Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 171743

Area Forecast Discussion
National Weather Service GRAND JUNCTION CO
1143 AM MDT Mon Jul 17 2017

Updated aviation section

.SHORT TERM...(Today through Tuesday)
Issued at 410 AM MDT Mon Jul 17 2017

The upper ridge continues to be quashed by the stronger westerlies
intruding form the north...forced southward by strong troughing
across the high latitudes of NOAM. Heights are down from 24 hours
ago across the Intermountain West and as models suggested the
circulation is beginning to center over 4 Corners region. Plenty
of instability aloft which is keeping some showers going into the
early morning hours. Nothing very organized but radar imagery
shows a weak circulation dropping into the E.Tavaputs early this
morning. A more defined wave is upstream over SW.Utah which will
weaken as it plows into the ridge center over our CWA. However
suspect this feature will lead to a bit better coverage over the
northern half of the CWA than yesterday. Overall most areas will
have at least a small chance of seeing a passing storm today
though as in days past...the southern mountains will be favored
for the best coverage. Wind patterns show some weak difluence over
the the southern CWA this afternoon. This could trigger back-
building storms...and with moderate to heavy rainfall rates
possible...some runoff problems. Models suggest a temporary
downturn in PWAT across the north on Tuesday as drier sweeps in by
a dip in the westerlies. So do expect a slight downturn in
coverage over NE.Utah and NW.Colorado tomorrow afternoon with
storms will little chance to the south. Temperatures will continue
to run 5 to 10 degrees above normal.

.LONG TERM...(Tuesday night through Sunday)
Issued at 410 AM MDT Mon Jul 17 2017

PWAT will be shooting upward Tuesday night into Wednesday as the
ridge begins to reamplify across the West and the center of the
circulation shifts to the Plains. This places our CWA in a
favorable position to draw in a healthy batch of monsoonal
mositure with PWATs increasing to well above an inch by Wednesday
afternoon. This generally persists through the end of the week
with a daily threat of heavy runoff from storms. Temperatures for
the latter half of the week should be rolling back toward more
seasonable levels. It appears this strong plume of moisture will
be pushed eastward and suppressed to the south by the weekend as
energy dives out of the Canadian Prairies into the Great Lakes
with the ridge amplify back to our west.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1143 AM MDT Mon Jul 17 2017

Gusty outflow winds will be the greatest threat for aviation
travel today across eastern UT and western CO. A weak disturbance
passing across northern UT this morning is anticipated to move
across NE Utah and NW Colorado this afternoon.. and short term
forecast models picking up and uptick of showers and thunderstorms
across this area between 22z and 04z. Added tempos based on
highest likelihood of these tstorms for the 18z issuance of the
TAFs. A passing shower or tstorm could potentially impact airport
ops temporarily, however, feel that this likelihood continues to
be very small.




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