Area forecast discussion
National Weather Service Grand Junction Colorado
432 am MDT Sat may 25 2013
Short term...(today through sunday)
issued at 430 am MDT Sat may 25 2013
Colorado and Utah will be under moderate southwest flow aloft today as low
pressure remains stationary over the Pacific northwest. Conditions will
be warm and dry...with winds just strong for fire weather
concerns. Over southwest Colorado the fuels remain dry and today winds
and low humidity will produce red flag conditions at lower
elevations. Temperatures will average about 5 degrees above normal
across the forecast area. A weak vorticity maximum passing over the
Colorado/UT/WY triple point will produce some middle and hi cloud this
morning but these will move north and east of the area by noon.
Tonight and Sunday...winds will diminish this evening after sunset
as the atmosphere decouples with the loss of heating.
Energy will continue to rotate around the Pacific northwest low on Sunday and
maintain dry southwest flow across the forecast area. Models show an
upstream Pacific disturbance digging farther south into northwest Nevada
by Sunday afternoon...while a shortwave trough in the southern
stream enters Southern California. High clouds will increase Sunday afternoon
as the nose of a weak upper jet moves in from the southwest. Daytime
heating will again provide a gusty characteristic to the afternoon
winds. Warmer than normal temperatures continue.
Long term...(sunday night through friday)
issued at 430 am MDT Sat may 25 2013
Sunday night and Monday...the Southern California disturbance will move
across the 4 corners toward midday on Monday. The shortwave
disturbance that moves into Nevada late Sunday will lift across southern
Idaho/western Wyoming on Monday as it rotates around the upper low still
located over the Pacific northwest. These should bring a bit more clouds
to the area on Monday and in turn a few degrees of cooling...but
no precipitation.
Monday through Friday...the trough along the West Coast will begin
moving inland Monday. The upper winds over the forecast area will
become more southerly Monday and Monday night. By sunrise Tuesday the
negative tilt trough will be over the Great Basin with increasing
middle and hi cloud spreading over eastern Utah and western Colorado. The
remains of a weak surface front is projected to move through the
forecast area late Tuesday afternoon and Tuesday evening. With the
increasing high moisture and greater instability...dry
thunderstorms will be a possibility Tuesday afternoon and evening.
The surface front should be east of the forecast area by Wednesday
morning with northwest flow and a better chance of precipitation
Tuesday night and Wednesday. Western flow will develop over the area Wednesday
afternoon and Thursday as the polar jet rides just south of The
Four Corners. Drier air with northwest flow will spread across the area
Thursday night and Friday.
&&
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 430 am MDT Sat may 25 2013
VFR conditions will continue across the area today and tonight.
Gusty southwest winds at the surface and aloft will produce areas
of mechanical turbulence over the ridges from late this morning
until about midnight tonight.
&&
Fire weather...
issued at 430 am MDT Sat may 25 2013
Dry and warm southwest flow directed at eastern Utah and western
Colorado will lead to red flag conditions this afternoon/evening in
Colorado zones 207 and 291 where fuels are critical. The critical fire
weather conditions will ease after sunset tonight as winds diminish.
Will issue a Fire Weather Watch for these same zones...207 and
291...for Sunday afternoon for low humidity...gusty winds...and a
Haines index of 6. Gust strength will be dependent in part on the
amount and thickness of high clouds Sunday afternoon...as surface
heating and the resultant mixing will be the primary generators of
the gusts. Confident that localized red flag conditions for these
zones will be observed Sunday...but still some question as to
whether wind gusts in excess of 25 miles per hour will become widespread.
Hence... the Fire Weather Watch and will give the day shift a chance
to re-evaluate later guidance...and also see how today turns out.
As the larger-scale western trough begins to move inland next
week....an increase in the winds and high/middle level moisture may
lead to more fire weather issues including dry thunderstorm activity
about Tuesday. Cooler conditions are expected after Wednesday.
&&
Gjt watches/warnings/advisories...
Colorado...red flag warning from noon today to 9 PM MDT this evening for
coz207-291.
Fire Weather Watch from Sunday afternoon through Sunday evening
for coz207-291.
Utah...none.
&&
$$
Short term...cc/jad
long term...cc/jad
aviation...cirrocumulus
fire weather...cc/jad
