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Area forecast discussion 
National Weather Service Grand Junction Colorado
338 am MDT Monday Jul 6 2015

Short term...(today through tuesday)
issued at 337 am MDT Monday Jul 6 2015

After the disturbance passed Sunday evening the ridge is
flattened into the desert SW today. A closed low off the
California coast pushes onshore by Tuesday. This pattern will
bring a downturn in showers today but another surge on Tuesday.

Today...W-NW flow aloft has brought in slightly drier air with
precipitation water values between 0.75 and 1.0 inch. This is only dry in
relation to the near record moisture amounts we had over the
weekend. Isolated morning showers and storms will become scattered
this afternoon favoring the mountains and southern valleys where
moisture is deepest. Temperatures will recover closer to normal
this afternoon...still nicely cooler than the hot conditions of
last week.

Tonight...weak disturbances are resolved differently in the models
but hint at weak forcing that may keep a few storms going through
the night. No portion of the forecast area looks favored for
showers. the low pushes towards the California coast the SW
ridge weakens. Flow turns to west-southwest and allows deeper moisture to
begin to return. A more organized disturbance lifts into southeast Utah
through the afternoon. Storm coverage will increase from SW to NE
through the day. Daytime temperatures take another dip under
clouds and showers.

Long term...(tuesday night through sunday)
issued at 337 am MDT Monday Jul 6 2015

Monsoonal flow really kicks in Tuesday evening as cyclonic flow
from the closed low off the California coast and anti-cyclonic
flow from the high pressure over the Gulf Coast meet over Mexico
and keep moisture streaming into the area. Granted...precipitable waters are a
bit lower than seen in recent days but values around 1 inch still
merit attention. Models agree that the convection that fired
earlier Tuesday will continue through the evening and possibly
past midnight as a shortwave moves overhead. Obviously...chances
for heavy rain continue as well.

Convection continues Wednesday but as the low approaches...a
deformation zone sets up over the northern half of the area which will
be the focus for precipitation through Thursday evening. By this
time...nam12 lowers precipitable waters as stream of moisture slowly shuts off
while GFS keeps the plume in full force. Leaning towards nam12 as
forecast precipitable waters from both models do decrease Thursday and height
rises indicate high pressure building in from the southeast...also
another reason that moisture slowly shuts off.

By Friday...the closed low rapidly opens up and weakens as it
becomes an open wave. The high to the southeast also continues to
build in to the area so we can expect convection favoring higher
terrain though coverage should be less than seen over the last few
days. Saturday and Sunday...the center of high pressure will have
retrograded and set up over New Mexico. This location will effectively
cut off the moisture from the south. A few isolated showers
possible but nothing of great import.

Clouds and precipitation will continue to keep temperatures below climatology though a
return to more normal values expected Saturday and beyond.


Aviation...(for the 12z tafs through 12z Tuesday morning)
issued at 337 am MDT Monday Jul 6 2015

Some morning fog/low clouds showing up near the Steamboat and
Craig area this morning but they should quickly dissipate after
sunrise. More convection develops after 18z today with some heavy
rain and occnl gusty winds affecting kdro...and ktex and to a
lesser extent kase...kege...and kril. Convection will die down
after 03z though some isolated showers/storms will continue
through 09z. Even with this inclement weather...taf sites will
remain VFR/above ils breakpoints for the majority of the day.


Gjt watches/warnings/advisories...


Short term...Joe
long term...tgr

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