Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 222327

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
427 PM MST Mon Jan 22 2018

.SHORT TERM...(Tonight through Tuesday night)
Issued at 240 PM MST Mon Jan 22 2018

Temperatures across the region were much colder this morning than
guidance and have been slower to warm as expected thanks to
developing inversions due to recent snow cover. Expect this trend
to continue through mid-week as a lighter northwest flow remains
overhead, with not much mixing occurring. Satellite is already
showing some clouds entering northeast Utah and northwest
Colorado from the west as a weak shortwave moves through this
northwest flow. This shortwave will clip the northern Colorado
mountains this evening through Tuesday morning, lending itself to
a couple inches of snow at the higher peaks in the realm of 2 to 4
inches. Otherwise, expect dry conditions elsewhere through
Tuesday night. Some patchy fog developed in a few valleys last
night and expect the same again the next few nights due to the
ever present snow cover, keeping the lower levels more saturated.
Due to inversions, lowered high and low temperatures through
Tuesday night to slow the warming trend and kept to persistence
with some slight moderation through the week.

.LONG TERM...(Wednesday through Monday)
Issued at 240 PM MST Mon Jan 22 2018

A ridge of high pressure will slide overhead Wednesday with the
flow shifting to westerly. Still expect the continued presence of
valley inversions so reduced temperatures through Wednesday night
once again, resulting in cooler temps than guidance. By Thursday,
an upper level trough accompanied by a 100 kt jet will move into
the northern Great Basin from the west. This will tighten the
pressure gradient over the region with the flow switching to
southwest as H7 winds increase to the 40 to 50 kt range Thursday
afternoon and evening. Thinking this increased mid and upper level
flow will be enough to break any valley inversions, resulting in a
breezy to windy day and sufficient mixing. This mixing will also
allow afternoon temperatures to warm quite a bit. Increased winds
during this period to show this trend.

Regarding this storm system set to impact the region Thursday
evening into Friday, the latest forecast models have been
trending further north over the last few days and continue this
trend today. What does this mean? Well, the northern and central
mountains still look favored for snowfall with the south becoming
mostly dry. The cold front looks to move through Friday morning,
bringing colder air in the realm of -12C to -16C. It should be
noted that the GFS is the driest solution, showing the northern
mountains seeing the best snowfall in the prefrontal southwest
flow Thursday evening and with the cold front through Friday
morning with decent moisture, as specific humidity values range
from 2 to 2.5 g/kg with the front. Behind the front, there is
significant drying which is concerning, as specific humidity
values drop to 1 to 2 g/kg over the divide mountains and less than
1 g/kg over valleys. This is not boding well for significant snow
or widespread precipitation for that matter. The ECMWF is a
little further south towards the central mountains and wetter,
with snow hanging on in northwest flow through Saturday morning.
The Canadian is somewhere in between the two. Regardless,
confidence is lower for significant snow with this system having
seen the trend towards a further north and drier solution in the
past few days of model runs in both the GFS and ECMWF. Ridge of
high pressure builds back into the region by the weekend into
early next week, for dry conditions and a return to near or above
seasonal temperatures.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 427 PM MST Mon Jan 22 2018

A weak disturbance moving across northwest Colorado will bring
snow showers to the Elkhead and Park Ranges. CIGS at KHDN are
expected to lower below ILS breakpoints for periods between 07Z
and 20Z. Elsewhere, expect VFR conditions, CIGS above ILS
breakpoints and light winds through the next 24 hours.






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