Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 192327

Area Forecast Discussion
National Weather Service Grand Junction CO
527 PM MDT Tue Mar 19 2019

.SHORT TERM...(Tonight through Wednesday night)
Issued at 355 PM MDT Tue Mar 19 2019

As the low pressure system over the central Plains slides farther
east this evening the forecast area will fall under the col
between this system and a deep low off the West Coast. A few
convective showers associated with instability and a weak wave
brushing the southern Divide trailing the Plains system may bring
a few additional showers over higher terrain early this evening.
During the remainder of the night, skies will clear as dry air
filters into the region from the north.

Skies will remain mostly clear Wednesday morning though clouds
will begin building across southeast Utah later in the day as a
vort lobe rotating through the base of the closed low pressure
system moving onto the West coast approaches. Difluent mid-level
flow combined with jet level divergence are expected to provide
enough lift to generate isolated to scattered light showers over
southeast Utah where modest mid-level moisture will advect

Showers become likely over southeast Utah Wednesday night with
scattered showers developing over southwest Colorado as the West
Coast low center moves from the eastern Pacific over southern
California. Snow levels will be near 8500 feet so lower
elevations will see rain as this system comes in with accumulating
snow expected across areas above that elevation.

Overnight lows will be a bit below normal tonight due to clear
skies and light winds. Tomorrow`s highs will climb to near normal
levels with increased clouds limiting maximums during the
afternoon. However, those clouds will moderate temperatures on
Wednesday night and as a result, lows Thursday morning will be at
or above normal for most locations.

.LONG TERM...(Thursday through Tuesday)
Issued at 355 PM MDT Tue Mar 19 2019

The most active portion of the Pacific storm mentioned in the
short term discussion arrives Thursday as a lobe of vorticity
rotating out ahead of the low center pushes up across the Four
Corners region. Mid-level lift will combine with jet divergence
aloft, orographics provided by stiff southerly winds, and
deepening moisture to bring a period of heavy snow over the La
Sal, Abajo and San Juan Mountains which appears will linger into
the evening. Due to mild 7h temperatures associated with this
system, the lower elevations can expect rain, and the heavier
snow during this event should occur above the 8500 foot level.
Snow is expected to continue over the La Sal, Abajo and San Juan
Mountains Thursday night as the storm center moves northward over
east-central Utah, but accumulations will come at a more moderate
rate. Concurrently, as the system moves north snow and rain will
spread into the central and northern mountains of the forecast
area. Rain will shift to snow in the higher central and the
northern valleys during the night, but will switch back to rain
during the day on Friday. The storm center continues north-
northeastward to central Wyoming then the northern high plains
Friday into Friday night. As the storm shifts showers will become
scattered across the south while remaining likely across the
northern and central mountains.

Potential snowfall amounts could reach warning criteria for the
La Sal, Abajo and San Juan Mountains from Thursday through Friday
morning, so have gone ahead with a Winter Storm Watch for those
areas. The remaining mountains appear to be headed toward
advisory amounts, but since snow begins in the fourth period for
those higher terrain in the central and northern portion of the
forecast area, will wait until confidence in timing and amounts
improves before adding additional winter weather highlights.

A broad shallow trough will be over the region through the weekend
and into Monday which will allow scattered showers to continue.
Finally, on Tuesday a building ridge over the Rockies brings
drying to the area resulting in dry weather over the region.

Temperatures will be cooler than normal during the end of the week
as the storm discussed previously moves through the area. Though
showery conditions will persist during the weekend, temperatures
will close in on normal, rising to above normal levels Tuesday
beneath the high pressure ridge.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 527 PM MDT Tue Mar 19 2019

Widespread VFR conditions are expected across eastern Utah and
western Colorado through 00Z Wednesday evening. Locally breezy
winds will be possible through 03Z this evening before winds
become more terrain-driven. Mostly clear skies will prevail with
just some passing high clouds. After 18Z Wednesday afternoon mid
and high level clouds will increase across the south as the next
disturbance begins to impact the region.


CO...Winter Storm Watch from Thursday morning through late Thursday
     night for COZ018-019.

UT...Winter Storm Watch from Wednesday evening through late Thursday
     night for UTZ028.



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