Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 100024
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
624 PM MDT Wed Aug 9 2017

.SHORT TERM...(Tonight through Thursday night)
Issued at 328 PM MDT Wed Aug 9 2017

Latest radar and GOES satellite this afternoon shows the influence from
an embedded shortwave trough that is currently progression across
the northern portion of our CWA. This wave, combined with
lingering moisture and the continued support of an upper level
jet, has made areas north of I-70 the focus for convection today.
The shortwave will trek through the area this evening with some
nocturnal showers persisting overnight before it exits to the
east. As for the rest of the CWA, shower and thunderstorm activity
has been representative of a typical summer day. That is,
scattered coverage with bouts of lightning and brief heavy rain.
Precipitable water (PWAT) on this morning`s sounding was down to
0.79 inches which is just 0.02 inches above the climatological
mean for this time of year.

This same moisture will once again be recycled on Thursday as the
overall synoptic pattern does not change. The 60-70kt jet will
remain parked aloft with the area of high pressure sitting south of
the Four Corners region. As a result, look for another day of
diurnal showers and thunderstorms with daytime highs right around or
slightly below normal.

.LONG TERM...(Friday through Wednesday)
Issued at 328 PM MDT Wed Aug 9 2017

The end of the work week will finally see a change in the synoptic
pattern as a broad upper level Pacific trough begins to elongate off
the coast of California. The intensification of this trough will
result in an increase in south-southwest flow over our area and
usher the area of high pressure further east. This shift will allow
for moisture to trickle in on the backside of the high and into our
southern zones with PWAT values increasing to over an inch for
Friday. Given the increase in moisture down south and the fact that
the upper level jet will remain overhead for both Friday and
Saturday, coverage and intensity of showers and thunderstorms could
be enhanced for both days, especially in the Four Corners area and
over the San Juan Mountains. As the previous forecaster
mentioned, coverage will not favor our northern areas as much
under a relatively drier airmass.

The aforementioned Pacific trough will gradually move inland late
Saturday and into Sunday and allow the high to migrate westward,
cutting off the moisture tap down south. PWATs will begin to
decrease as a result but moisture will continue to linger across the
region so we can still expect the typical orographic showers and
thunderstorms to fire off during the afternoon hours.

Extended models begin to diverge on potential solutions with the
state of the upper levels at the beginning of next week. The GFS
favors a split-flow and sends the parent closed low northeast into
Canada while a more shallow trough digs into the southwestern
CONUS. The Euro on the other hand elongates the trough and keeps
the closed low parked over the northwestern CONUS through midweek
before progressing northeast. This solution would allow for the
high pressure to elongate even further west into the Four Corners.
This actually pairs well with the latest 6 to 10 and 8 to 14 day
outlooks from the CPC, which highlight odds favoring below normal
precipitation for this region. Given the high model uncertainty
at this time, will continue to integrate the blended solution into
the extended grids.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 624 PM MDT Wed Aug 9 2017

Much less coverage of storms this evening with the highest
probability of impacts mainly along the I-70 corridor from Rifle
to Eagle. Gusty winds will be the main threat with these storms
throwing outflow boundaries. Otherwise VFR conditions should
dominate the forecast.

&&

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

$$

SHORT TERM...MMS
LONG TERM...MMS
AVIATION...TGJT



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