Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 191741

Area Forecast Discussion
National Weather Service Grand Junction CO
1141 AM MDT Thu Apr 19 2018

Issued at 948 AM MDT Thu Apr 19 2018

Forecast models have been consistent over the past several runs in
both the track and timing of the closed low moving through
eastern Utah and western Colorado over the next 48 hours. The low
is expected to arrive in southern Utah late this evening with a
nice tap of moisture streaming in from the south. This impressive
moisture feed will kick off showers over the San Juan Mountains
and, though snow levels will remain high, periods of heavy snow
will fall at elevations above 10kft. As the low tracks east into
the Four Corners overnight into Friday, showers will increase in
coverage. The presence of a significant TROWAL signature will
allow for good wraparound moisture as the storm continues to
progress into eastern Colorado. Favorable easterly, northeasterly,
and eventually northerly flow will fuel orographic snowfall over
the northern and central mountains through early Saturday. Given
projected snowfall amounts and the abundance of moisture available
with this storm, went ahead and issued various winter weather
highlights for the Eastern Uinta Mountains as well as the
northern, central and southern mountains along the Continental
Divide. Accounting for the initial tap of southerly moisture at
the onset of the storm, the San Juans, West Elk and Sawatch
Mountains were put in a Winter Storm Warning while ranges further
north were left in Winter Weather Advisories for now. However, if
some heavier snow bands develop, these Advisories may have to be
upgraded later on, but will just have to wait and see how
things play out for now. The onset of the highlights were
staggered to account for the progression of the low across the


.SHORT TERM...(Today through Friday)
Issued at 310 AM MDT Thu Apr 19 2018

A strong Pacific storm was moving into the Western Great Basin
early this morning and will move steadily east through the day.
The primary initial consequence of the approaching storm will be
steadily increasing winds starting about 9-10 AM this morning.
Wind speeds should reach a peak along the CO and UT border between
6 and 8 PM today. Models indicate moisture being drawn north from
NM this evening with an associated increase in precipitation
chances along the Continental Divide. The precip is well ahead of
the low center in the warm advection portion of the storm. Models
historically over predict this warm advection precipitation, but
have been consistent with it in the last few runs.

On Friday the upper low center is projected to travel from central
UT over SW and central CO. A trowal signature should help wrap
precipitation around the northern and western quadrants of the
storm Friday. This will shift the main focus of precipitation to
the northern third of western CO and eastern UT. The cold
advection will reach the forecast area which will lower snow

.LONG TERM...(Friday night through Wednesday)
Issued at 310 AM MDT Thu Apr 19 2018

By late Friday afternoon and into the evening hours this cyclone
will have fully tapped into the meat of the warm conveyor belt fed
by GoMex moisture. Theta transport vectors and humidity profiles
are showing the classic T-Bone steak pattern developing with the
left branch of the WCB arcing back into NE.Utah and NW.Colorado
Friday night. This area of moisture advection and dynamics from
the storm should lead to heavier precipitation potential in our
northern CWA through the early morning hours before the storm
refocuses on the Front Range and the Plains for Saturday. This
precip will occur during the coldest part of the storm and at night
so accumulations during this time could be the most impactful for
travel. Residual wrap around mositure will keep some shower
activity around for Saturday on our side of the hills with the
better chances right near the divide through sunset. Transitory
ridging sets up early Sunday into early Monday ahead of the next
Pacific trough aiming for the N.Rockies. This is just a brush by
but a cool front looks to sag into the northern CWA and may add
just enough lift to squeeze out some light precipitation across
the divide peaks going into Tuesday morning. The upstream system
pushing this storm through is 180 degrees out of phase along the
Left Coast by Wednesday leaving confidence well below par. As for
temperatures...Saturday may be a bit below normal but we should
warm to above normal for much of the extended forecast and mirrors
the CPC outlooks.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1140 AM MDT Thu Apr 19 2018

VFR conditions are expected to prevail through the afternoon.
Winds will become gusty out of the southwest at all terminals.
Cloud cover will increase and thicken through the afternoon. Any
shower activity will hold off until after 9pm with the chance of
some rain showers begining first in TEX, ASE, and HDN. Expect
deteriorating ceiling heights overnight and into Friday morning.


Issued at 932 AM MDT Thu Apr 19 2018

Red Flag Warnings remain in effect today for most of Colorado as
gusty winds move back in along with dry humidities. Winds will
begin increasing after about 9 AM in many locations and continue
well into the evening. When Red Flag Warnings are in effect open
burning is highly discouraged as any fire starts will be difficult,
if not impossible, to control.


CO...Winter Storm Warning from 9 PM this evening to 6 AM MDT Saturday
     for COZ018-019.

     Red Flag Warning until 9 PM MDT this evening for COZ200-202-203-

     Winter Storm Warning from midnight tonight to 6 AM MDT Saturday
     for COZ012.

     Winter Weather Advisory from midnight tonight to 6 AM MDT
     Saturday for COZ004-010-013.

UT...Winter Weather Advisory from 6 AM Friday to 6 AM MDT Saturday
     for UTZ023.



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