Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 260058

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
658 PM MDT Tue Jul 25 2017

Issued at 638 PM MDT Tue Jul 25 2017

Increased PoPs and expanded coverage for higher PoPs down into
southeast Utah, as storms are developing most intensely in
southeast Utah into southwest Colorado on the axis of deepest
moisture. Threat for heavy rain is high with these storms and
should continue well into the evening hours as this area
propogates to the northeast. SPC mesoanalysis indicates 1.5 inch
precipitable water in this region as well as CAPE values up to
3000 J/kg which is quite impressive and being realized as
preliminary and non-operational GOES-16 IR showing cloud tops as
low as -75 degrees C in the strongest overshooting tops indicating
persistent strong updrafts.


.SHORT TERM...(Tonight through Wednesday night)
Issued at 302 PM MDT Tue Jul 25 2017

PWAT is climatologically maxed out this afternoon across the
Utah/Colorado border. We had one batch of rain move north out of
the cwa by noon with some clearing across the SW in the wake of
this rainfall. This heating...and stronger winds aloft associated
with an organized wave moving northward across Central Utah is
creating conditions favorable for stronger storms. Small
hail...heavy rainfall and possibly some gusty winds will be
possible with these storms as they move northward out of Southeast
Utah into West Central and NW Colorado through the evening.
Widespread showers and storms will also continue over the
remainder of the region through the early morning hours this wave
moves through and forces the main moisture plume eastward. Do
expect a decent downturn in the precipitation by sunrise as
subsidence behind this wave kick. Some drier air will be advecting
in from the west on Wednesday but deeper moisture remains over
our southern mountains and when combined with a bit more
sunshine...showers and storms should become likely over the hills
by early afternoon. The eastern valleys should see some storms
drift in through the late afternoon...with drier air and less
focus limiting the storms in the western valleys. Temperatures
will bump up a bit on Wednesday with less cloud cover but still
remain slightly below normal.

.LONG TERM...(Thursday through Tuesday)
Issued at 302 PM MDT Tue Jul 25 2017

By Thursday the upper high will begin to migrate back to the West
as energy digs across eastern CONUS. This will reduce the
northward extent of the monsoonal plume but keep it located to the
south of our border.  We will keep afternoon storms in the
forecast but with a gradual downturn Thursday into Friday. The
models have changed due to a stronger trough located over the Left
Coast going into this late week period. Earlier trends had the
high reforming back over the Great Basin. However now this high
is centered back over our CWA by Saturday and suppressed a bit to
the south due to stronger westerly flow across the US/Canada
border. This seems to allow a bit more monsoonal moisture to seep
under the ridge and begin and upward trend to storms going into
the weekend and early next week. Expect seasonal temperatures
through the long term period.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 638 PM MDT Tue Jul 25 2017

Widespread to numerous showers and thunderstorms will continue to
develop across much of the area, particularly focused on southeast
Utah and southwest Colorado with this area moving northeast
towards west-central Colorado and the north late this evening.
Most if not all TAF sites will see VCTS with potential for
stronger storms to track over these areas, producing heavy rain,
frequent lightning, small hail and gusty outflow winds. CIGS and
VSBY will be reduced below ILS breakpoints at times through 06Z
this evening before activity lessens overnight. Storms look to
redevelop over the higher terrain after 18Z Wednesday with some
adjacent valleys being impacted late Wednesday afternoon into the


CO...Flash Flood Watch until midnight MDT tonight for COZ001>014-

UT...Flash Flood Watch until midnight MDT tonight for UTZ022>025-



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