Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 140956
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
356 AM MDT Mon Aug 14 2017

.SHORT TERM...(Today through Tuesday)
Issued at 339 AM MDT Mon Aug 14 2017

A weak vort max is moving across central portions of Colorado at
this hour and is causing a few lightning strikes over the Grand
Mesa down into Paonia. Radar returns are incredibly small so maybe
a few drops of rain will accompany the rumbles as the storms roll
through. By daybreak, this line should be just about out of the
CWA.

Today will be the last day of PWATs in the .75 to .80 inch range
as a large swath of drier air is poised to move into the area
later tonight. Until then, another round of convection is expected
with coverage looking best for the northern half of Utah and
Colorado thanks to an approaching cold front. Would not be
surprised to see a few pop-ups over the San Juans, however.
Convection should fire around noon and continue through the
evening hours. As usual, dangerous lightning, small hail, gusty
winds, and some heavy rain are always possible near and under the
strongest storms. The highest terrain will see convection first
with a few drifting into adjacent valleys. If models are to be
believed, the front will cause showers to continue over the
northern valleys through Tuesday morning. PoPs follow suit with
this thinking.

The front will be very slow to move on Tuesday and it looks as
though best forcing will remain to our north keeping most
precipitation in Wyoming. Upper levels do show the front moving
through but as it moves down the front range, that`s when
precipitation really picks up...but for that area. So this front
looks to be mainly dry for us though an odd shower or storm can`t
be ruled out in the afternoon, again generally north.

Temperatures will drop about 3 to 5 degrees below normal once the
front moves through.

.LONG TERM...(Tuesday night through Sunday night)
Issued at 317 PM MDT Sun Aug 13 2017

An embedded shortwave trough in the northwesterly flow aloft will
move through the region both Wednesday and Thursday, kicking off
another round of at least isolated to scattered showers and
thunderstorms each afternoon. Northwesterly flow will remain
overhead through the end of work week so not much change in the
overall weather pattern for our region except for temperatures
rising back to normal for Friday and Saturday.

Going further into the extended period, models begin to diverge on
potential synoptic solutions by the weekend. The GFS introduces a
broad upper level Pacific trough by Saturday and has it gradually
progressing inland through early next week, increasing southwesterly
flow over our forecast area. The Euro on the other hand takes the
area of high pressure centered over the southeastern CONUS and
tracks it westward into our region, potentially bringing an increase
in moisture from down south. Given model uncertainty, PoPs in the
extended grids remain on the conservative side for now, representing
typical summertime convection.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 339 AM MDT Mon Aug 14 2017

Yet another day of convection in store with areas north now being
favored though a few popups not out of question for southern
areas. Any cells that move over TAF sites will bring some gusty
winds and heavier rain. A quick drop to MVFR conditions is
possible if/when storms move over TAF sites. ILS breakpoints may
also be met from time to time but should not stay down for too
long.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

SHORT TERM...TGR
LONG TERM...MMS
AVIATION...TGR



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