Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 150551

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1151 PM MDT Wed Mar 14 2018

Issued at 1151 PM MDT Wed Mar 14 2018

Updated the forecast for rest of tonight to include at least
isolated thunderstorms through the early morning hours as
thunderstorm activity still ongoing across northeast Utah and into
portions of northwest Colorado. Increased PoPs in this area as
well through the night. Also, updated our forecast low tonight as
guidance coming in warmer than forecast and current temps in the
60s still across much of the lower valleys. With persistent cloud
cover, thinking the lows will stay quite mild so nudged towards
warmer guidance.

The last thing updated was the snowfall forecast, lowering overall
amounts and keeping the best accumulating snow above 10,000 feet.
Due to the warm advective and convective nature of this system
through Thursday night, thinking the snow levels will be varying
largely with this system as convection helps drive snow levels
lower in some areas, while other areas remain elevated. Models
also have a tough time resolving this convection and trying to
pinpoint which areas will see the best accumulations, which
overall tends to be overdone. The reasons described above should
limit overall accumulations due to the scattered nature of the
convection as this feels more like a spring storm than a late
winter event. Thunderstorm activity looks to pick up again
Thursday afternoon after a brief downturn overnight in terms of
lightning activity.

UPDATE Issued at 904 PM MDT Wed Mar 14 2018

Updated the forecasts as isolated thunderstorms and scattered to
numerous showers developed over the Utah Grand Flat and the Roan
and Bookcliffs Plateaus early this evening. This should persist
and continue moving to the NNE through midnight.


.SHORT TERM...(Tonight through Thursday night)
Issued at 345 PM MDT Wed Mar 14 2018

Current storm system moving through the Great Basin this afternoon will
start to impact the forecast area this evening across
northeastern Utah and the remainder of the area by tomorrow
morning. Very warm conditions in southwest flow are occurring
ahead of this system today. Expect shower activity with some
isolated thunderstorms to develop this evening and increase as
colder air filters into the area overnight. 700 mb temperatures
around 4C this afternoon will drop to near -3C by tomorrow
morning. With these warm temperatures expect mainly rain below
10kft this evening but snow levels will quickly fall to near
7500ft by tomorrow morning. As the colder air moves into the
region, expect fairly unstable conditions to develop with
forecasted lapse rates of 8 to 9 degrees C/km on Thursday. This
instability will allow convection to develop during the day on
Thursday and have added slight chance/chance of thunderstorm
mention. Expect mainly sub-advisory impacts across the mountains,
however, with the convective nature of this system, localized
higher amounts are possible where convective showers and
thunderstorms do develop. Temperatures on Thursday afternoon will
run 15 to 20 degrees colder than today.

.LONG TERM...(Friday through Wednesday)
Issued at 354 PM MDT Wed Mar 14 2018

Snow shower activity will diminish Thursday night as system moves
east of the area with the best focus across the northern and
central mountains of western Colorado. The next system on its
heels will move across CA/OR border by late Friday. As this system
moves into the Great Basin Friday night through Saturday,
southwest gradient winds will increase across the region. Showers
and possible a few thunderstorms will develop late Saturday and
Saturday night with lower valley rain and higher valley/mountain
snow continuing into Sunday. Light to moderate snowfall
accumulations across the mountain locations with the best focus
across the northern and central mountains is expected. A
shortwave ridge will move through the area on Monday and Tuesday
with dry conditions ahead of the next storm system which should
impact the area by midweek. This system currently looks like it
will draw from a more subtropical fetch of warm moist flow with
potential impacts for the latter half of the workweek.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1047 PM MDT Wed Mar 14 2018

A broad trough will spread scattered showers and a few
thunderstorms over northeast Utah and northwest Colorado east and
over all of western Colorado by sunrise. Mountains will become
obscured. Over most TAF sites CIGS will remain above ILS
breakpoints, but CIGS will approach ILS breakpoints over KVEL.
ktex and kdro through the period.




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