Area Forecast Discussion
Issued by NWS Grand Junction, CO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS65 KGJT 292139

Area Forecast Discussion
National Weather Service Grand Junction CO
339 PM MDT THU SEP 29 2016

.SHORT TERM...(Tonight through Friday night)
Issued at 330 PM MDT Thu Sep 29 2016

Deep tropical moisture is in place over the forecast area, deepest
south. The atmosphere is warm with weak instability at best, so
warm rain processes dominate. The dynamical remnants of former
T.S. Rosyln was over the Mogollon Rim in eastern AZ this afternoon
and will push across the region tonight. Associated heavy showers
this evening in the Four Corners holds some potential for flash
flooding in the canyon country of SE Utah. Fog could be a problem
tonight into Friday morning in areas that received significant
rain today and along south-facing slopes.

Friday, better moisture remains across the south with some
sheared energy working east across SW and west-central Colorado
through the day. With warm temperatures aloft, instability will
remain limited so showers will favor the Colorado mountains from
the Roan- Tavaputs- Flattops southward. Only isolated showers are
expected Friday night.

.LONG TERM...(Saturday through Thursday)
Issued at 330 PM MDT Thu Sep 29 2016

Over the weekend the upper flow turns to a drier SW. Temperatures
recover to near normal and mainly diurnal showers and
thunderstorms will favor the mountains. A colder and stronger
West Coast low develops along the OR-CA coast. Sunday, a strong
vort max digs down the west side of the trough progressing it into
the Great Basin on Monday. Models have good timing agreement but
differ with the strength and position of the passing low. The GFS
has all the energy tightly closed and passing through the southern
half of the forecast area. The EC is more elongated with much of
its energy stretched northward through Wyoming. Both solutions
have strong SW winds developing early Monday as the cold front
passes in the afternoon. These storms may be strong with
increasing instability and a veering and speed shear environment.

Monday night-Tuesday night, the upper flow veers to NW in strong
cold advection. The GFS has a -24 cold core grazing the north
Monday night then after a bit of a lull on Tuesday a second wrap-
around cold core passes Tuesday night. This could bring
significant snowfall to the mountains along the Continental Divide
as far south as the NW San Juans. The EC solution would limit snow
accumulations to NW Colorado. Elsewhere expect below normal
temperatures and freezing Tuesday night temperatures are possible
in the higher valleys. Wednesday, a drying and warming trend


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 330 PM MDT Thu Sep 29 2016

VFR with intermittent MVFR conditions in showers/cigs will remain
possible through 03z this evening. Instability and therefore
thunderstorm chances are low. Ceilings may drop below ILS
breakpoints at times overnight and patchy slope fog will obscure
higher terrain along and south of I-70. KTEX DRO KCNY terminals
have the highest chance of ceiling or visibility impacts. Any fog
will dissipate by 14z Friday. There is a chance of showers and
thunderstorms through Friday afternoon.



AVIATION...JOE is the U.S. government's official web portal to all federal, state and local government web resources and services.