Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 180924

Area Forecast Discussion
National Weather Service Grand Junction CO
324 AM MDT Fri May 18 2018

.SHORT TERM...(Today through Saturday)
Issued at 302 AM MDT Fri May 18 2018

The low to our west has now become an open wave though some weak
mid-level circulation continues to persist at this hour as seen on
satellite. Today, all convective parameters indicate a chance for
some convection this afternoon. Lapse rates are in the 9 to 10 deg
C/km range while LIs range from -1 to -3 for the most part. Some
CAPE is also available this afternoon. The disturbance moving
overhead will also provide some lift and get things going so a few
showers and storms look a safe bet. Models continue to highlight
the northern valleys and Continental Divide as the best chances
for any convection so forecast follows suit and also included the
San Juans, eastern Uintas, and Book Cliffs for a chance as well.
The atmosphere remains quite dry so don`t expect much in the way
of any QPF from storms. In this environment, better chances for
some gusty outflow winds. Expect cumulus to start forming from
about 10AM onwards as very short range models show showers/storms
getting going between noon and 1PM. Those areas not seeing showers
will also likely see some cumulus clouds this afternoon, generally
over higher terrain. The increased clouds should keep high
temperatures slightly cooler than seen yesterday...a few degrees
or three.

Saturday looks to remain unsettled as an area of low pressure over
the Front Range manages to draw in some moisture and bring it into
our CWA. If this occurs, the northern mountains, and to a lesser
extent the central mountains, will see some precipitation with
the higher elevations seeing a bit of snow. This precip will start
around noon with increased coverage mid-afternoon onwards before
quickly dwindling to nothing by midnight. The NAM and GFS both
show this solution while the EC wants to keep the precip on
Denver and Pueblo`s side of the Rockies. Hoping the EC is wrong
and followed the NAM/GFS guidance. Like today, those areas not
seeing any rain will see some clouds in the afternoon. Northerly
flow will also bring high temperatures right around normal for
this time of year.

.LONG TERM...(Saturday night through Thursday)
Issued at 302 AM MDT Fri May 18 2018

Unsettled conditions are expected through Monday with scattered
mountain convection and isolated valley activity. Pattern dries
back out Tuesday as deep southerly flow develops across Eastern Utah
and Western Colorado ahead of another deepening low pressure
system that settles into the western Great Basin late Tuesday and
Wednesday. Would anticipate fire weather concerns to elevate a bit
in this pattern with gradients tightening and humidity values
likely dropping. The EC is not quite in sync with the GFS and
offers a wetter solution later in the week. Will be leaning a bit
more toward the GFS solution as it did a bit better with the last
low that sat nearly stationary to our west for several days.

Temperatures will be running near seasonal normals through Monday
with an expected bump up Tuesday through Thursday.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 302 AM MDT Fri May 18 2018

A few showers and storms will form this afternoon and evening but
will remain over the northern valleys and northern mountains. KHDN
may see experience one of these showers/storms this afternoon and
evening while remaining TAF sites should remain clear of any
convection. VFR will continue to prevail at all airfields. The
showers and storms that do form will likely cause some gusty
outflow winds across the CWA.



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