Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 211749

Area Forecast Discussion
National Weather Service Grand Junction CO
1149 AM MDT THU JUL 21 2016

Issued at 1149 AM MDT Thu Jul 21 2016

An embedded disturbance shifting slowly northwestward will help
focus deep monsoon moisture over portions of west-central and
northwest Colorado this afternoon and evening. Slow moving
thunderstorms have the potential to produce excessive rainfall
possibly leading to flash flooding. Therefore, a Flash Flood Watch
has been issued for portions of the I-70 corridor north of the
Colorado River, the Roan and Tavaputs Plateaus and the Flat Tops.
Also included are drainages in northwest Colorado adjacent to the
higher terrain previously mentioned.


.SHORT TERM...(Today through Friday)
Issued at 338 AM MDT Thu Jul 21 2016

Little change in the upper pattern was noted on the 00z h5 hand
Analysis chart across the lower 48. High pressure over the
Southern plains continues to help draw monsoon moisture northward
Across the 4 corners region. Pwat remains near and inch and has
Allowed some isolated storms to produce localized heavy rainfall
And flooding issues. Today will be now different with convection
Again flaring up in the afternoon aided by strong heating. There
Has been some storms surviving past midnight associated with a
wave Near the 4 corners we have been able to track the past few
days. Northeast utah is also in the entrance region of a jet aloft
which Has kept isolated storms firing form the tavaputs to the
uintas. Would suspect both features will come into play later
today with The better focus associated with the wave in southeast
utah. There Was also a decent outflow boundary pushed toward the
tavaputs last Evening that could be a focus later today. Would
like to see a More organized wave moving through to focus the
convection. Expect Localized flooding and debris flows are
possible again today but Confidence on widespread flooding issues
not high enough to issue A watch...but it was considered. Isolated
storms or a complex is Likely to survive again into the night but
again confidence low. A Northern stream wave moving across the
northwest border will begin To push the southern plains high
center westward...disrupting the Efficient tap of moisture. The
westerlies will become more Dominant late tomorrow and bring a
different regime into the Region. However do expect another
productive round of storms on Friday with heavy rainfall and maybe
some more organized storms in Our northeast zones as stronger
winds move in aloft. Temperatures Remain steady state today with a
slight warmup tomorrow...all near Normal for this time of year.

.LONG TERM...(Friday night through Wednesday)
Issued at 338 AM MDT Thu Jul 21 2016

By Saturday, the large scale pattern change begins. The Pacific
NW upper Low ejects through the northern Rockies. This turns the
upper flow from SW to a drier west. The subtropical High also
expands across the southern tier of states into the SE Pacific.
All of this brings a drying and warming trend to the forecast area
that continues into at least next Wednesday. The latest trend is
for marginal moisture to linger over the southern and central
zones for some late-day, mainly-mountain storms. The northern
zones see a return to dry and breezy conditions that may raise
fire weather concerns.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1149 AM MDT Thu Jul 21 2016

Thunderstorm activity has already begun increasing with many
flight terminals under the threat of passing thunderstorms.
Highest confidence in the mountain forecast terminals experiencing
lower flight criteria from heavy rain temporarily reducing vsby.
Stronger outflow winds are not favored in this moist atmosphere
however can not be ruled out if a storm quickly collapses in which
gusts near 45 will be possible. 21/20Z-22/03Z will be the period
of greatest storm coverage with a decrease through the early
morning hours anticipated.


.GJT Watches/Warnings/Advisories...

CO...Flash Flood Watch until 9 PM MDT this evening for COZ002-003-005-




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