Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Grand Junction Colorado
352 am MDT Wednesday may 27 2015

Short term...(today through thursday)
issued at 352 am MDT Wednesday may 27 2015

The southern trough will work into Arizona today and while remaining
slightly will phase with the Idaho low for a broad trough
over the Great Basin. While it appears that moisture will decrease a
little...slightly lower precipitable water and dew points...we will
still see another round of afternoon convection. However coverage
will probably be a little less. Then the remnants of the southern the form of a weak shortwave ejecting from the base of the
trough...will pass over our forecast area late tonight. In addition
a weak cool front will work through the forecast area from the
northwest. This combination...along with a still moist air mass will
allow some showers and storms to persist beyond midnight.

The Great Basin trough...dominated by the northern branch low...will
approach on Thursday with the trough axis reaching our northwest corner
late Thursday afternoon/early evening. A weak-moderate upper level jet
core also approaches during the afternoon providing some support.
Moisture remains deep for late may...around 0.5 inch precipitable
water. Thursday afternoon will have slightly increased instability
with subtle cool advection aloft...especially north of I-70.
Therefore look for continued showers and thunderstorms...
increasing and strengthening in the afternoon.

Long term...(thursday night through tuesday)
issued at 352 am MDT Wednesday may 27 2015

The trough over the Great Basin and northern rockies will move
through the forecast area Thursday night through Friday. Dynamic support for
deep convection will slide east of the area early Thursday evening...
then drier air will begin building into the area from the SW.
Believe clouds and showers will remain over the northern Colorado mts
through the night and throughout Friday as another secondary
shortwave slips in behind the main trough. The surface cold front
should back up along the Front Range and push a little west such
that showers will remain possible along the Continental Divide
through Friday night. Some return flow from the southeast may keep clouds and
precipitation over the eastern portions of the San Juans and the lower
elevations over Archuleta County Sat and Sat night. Monday and
Tuesday both look dry and warmer with the exception of a chance of
afternoon and evening showers/thunderstorms in the residual moisture along
the Continental Divide.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 352 am MDT Wednesday may 27 2015

Isolated to scattered showers persisted overnight...but as drier
air moves in from the west...precipitation should be limited to the
higher mountains through 18z today. This afternoon...scattered to
numerous showers and thunderstorms will redevelop and continue
through the night as the main trough approaches from the
northwest. Expect vcsh and thunderstorms in the vicinity for some taf sites this afternoon
and tonight. The main concerns will be heavy rain dropping
cig/vis...small hail and some gusty winds up to 40 miles per hour or so.


Gjt watches/warnings/advisories...


long term...cirrocumulus

National Weather Service Glossary of Abbreviations