Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 290530
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1130 PM MDT Tue Mar 28 2017

.SHORT TERM...(Tonight through Wednesday night)
Issued at 355 PM MDT Tue Mar 28 2017

Deep upper low will meander slowly eastward overnight across
central and southern New Mexico. As this lows wobbles away, deep
north to northeasterly flow sets up shop across the forecast area,
already evident in latest radar returns with showers heading
southwest. Bulk of the heaviest snow has ended for most of our
mountains and with northeasterly flow setting up, potential for
significant snow will be diminished over just about the entire
forecast area. Of course there are exceptions to that rule such as
the north slopes of the Eastern Uinta Mountains and the La Sal
Mountains in eastern Utah and along the northern slopes of the
San Juans, especially areas such as the Uncompahgre Gorge and in
the town of Ouray. Northerly flow looks too strong to get a decent
gorge event going and the moisture will be eroding away from the
eastern Uinta`s rather quickly this evening, with GOES imagery
showing dry air marching steadily eastward this afternoon. With
some reserved hesitation, dropped all of the eastern Utah
mountains for the winter weather advisories (reserved as we could
see another 2 to 4 inches in the La Sals this evening, but impact
on travel is minimal due). The southwest San Juans were also
dropped with only scattered snow showers expected through tonight
with winds more downslope and drying in on the southern slopes.

That leaves us with the central mountains and northwest San Juans
in western Colorado with highlights through tonight. Heaviest
snowfall accumulations will remain at or above the 9k level,
although some accumulations snow will fall down to as low as 6k
overnight as colder air rolls back in. Current highlights for
these area will remain in effect for another 3 to 6 inches of snow
focusing on north and northeast facing slopes. Elsewhere, it`s the
scattered rain and snow showers through this evening, before
things shut down late tonight as we stabilize.

Also expected to see breezy to windy conditions this evening
across southeast Utah into the Four Corners region, including
Cortez as gradient tightens significantly at the 700 mb level.
Strongest winds are expected to remain aloft as inversions set in,
but any showers could drive down gusts in the 40 to 50 mph range.
With loss of heating, bulk of showers will be dissipating and
momentum lost, so no plans on wind highlights at this time.

After tonight, the upper low will be kicking out across the Texas
Panhandle and arriving over the Central Plains states by Wednesday
night. Expect lingering showers early Wednesday with low scud
clouds hanging around and some patchy fog in the valleys,
especially those that see late clearing and received moisture over
the past 24 hours. Temperatures will be running near to a few
degrees above seasonal norms through this period.

.LONG TERM...(Thursday through Tuesday)
Issued at 355 PM MDT Tue Mar 28 2017

The active and progressive pattern will be sticking around for
several more days. Flat, transitory ridge works east on Thursday,
driving temps upwards into the 5 to 10 degrees above normal range.
This warming looks short-lived as another deepening low drives
southeast into the Great Basin Thursday night and Friday. This
system looks more and more interesting by the day as the low
closes and moves slowly into the Four Corners area by Friday and
Friday night. GFS ensembles in fairly good agreement with subtle
shifts in placement ranging from near Cortez to near by Saturday
morning. The Euro and Canadian models are following similar
tracks and all would suggest that we will see another round of
heavy mountains snow with a mixed back of valley precipitation.

Significant cooling also expected to arrive overnight Thursday
through Friday with 700 mb temperatures dropping from +6 to as
low as -10C by Saturday morning over the San Juans. Expected deep
southerly flow ahead of the digging low will drive limited
moisture northeast across the area with some showers expected over
the San Juans after midnight Thursday. Snow levels start off high
again, but will drop as the colder air works through. Southern
valleys from Cortez to Durango and Pagosa Springs will again be on
the cusp of potentially seeing several inches of wet snow, but
leaning toward more of a rain event once again as the coldest air
doesn`t arrive over the southern valleys until after the deepest
moisture has shifted out and the flow has shifted to the north and
northeast, which is not all that favorable for significant
precipitation south of the San Juans. One area that could do quite
well on the back side of this low will be northwest San Juans,
specifically the Uncompahgre Gorge just south of Ouray as weaker
700 mb flow anticipated with the upper low more north of the
system currently impacting the area.

The Eastern Uintas and La Sals are also showing promise for
potentially heavy snowfall with this second system between Friday
and Saturday morning. Most of our remaining mountain zones will
see decent snowfall, but best chances for heavier accumulations
will be across the San Juans, eastern Uintas and the La Sals,
which are all highly depended on how this low sets up and just
where it stalls or slows down.

The one big missing ingredient for this entire system will be a
deep source of moisture as we aren`t tapping much in the way of
additional or add-on juice to the storm. So efficiency is the key
to making this next round exciting.

This low exits late Saturday with Sunday and Sunday night coming
in dry with another ridge rolling through ahead of yet another
wave that is coming across open, which tends to favor our northern
and central mountains. More on that system later.

Temperatures will be jumping around, typical of spring-time in the
Rockies and when put all together, will probably average out to
around normal for this time of year.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1130 PM MDT Tue Mar 28 2017

This storm system will begin to gain momentum eastward during the
early morning hours. Moist upslope into TEX should continue
however until after sunrise with improving conditions there not
expected until at least 29/15Z. ILS conditions are likely to
persist at KASE into sunrise as well. Otherwise VFR conditions
will dominate the forecast at the remaining forecast terminals.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until noon MDT Wednesday for COZ009-010-
     012-013-018.

UT...None.
&&

$$

SHORT TERM...JDC
LONG TERM...JDC
AVIATION...TGJT



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