Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 220208
AFDGJT

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
808 PM MDT Wed Jun 21 2017

.SHORT TERM...(Tonight through Thursday night)
Issued at 305 PM MDT Wed Jun 21 2017

A 596 DM ridge of high pressure remains centered over the
southwestern CONUS this Wednesday afternoon. Diurnally driven
afternoon convection has once again developed over the higher
terrain, aided by marginal mid-level moisture still lingering on
the northern fringes of the ridge of high pressure. Some lightning
has been noted throughout the day with this convection, as well
as briefly gusty winds. DCAPE values sit in the 1000-2000 range
per model sounding analysis, with the KGJT morning sounding
indicating around 1570J/kg. Temperatures remain on track this
afternoon, and convection should diminish after sunset this
evening.

One more day of near record warmth is expected on Thursday before
temps cool down a bit this weekend. A weak 300mb speed maximum
will pass north of the Four Corners on Thursday morning. This
increase in winds aloft will tend to aid/organize any
thunderstorms that do form during the afternoon hours, and some
dry lightning is again expected area-wide in the higher terrain.
There will be an uptick in afternoon winds and wind gusts as well,
however guidance is in fairly good agreement keeping values below
Red Flag Warning thresholds. Will continue to hold off on any
headlines in this forecast package. Once again with the loss of
daytime heating, any lingering convection will diminish
overnight.

.LONG TERM...(Friday through Wednesday)
Issued at 305 PM MDT Wed Jun 21 2017

A diffuse frontal boundary will drift south and east through
eastern Utah and western Colorado on Friday morning as a larger
upper-level trough moves east through the high plains. This front
will act to take the edge off the extreme heat over the western
slope on Friday and through the weekend. Temperatures are still
expected to be around 5 degrees above average each day, however
record heat will no longer be in the forecast. As the front passes
Friday, some mid-level cloud cover will pass through. Mostly
clear skies will return on Saturday and Sunday as the southwestern
ridge of high pressure reloads for early next week.

The next peak in afternoon high temperatures will come early next
week as the renewed ridge of high pressure in the southwest builds
eastward. The hottest day during this time period will likely come
on Tuesday as the ridge axis passes just east of the Four Corners
and southwesterly warm air advection inches mid-level temperatures
up slightly. Beyond Tuesday, models begin to diverge with the
evolution of a weak trough moving in along the Pacific coast. The
GFS shows a deeper system that brings a strong gradient and a
windy day on Wednesday, before a frontal passage and possible
thunderstorm activity next Thursday. The ECMWF keeps this trough
weaker and much farther north, with dry weather and mostly zonal
flow through the period. This forecast package reflects the drier
solution, in line with the operational ECMWF as well as EPS
ensemble guidance.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 808 PM MDT Wed Jun 21 2017

A few showers will linger this evening bringing a slight chance
for rain to KMTJ and KTEX through 04Z. This activity may generate
strong outflow winds at these sites and KEGE before midnight.
Otherwise, VFR conditions and CIGS above 18,000 feet MSL will
continue through the night and through midday Thursday. Showers
and thunderstorms are expected over the mountains Thursday
afternoon resulting in conditions similar to today`s.

&&

.FIRE WEATHER...
Issued at 305 PM MDT Wed Jun 21 2017

Fire Weather conditions will be near but just below critical
levels on Thursday. Some stronger winds aloft will move over the
region Wednesday evening and Thursday morning and as mixing
commences during the afternoon hours, a few gusts upward of 20 mph
can be expected. Regarding convection, isolated afternoon
thunderstorms will diminish overnight. Dry lightning is a
possibility, however most of the convection will remain weak and
likely not produce any strikes. Dry lightning is again possible on
Thursday however chances are lower. The best opportunity will be
in the higher mountains along the Continental Divide.
Precipitation chances will drop to near 0 through the weekend.

&&

.HYDROLOGY...
Issued at 305 PM MDT Wed Jun 21 2017

A flood advisory has been issued for the Roaring Fork River in
Aspen as snowmelt and tunnel closures upstream have caused the
river to reach bankfull. This advisory will run through Friday
evening.

A number of streams and creeks also continue to run strong, cold,
and high and will continue to do so through the week. Where water
is running high, river banks may become saturated and unstable.
Lowlands along the rivers may also become inundated with water.
Remember if you are going to raft, kayak or tube on the rivers be
sure to always wear a life jacket.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Heat Advisory until 10 PM MDT Thursday for COZ006.

UT...Heat Advisory until 10 PM MDT Thursday for UTZ022-027-029.

&&

$$

SHORT TERM...MAC
LONG TERM...MAC
AVIATION...NL
FIRE WEATHER...TGJT
HYDROLOGY...TGJT



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