear in increasing amounts.
- A change in the direction of the wind is accompanied by a rapid rise in temperature
not caused by solar radiation. This may also indicate a warm, damp period.
- A light green haze is observed shortly after sunrise in mountain regions above the
HST= Wilderness Adventurer who knows no bounds, except for their own imagination.

Have a safer backcountry experience by using the HST ReConn Form 2.0, named after Larry Conn, a HST member:

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Re: Recognizing Incoming Bad Weather Before It Happens

Postby cherron » Wed Feb 13, 2013 8:39 pm

Good a class I took they shortened it to "lowering, darkening, thickening" of cloud formations - just to make it easier to remember.
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Re: Recognizing Incoming Bad Weather Before It Happens

Postby acvdmlac » Thu May 09, 2013 7:40 pm

There is also truth to the old adage "red at night, sailor's delight; red in the morning, sailors take warning." The meteorology is a bit complex but I've seen it bear out repeatedly in the Sierra and elsewhere.
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Re: Recognizing Incoming Bad Weather Before It Happens

Postby tallkan » Wed Nov 05, 2014 11:48 am

I too find the "sailor's delight" addage useful. However, the only caveat I would add to this reference is that sailors were mostly concerned with wind patterns. Often, a cold rainy day would not be seen as "bad weather" to a sailor as long as wind patterns were favorable. I've seen red in the evening and then experienced a cold drizzly day, but with low wind, which might not be ideal, but at least it's not dangerous conditions. So still very useful!!
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