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Area forecast discussion 
National Weather Service Grand Junction Colorado
411 am MDT Sat Aug 30 2014

Short term...(today through sunday)
issued at 405 am MDT Sat Aug 30 2014

As a weak ridge passes east of the area this morning...a trough
will move from the West Coast inland and into the Great Basin this
afternoon. A weak jet will spread over the area ahead of the
troughline...along with a few small vorticity maxes. These will provide
some lift this afternoon...but moisture is down significantly as
the 00z precipitable water was only 0.60 inches. Forecast soundings add some
moisture this afternoon with predicted precipitable water rising above 0.70
inches and cape in the 300 to 600 joule range. So with a little
dynamic lift...a bit of speed shear aloft...and the middle levels
moistening a little as well...believe isolated to low-end scattered
probability of precipitation are still a good bet for this afternoon...with the best probability of precipitation
from the bookcliffs north. Overall...maximum temperatures should rise another
5 degrees or so across the area.

Tonight and Sunday...a large open trough will be swinging across the
western states over the next 48 hours on it/S way to the Great Lakes
region for early next week. This Pacific jet will be rounding the
base of this trough overnight and help provide large scale ascent to
the northern 2/3 of our County Warning Area. Moisture will be on the increase
according to precipitable waters ...pushing back to near 0.75 or near normal for
late August. However profiles most of this moisture limited to the
middle an upper levels of the sounding. NAM continues to be the more
aggressive solution with a sharper cyclonic curve to the jet over
western Colorado tonight...however the solution is tamer than 24
hours ago. The GFS/Euro keep a broader curve to the jet and the
better forcing remains north. Implications in the NAM solution
include precipitation spreading across the northern valleys to the
central mountains...while the other solutions favor the northern
mountains more wind than rain likely in northern valleys.
Confidence not high but did lean toward the latter solutions and
ended precipitation quicker and kept the higher probability of precipitation well to the
north. Temperatures also tricky as the upper dynamics in the NAM
are strong enough to force a front and cooler air into our central
County Warning Area. The GFS and especially the Euro keep the front well to the
north. A blend of guidance still used for highs as there is as
much as 10 degree spread in places.

Long term...(sunday night through friday)
issued at 405 am MDT Sat Aug 30 2014

Sunday night into Monday...dry northerly flow sets up over the west
as the trough pushes into the eastern plains on Monday. The drier
air and clear skies will drop temperatures Sunday
night...especially in the northern valleys. High temperatures on
Monday will stay near or slightly below normal in the weak cold air advection on
the back side of the trough. However these should be short lived
as zonal to broad southwest flow will be setting up for the
remainder of the week as low pressure reforms to the west.

Monday through Friday...the broad trough over the northern rockies
and High Plains will continue moving east Monday with moderate
northwest flow aloft over the forecast area. Tuesday and Wednesday
the flow aloft relaxes as high pressure becomes centered over Arizona
and nm...ushering warm and dry conditions. On Thursday a trough
begins to move onshore over the Pacific northwest and the
southern ridge begins to slide east...allowing the winds aloft to
shift to southwesterly as the western trough approaches. Dry
southwest flow remains over the area Friday as the western trough
stalls over the pacnw and western Great Basin.


Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 405 am MDT Sat Aug 30 2014

VFR conditions will prevail at all taf sites today and tonight.
With low areal coverage showers possible this afternoon and
evening...Montana tops will be locally obscured with storms producing
erratic wind gusts to 40 miles per hour. The chance of this storms degrading
flight conditions at any of the taf sites is very low.


Gjt watches/warnings/advisories...


long term...15

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