Area Forecast Discussion
Issued by NWS Grand Junction, CO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
FXUS65 KGJT 162349

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
549 PM MDT Tue May 16 2017

Updated aviation section

.SHORT TERM...(Tonight through Wednesday night)
Issued at 333 PM MDT Tue May 16 2017

The closed low responsible for the showers and storms this
afternoon and evening has opened up and become an open wave as it
moves across the CWA. The strongest storms remain over the Front
Range underneath the strongest divergence aloft. Enjoy the spring
temperatures today because everything comes to a screeching halt
as the next system moves in.

A strong 110+kt jet streak continues to drop down from just off
the British Columbia coast supporting a very deep, closed low.
This low and associated cold front will be moving across our CWA
early tomorrow morning and will have pushed through by early
Thursday morning. As the front moves through, we can expect some
heavy rain and showers, gusty winds, and a few rumbles of
thunder. Higher elevations will see a rain or rain/snow mix to
start but temps will drop rapidly once the front moves through so
a switchover to all snow will occur quickly. Cross sections do
show some very strong omega (lift) as the front moves which
indicates some impressive snowfall rates possible for the
mountains Wednesday afternoon. Winter weather advisories remain in
effect for all mountains with generally 6 to 12 inches of new
snow with a few spots seeing higher amounts.

.LONG TERM...(Thursday through Tuesday)
Issued at 333 PM MDT Tue May 16 2017

By Thursday morning, the front will be well to our east while the
cold, upper level low slowly moves overhead. These types of lows
typically bring isolated, but heavy and sporadic, rain and snow
showers to the area and this low will be no different. The 12Z run
showed a large, pronounced lull as the upper low moved overhead
with wraparound flow bringing plenty of snow to Pueblo and
Denver`s forecast area while we stayed mostly dry. The 18Z run now
brings in more moisture to our CWA though seems a bit overdone as
winds generally remain easterly favoring the mountains of the
Front Range. However, the advisories remain in effect through
Friday so capture this possibility well.

How cold is it going to get? High temperatures may top out a good
20 to 30 degrees cooler than we`ve seen recently. It will be a
brisk Thursday morning across the entire CWA. Latest guidance
suggesting many areas will be hovering around freezing but after
looking at average freeze dates and record freeze dates, many
valleys still right where they should be for this time of year.
Freeze watches continue for those areas that may see the largest

By Saturday, precipitation finally ends but this break will be
short lived as another weak, open wave approaches from the
northwest bringing a return to showery precipitation Sunday
afternoon through Tuesday. Under this flow, the northern half of
the CWA looks favored for precipitation including the central and
northern mountains with some more snow possible for those areas,
especially the Park and Gore Ranges, thanks to favorable

As far as temperatures are concerned, they will rebound Saturday
onwards reaching more normal values by Tuesday.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 549 PM MDT Tue May 16 2017

Unsettled pattern continues over the next 24 hours.. with some
isolated showers tonight and gusty winds through 03z or 04z
tonight. A break is expected overnight before showers increase in
coverage between 15z and 18z Wednesday with an unseasonably cold
front moves into the region. Rain in the valleys and snow in the
mountains will allow conditions at terminal to degrade throughout
the day. ILS breakpoints will likely be reached across all TAF
sites starting between 18z and 22z with MVFR possible during this
time and thereafter closer to 00z.


CO...Freeze Watch from late Wednesday night through Thursday morning
     for COZ006-007-011-020-021.

     Winter Weather Advisory from 6 AM Wednesday to 6 PM MDT Friday
     for COZ004-009-010-012-013-017>019.

UT...Freeze Watch from late Wednesday night through Thursday morning
     for UTZ024.

     Winter Weather Advisory from midnight tonight to 6 PM MDT Friday
     for UTZ023.



AVIATION...JAM is the U.S. government's official web portal to all federal, state and local government web resources and services.