Area forecast discussion
National Weather Service Las Vegas Nevada
946 am PDT Sat may 25 2013
Synopsis...a dry southwest flow will persist over the region
through Memorial Day. Locally breezy to windy conditions will
develop each afternoon with temperatures slightly below normal. A
low pressure system is expected to move into Nevada Tuesday bringing
a chance of showers and thunderstorms and much cooler temperatures
to the region.
&&
Update...a broad trough over the western states will continue
through the Holiday weekend and into early next week. A series of
disturbances will brush across northern Nevada today and again
Sunday...before trough digs into the southern Great Basin on
Tuesday. A dry southwest flow will persist through Monday leading to
breezy to locally windy conditions. Believe a red flag warning is
not justified across Mohave County today but will monitor winds
closely just in case. Conditions looks very similar for Sunday so at
this time do not anticipate any new products being issued.
Did adjust sky and wind grids some with the morning update.
&&
Aviation...for McCarran...southwest winds 13-20kts through the
afternoon hours with gusts around 25kts. Few-scattered high clouds at or above 25k
feet. Similar winds expected on Sunday but likely a knots or two
lighter.
For the rest of southern Nevada...northwest Arizona...and southeast
California...south to southwest winds 12-18 kts the rest of the
morning then increasing to 15-25kts by middle day. Stronger gusts of 30
to 35kts are possible in the vicinity of kigm and across the
northwest plateau of Mohave County. Winds will be similar on Sunday
but marginally weaker by a couple kts. Scattered high clouds at or above 25k feet
at times.
&&
Previous discussion...
250 am PDT Sat may 25 2013
Short term...today through Monday night...the low pressure system
which has been over the Pacific northwest the past several days will
continue over the region through Sunday before lifting to the
northeast late Sunday. Another low is then forecast to drop south on
Memorial Day and move into the County Warning Area late Monday night. The short
range models are coming more inline with this second system...but
the European model (ecmwf) continues to be a little slower and deeper than the
GFS/NAM. Thus have trended towards a compromise for the Monday night
period. The result is that continued dry southwest flow will remain
over the region today through much of Memorial Day...before
increasing clouds are seen Monday night County Warning Area wide with a chance of
showers over the southern Sierra by Tuesday morning.
The main concern during the short term will continue to be breezy to
windy southwest winds during the afternoons and early evenings
across much of the region. The strongest winds are likely to be seen
across Mohave County and the extreme western portion of the Mojave
Desert with fire weather concerns being the main impact. However
will need to monitor the winds as local gusts may reach into
advisory levels on Sunday and Monday afternoon.
Daytime temperatures will continue to be 3 to 5 degrees below normal
through the period.
Long term...Tuesday through Friday...the 00z European model (ecmwf) trended weaker
than the previous run with energy moving into the Great Basin
Tuesday while the GFS remained progressive and dry. In
response...associated parameters were adjusted to account for the
weaker...more progressive European model (ecmwf) solution. Temperatures were raised
slightly...probability of precipitation were lowered across mainly the southern County Warning Area with
adjustments to timing and precipitation location made further north. Quantitative precipitation forecast
amounts were kept light based on limited available moisture and the
progressive nature of the system. Models bring more shortwave energy
across northern Nevada Wednesday which could increase winds and
result in a few showers across the north. The European model (ecmwf) maintains a
northwest flow across the region Thursday and Friday with additional
vorticity energy moving through the area. The GFS and Gem are more zonal
with impacts limited to areas well north of the area.
&&
Fire weather...the Pacific low pressure area which has been over
the Pacific northwest for the past several days will continue over
the area through Sunday. This will continue to result in breezy
to locally windy conditions during the afternoon/early evenings
across the district. Local red flag conditions will likely be
seen...especially across Mohave County Arizona and the western
portion of the Mojave Desert and will need to monitor for winds
becoming more widespread than current thinking. In addition very dry
conditions will continue with minimum relative humidity values
lowering to below 10 percent across much of the district each
afternoon...with only poor recoveries overnight...especially in the
lower deserts.
A change is expected to take place on Tuesday however as another low
pressure area begins to drop south and across the region. This
system is expected to bring cooler temperatures to the district
along with a slight chance of showers/possible thunderstorms to the
mountains Tuesday afternoon...while local gusty winds will continue
to be seen.
&&
Vef watches/warnings/advisories...
Nevada...none.
Arizona...none.
California...none.
&&
$$
Update...Pierce
aviation...czyzyk
previous discussion...Jensen/Salmen
For more forecast information...see US on our webpage:
Http://weather.Gov/lasvegas or follow US on facebook and twitter
