Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 121631
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
931 AM MST Mon Feb 12 2018

.UPDATE...
Issued at 931 AM MST Mon Feb 12 2018

Added zone 3 - Roan and Tavaputs Plateau - to a winter weather
advisory through Tuesday morning. Conditions are beginning to
deteriorate over Douglas Pass due to a band of snow pushing
northward this morning. This trend will continue throughout the
day as these convective bands set up and gradually move
northeastward.

UPDATE Issued at 742 AM MST Mon Feb 12 2018

First of many updates expected with this dynamic system. Snow has
been falling steadily along the Highway 160 corridor from Pagosa
to Durango as temperatures cooler than anticipated there. Another
band of heavier precipitation has set up along the DeBeque to Silt
Corridor with roadways becoming covered already. The big question
now is when and especially if this precipitation will be able to
change phase with good lift through the day. Have added advisories
here until early afternoon and will be re-evaluating latest
satellite...radar and ground truth data. Models still dialing in
on a defined band of heavier precipitation oriented SW to NW
in the vicinity of EC Utah to NW Colorado. This band could produce
a prolific area of precipitation including a band of impressive
snow totals. Stay tuned.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 341 AM MST Mon Feb 12 2018

As we approached sunrise this morning clouds were thickening and
lowering across the area, especially over SW CO, as the next
winter storm approaches. A closed low will form over the western
Great Basin today and tonight, which will continue to draw
moisture into the area from the south. A strong jet will be over
the area as well adding to the broad uplift that will remain over
the forecast area today and tonight and gradually slide north and
west Tuesday. Have continued the winter weather products in effect
and expect widespread precipitation, especially mountain snow,
for the next 24 hours.

LONG TERM...(Tuesday night through Sunday)
Issued at 341 AM MST Mon Feb 12 2018

The closed low off of the California coast on Tuesday night will
slowly move east and link up with a trough dropping south over the
Great Basin on Wednesday into Thursday. Forecast models are
advertising another round of precipitation as this warm, moist
airmass interacts with a much colder airmass dropping down from the
north. 700 mb temperatures are forecasted to drop from -2C on
Wednesday morning to -8C across the south by Thursday morning with
snow levels dropping to valley locations. The best focus for the
precipitation will be Wednesday night into Thursday. Drier,
northwest flow will develop on Friday and Saturday before another
trough drops into the Great Basin by late Sunday and is expected to
impact our forecast area early next week.

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 341 AM MST Mon Feb 12 2018

VFR conditions will last at most TAF sites for a short time today.
At 3 AM MST CIGS were lowering over SW CO and SE UT as the next
winter storm approaches from the west. CIGS below ILS breakpoints
should reach KDRO by about 15Z and spread north and east
throughout the day, reaching KGUC and KGJT by 19Z. ILS CIGS should
develop over KRIL, KEGE, KASE and KHDN by 22Z. Periods of MVFR
and IFR CIGS and vsbys are possible at all TAF sites through 12Z
Tue and this storm moves through. Mountains will be obscured as
well.

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 6 AM MST Tuesday for COZ018-019.

     Winter Storm Warning until 6 AM MST Tuesday for COZ019.

     Winter Weather Advisory until 6 AM MST Tuesday for COZ009-012-
     013.

UT...None.

$$

SHORT TERM...CJC
LONG TERM...MPM

.LONG TERM...(Wednesday through Monday)
Issued at 742 AM MST Mon Feb 12 2018

The closed low off of the California coast on Tuesday night will
slowly move east and link up with a trough dropping south over the
Great Basin on Wednesday into Thursday. Forecast models are
advertising another round of precipitation as this warm, moist
airmass interacts with a much colder airmass dropping down from the
north. 700 mb temperatures are forecasted to drop from -2C on
Wednesday morning to -8C across the south by Thursday morning with
snow levels dropping to valley locations. The best focus for the
precipitation will be Wednesday night into Thursday. Drier,
northwest flow will develop on Friday and Saturday before another
trough drops into the Great Basin by late Sunday and is expected to
impact our forecast area early next week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 341 AM MST Mon Feb 12 2018

VFR conditions will last at most TAF sites for a short time today.
At 3 AM MST CIGS were lowering over SW CO and SE UT as the next
winter storm approaches from the west. CIGS below ILS breakpoints
should reach KDRO by about 15Z and spread north and east
throughout the day, reaching KGUC and KGJT by 19Z. ILS CIGS should
develop over KRIL, KEGE, KASE and KHDN by 22Z. Periods of MVFR
and IFR CIGS and vsbys are possible at all TAF sites through 12Z
Tue and this storm moves through. Mountains will be obscured as
well.

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 6 AM MST Tuesday for COZ018-019.

     Winter Storm Warning until 6 AM MST Tuesday for COZ019.

     Winter Weather Advisory until 6 AM MST Tuesday for COZ009-012-
     013.

UT...None.

$$

SHORT TERM...CJC
LONG TERM...MPM

.LONG TERM...(Wednesday through Monday)
Issued at 742 AM MST Mon Feb 12 2018

The closed low off of the California coast on Tuesday night will
slowly move east and link up with a trough dropping south over the
Great Basin on Wednesday into Thursday. Forecast models are
advertising another round of precipitation as this warm, moist
airmass interacts with a much colder airmass dropping down from the
north. 700 mb temperatures are forecasted to drop from -2C on
Wednesday morning to -8C across the south by Thursday morning with
snow levels dropping to valley locations. The best focus for the
precipitation will be Wednesday night into Thursday. Drier,
northwest flow will develop on Friday and Saturday before another
trough drops into the Great Basin by late Sunday and is expected to
impact our forecast area early next week.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory until 6 AM MST Tuesday for COZ003-009-
     012-013-018-019.

     Winter Storm Warning until 6 AM MST Tuesday for COZ019.

     Winter Weather Advisory until 3 PM MST this afternoon for COZ007.

     Winter Weather Advisory until 1 PM MST this afternoon for COZ022-
     023.

UT...None.
&&

$$

UPDATE...TGJT
SHORT TERM...CJC
LONG TERM...MPM
AVIATION...CJC



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