National Weather Service Forecast Discussion

			

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fxus65 krev 161000
afdrev

area forecast discussion
national weather service reno nv
300 am pdt tue mar 16 2010

.short term...

upper ridge will remain over the great basin today...with a
shortwave trough moving into the pac nw later this afternoon. as
this shortwave pushes into wa/or...it will help to increase
southwest flow over our forecast area this afternoon. along with the
very warm temperatures aloft already in place...currently 36 degrees
at the top of slide mountain...should see some very good
mixing/warming this afternoon. lower valleys in western nevada will
see well above normal temperatures today and wednesday...about 10-12
degrees above the norm for mid-march. that means mid to upper 60s
in the lower valleys...with mid to upper 50s in the sierra.

as we go into wednesday...700mb flow will weaken as the shortwave
pushes into the northern rockies and the flat ridge builds back in
temporarily. thermal trough will develop over the sierra...causing
some local convergence and lift over the higher elevations. lifted
index values are hitting some really impressive numbers for
march...between -2 to -3c in the sierra...with cape values
approaching 500 j/kg. nam/gfs were hinting at the potential
yesterday...but with the latest trends will increase up to chance
pops and add thunder to the forecast especially given the well above
normal temperatures for march.

ridge strengthens off the west coast on wednesday night...which will
open up the great basin to a shortwave/cold front on thursday. as
the front pushes down into the area...should see another round of
showers thursday afternoon along the boundary. north flow behind the
front will drop temperatures down 5-10 degrees...from what we saw
tue-wed.  hoon

.long term...friday through monday...

confidence is a bit lower tngt with the gfs showing more spread with
amt of cold air assocd with nely flow at beginning of fcst and most
models are now backing off on syst late in pd.

nly flow on back side of upr low wl result in cooler and very dry
ams fri-sat. the ecmwf maintained consistency with its further ewd
track than the deterministic gfs. taking a look at sref plumes for
850-700mb thickness...there are definitely two camps with regard to
amt of cold air with one much warmer than the other. this is
reflected in the most recent mos ensemble guid which shows a range
from mid-upr 50s to mid-upr 60s acrs wrn nv vlys. no middle ground
for the gfs. decided to lean more twd the consistent ecmwf and
warmer members of the gfs but did cool readings a couple of degrees
to account for the other possibility. confidence is only moderate.
on the other hand there is very good agreement and high confidence
in the very dry airmass. dewpoints were decreased further with
single digit and teens to be common.

for sun and mon...models have trended more progressive and flatter
with s/w energy with a drier and somewhat weaker nwly flow. did not
make too many changes and kept a slgt chc of showers nrn zns for mon
and a general incr in sfc-rdg lvl winds. temps should remain abv
normal with 50s sierra and 60s wrn vlys. confidence is only moderate
for this latter half of pd. hohmann
&&

.aviation...

vfr with light winds. for ktrk...brief reduction in vsby from local
shallow fog possible thru 14z although probability of vsby or cigs
below instrument landing mins is only about 10 percent. hohmann
&&


.rev watches/warnings/advisories...
nv...none.
ca...none.
&&

$$

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