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Area forecast discussion 
National Weather Service Grand Junction Colorado
1030 PM MDT Wednesday Jul 23 2014

Short term...(tonight through Thursday night)
issued at 335 PM MDT Wednesday Jul 23 2014

Shortwave rotating through the base of a deep trough over the
Pacific northwest has caused the high pressure center to shift
eastward to central Colorado this afternoon. This has opened the
monsoonal moisture tap as evidenced by increased precipitable water in area
soundings and increased dewpoint values...especially across
eastern Utah. In turn...this has led to increased shower and
thunderstorm activity this afternoon.

Models indicated that deep moisture will continue to increase
overnight with precipitable water values reaching 0.9 inches in northwest Colorado by
sunrise Thursday. A weak shortwave combined with divergence aloft
should sustain nocturnal showers and embedded thunderstorms
overnight.

Moisture depth increases further Thursday with precipitable water values near 1.2
inches over southeast Utah during the afternoon. Flow will shift
to a more westerly fetch which will help deepen moisture over the
Colorado mountains as well. Gave some thought to a Flash Flood
Watch over portions of The Four Corners where moisture deepest and
storms will be slow moving. However...training storms not likely
and coverage of storms on the low side so will hold off.
Meanwhile...favorable westerly flow and divergence aloft over the
Colorado mountains should yield increased storm coverage. Expect
storms will become more efficient rain producers as the day
progresses in response to rising sub-cloud layer moisture.

Expect normal downturn in moist convective activity late Thursday
evening with some nocturnal showers lingering overnight.

Guidance mixed on high forecast for Thursday. Mav guidance
appeared much too warm given increased moisture which will
naturally lead to more clouds and showers. Meanwhile...felt met
too aggressive with the cooling. Consequently...went with values
between the two...but tilted toward the cooler met.

Long term...(friday through wednesday)
issued at 335 PM MDT Wednesday Jul 23 2014

On Friday subtropical moisture continues to flow up into our County Warning Area
as upper high center remains in the NE nm/Texas Panhandle area. Then
drier air expected for our area Saturday and Sunday as the upper
high shifts closer to The Four Corners area in response to the
east-southeastward moving upper low in Canada dropping into
the Great Lakes area.

Then upper ridge expected to rebuild over the western states and
up into western Canada beginning Monday...allowing subtropical
moisture to spread northward again to the west of our area and
also eventually into our area. GFS and ec models in general
agreement for our area during this period... and both indicate
the remnants of an easterly wave traveling around the upper high
and into our County Warning Area from the northwest during the Monday night-Tuesday time
frame. If this pans out...we could be looking at a rather active
period for convection with this feature. Then would expect a
downturn in convective activity on Wednesday in the wake of this
feature under a northwest flow aloft.

Temperatures in the lower levels of the atmosphere not expected
to change much through the next 7 days...as high pressure aloft
continues over the area. Maximum and min temperature variations
from day to day through the period will generally be dependent
on proximity and extensiveness of cloud cover and
showers/thunderstorms.

&&

Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1030 PM MDT Wednesday Jul 23 2014

Areas of showers and thunderstorms will continue to affect parts
of eastern Utah and western Colorado late tonight...eventually
diminishing towards morning. These storms may result in
local mountain obscurations and may pass over taf sites through
around 09z. Some storms will generate strong outflow winds to 35
miles per hour with isolated stronger gusts possible. Localized moderate to
heavy rain is possible...though taf sites are unlikely to see a
degradation of flight category below VFR. Showers and embedded
thunderstorms will again increase by midday Thursday.

&&

Fire weather...
issued at 335 PM MDT Wednesday Jul 23 2014

Moisture will continue to spread northward across the area
through Friday with an uptick in late day thunderstorms...
though relative humidity values are expected to remain rather
low...as the bulk of moisture will be in the middle levels. On
Friday afternoon...some areas of the Uintah basin and the
northwest corner of Colorado may approach borderline critical fire
weather conditions based on winds and relative humidity...as dry air persists
and pressure gradient tightens a little. Later shifts will need
to take a closer look at the situation for possible Fire Weather
Watch.

Then some drying is expected for the weekend...followed again by
an increase of moisture next week beginning on Monday. Maximum
temperatures will remain at or above normal.

&&

Gjt watches/warnings/advisories...
Colorado...none.
Utah...none.
&&

$$

Short term...no layers
long term...jrp
aviation...eh
fire weather...jrp

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