Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 131637

Area Forecast Discussion
National Weather Service Denver/Boulder CO
937 AM MST Fri Jan 13 2017

Issued at 927 AM MST Fri Jan 13 2017

Considerable high level moisture continues to stream in from the
Southwest from the upper low over Southern California. Low level
moisture not all that deep in the mountains so will just continue
scattered snow showers with only minimal accumulations. Much of
the widespread snowfall remains over Western Colorado. Still
dealing low clouds and patchy fog on the plains. This has been
slow to dissipate due to the higher cloud cover. Will delay some
of this clearing. No other changes needed.


.SHORT TERM...(Today and tonight)
Issued at 159 AM MST Fri Jan 13 2017

Light snow continuing in the mountains at this time, but
the HRRR shows a steady decrease through this morning as mid
level warm air advection develops. Will keep snow in the grids for
the today and tonight but chc pops for the most part with little
if any accumulations over the next 24 hours. The flow aloft will
remain southwesterly with nearly neutral mid level qg over
northern Colorado through tonight. The next system along the
central CA coast at 12z today will continue to move southward into
Baja MX by 12z Saturday, so minimal upper level support for any
pcpn through that time. As for the northeast plains of Colorado,
low stratus clouds around this morning with a low potential for
fog as well. Will keep patchy fog in the grids for early this
morning. As for the rest of the day, surface high pressure will
weaken today with generally light and variable winds. Temperatures
today a little cooler than normal with varying amounts of high
cloudiness in the 500-300 mb layer moving over the region ahead of
the developing storm system over southern California.

.LONG TERM...(Saturday through Thursday)
Issued at 159 AM MST Fri Jan 13 2017

The upper level low that will affect the region will move across
the Baja Peninsula Saturday and across northern Mexico Saturday
night. A south-southwest flow aloft will prevail over Colorado.
Mid and high clouds ahead of this storms system is expected to
keep temperatures near normal. Just a slight chance for
precipitation Saturday and Saturday night over the southern parts
of the area. Low levels start to moisten up early Sunday morning
which could produce drizzle/freezing drizzle over the eastern

May see snow spread west into the Denver area Sunday afternoon as a
southeast flow around the low increases moisture over the area.
Precipitation type over the eastern plains still uncertain at this
time. The GFS soundings show it will be warm enough for rain at
Limon Sunday. Slightly cooler temperatures at the surface would lead
to freezing rain and slight cooling of the lower airmass would
result in snow.

Models have trended a little slower and west with this system over
the past 24 hours making precipitation a little more likely. Best
snow for the area looks to be late Sunday night and Monday. Since
the heaviest precipitation is still 2 to 3 days away and the track
is still uncertain, will hold off from issuing any Winter Storm
Watches at this time. If this system continues to slow, most of the
impacts may not occur until Monday. The GFS still indicates less
than a tenth inch of precipitation will occur in Denver while the
ECMWF continues to show over a half inch. The easterly turn the GFS
shows on Monday, doesn`t make much sense with a ridge over the
eastern U.S. The south to north track the ECMWF shows for Monday
appears more reasonable.

The storm system is expected to be east of the area Monday night. A
dry northwest flow aloft will prevail behind it on Tuesday.
Temperatures will be near normal. Flow aloft turns westerly
Wednesday. A trough moving onto the west coast will cause flow aloft
to back to the southwest for Thursday. Expect snow to return to the
mountains Wednesday or Wednesday night. The snow should continue
into Thursday. With the airmass originating over the Pacific,
temperatures should be mild. Windy conditions will be possible
across the foothills and eastern plains.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 927 AM MST Fri Jan 13 2017

Still dealing with IFR conditions at local terminals though BJC
has just improved recently. With the higher clouds overhead,
clearing has been slower than anticipated. Will make some minor
adjustments in the low cloud clearing. Winds will be light and
variable today.




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