Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Junction Colorado
335 PM MST Sat Dec 3 2016

Short term...(tonight through Sunday night)
issued at 335 PM MST Sat Dec 3 2016

Dendritic temperatures near mountain top and weak upslope and
afternoon instability is leading to very light snowfall over much
of the central and northern mountains this afternoon. There will
be a decreasing trend this evening with flurries hanging around
the northern Divide past midnight. Another cold night in store
with cloud cover limited to thin high cirrus. The cold air will be
organizing north of the Continental U.S. Border on Sunday while a quiet day
is expected here tomorrow. Mid level temperatures will be warming
some and develop a weak inversion. This translates to warmer
temperatures along the mid slopes while the valleys may struggle
and kept the lower guidance forecast in place below 7000 feet. The
pattern across the western Continental U.S. Will then begin to buckle Sunday
night as high latitude energy and cold air will be diving
southward following the jet digging into the Desert Southwest.
Much of the upper level moisture will be wrung out upstream and
the better forcing stays across the northern rockies but westerly
orographics should provide for some light snow across the northern
Utah and Colorado mountains overnight. Meanwhile an approaching
Arctic front and stronger instability will be just moving to our
doorstep by sunrise.

Long term...(monday through saturday)
issued at 335 PM MST Sat Dec 3 2016

Bigger changes begin on Monday...especially across the northern
County Warning Area. The Arctic front will slowly ooze icy air across the Wyoming
border by mid morning with the faster westerly flow aloft helping
to hold it at Bay. However still a difficult forecast as some
areas in the extreme north will see high temperatures early in
the day then falling through the afternoon. Ahead of this front
mixing will lead to the warmest day of this forecast. Again the
front will provide lift into the mid level unstable layer which
will keep some snow around during the day. Snow ratios will be
increasing meaning lighter...fluffier and better accumulating
snow which will mainly be directed at The Flat Top...park and
northern Gore ranges through early Tuesday. A trailing wave
passing through the flow will again re-excite the front on Tuesday
with mid level lapse rates likely to add another convective punch
to the precipitation. This wave and convection will help push the
Arctic front farther south and it should pass I-70 in the
afternoon. Overall expect snow to be falling over large majority
of the region during this time and expect travel delays. Low
water content snow also means it take much wind for blowing and
drifting to occur. The bigger story however will be the plunging
temperatures as this airmass will have had an open tap to the
North Pole. Light snow is likely to linger into at least Wednesday
with light accumulations. Temperatures will struggle to hit double
digits in the high country while the lower valleys stay in the
20s. We are looking at temperatures some 20 to 25 degrees colder
than normal and lows and looking at double digit lows below zero
in many of the high valleys and basins. The pattern luckily does
stay progressive so this bitter cold air should be swept out with
another passing storm arriving late next week. Temperatures
however will be staying below normal so that means the
precipitation that is falling will be snow.


Aviation...(for the 00z tafs through 00z Sunday afternoon)
issued at 335 PM MST Sat Dec 3 2016

VFR conditions are prevailing at the forecast terminals this
afternoon. Orographic snow is falling over much of the northern
and central mountains leaving widespread terrain obscuration and
lower flight conditions. A passing shower may impact the kase
terminal in this flow but only temporarily during the first part
of this forecast before clearing takes place overnight. The next
24 hours will generally be quiet as VFR dominates. The next
system is organizing upstream and will bring deteriorating
conditions and prolonged periods of lower cigs and precipitation
early next week.


Gjt watches/warnings/advisories...


Short term...15
long term...15

National Weather Service Glossary of Abbreviations