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Area forecast discussion 
National Weather Service Grand Junction Colorado
401 am MDT Wednesday Sep 17 2014

Short term...(today through thursday)
issued at 355 am MDT Wednesday Sep 17 2014

Middle and high level moisture continues to drift northward into the
forecast area this morning along the northern periphery of Odile
moisture as it lifts into Arizona. GOES sounder data indicating
precipitable water values near The Four Corners climbing above an
inch already and with northward drift of this moisture...should
see a few more storms fire across our southern mountains and
valleys. In addition...surface dew points climbing steadily into the
50s across southeast Utah this storms will have to
potential to generate locally heavy rain once they get rolling.
Have nudged probability of precipitation up a bit to cover this potential and may still be
on the low later shifts will need to monitor closely.
North of the San Juans...few more clouds expected today with
isolated storms...mainly over the higher terrain. Temperatures
will be a degree or two cooler in most areas...more in line with
the cooler mav guidance.

The remnants of Tropical Storm Odile will move into southern
Arizona tonight...then slowly move to the east-northeast through
the next 48 hours. Models still show some differences in the
track and speed...with the NAM the slowest and farthest north. By
late Thursday afternoon...the NAM shows the remnant circulation
center over east central Arizona...with the GFS placing it to the
southeast into New Mexico. North of the disturbance...high
pressure will dominate Utah/Colorado for a Rex pattern across the inter-
mountain region and Desert Southwest. The high pressure over our
forecast area will be fairly effective at blocking Odile's deeper
moisture...keeping the bulk of it to our south.

However expect that a few showers and thunderstorms will persist
this evening...and possibly increase for a time due to the
moisture that will have seeped northward across the southern
border. Then on Thursday...we should see an uptick in showers and
thunderstorms. But coverage will mostly be isolated in nature as
the better moisture still remains at Bay. The south will be

Long term...(thursday night through tuesday)
issued at 355 am MDT Wednesday Sep 17 2014

By Thursday night...the high over the central rockies will begin to shift
eastward as a Pacific shortwave moves towards the Great Basin. This
puts US under a southwest flow which may finally help carry some
of Odile's moisture into the forecast area. The western trough
will split...and cut off a low along the Southern California coast through
Friday. In the northern branch flow...a weak disturbance will brush
the northern portion of the County Warning Area...and possibly help push what is
left of Odile across northern New Mexico. Models continue to
underplay the moisture that will reach into our forecast area as
compared to earlier runs. But Friday should be our best day for
precipitation. The northern wave will provide a boost across the
northern portion of the area...with the south in proximity to the
remnants of Odile. The present forecast handles the situation well
with mostly chance probability of precipitation for the mountains...and slight chance in
the valleys. So will not make any big changes at this time.

Saturday will be a down day as subsident flow in wake of exiting
northern wave settles in. Have nudged temperatures up and lowered probability of precipitation on
Saturday as a result. Major changes appear to be in store late in
the weekend and through early next week and the deep closed
low off the California coast will lift east-northeast into the Great Basin.
This will draw up another surge of monsoonal moisture Sunday with
the low slowly working into the Great Basin on Monday. Deep
southerly difluent flow out ahead of the approaching low combined
with abundant moisture will set the stage for another significant
precipitation event. Confidence has been boosted a bit with some
model continuity developing with the European model (ecmwf) falling in line with
yesterdays GFS run. Will continue to ramp probability of precipitation up through the
later part of the extended while knocking temperatures back a bit...or
closer to seasonal norms. Plenty of time for refinement to the
forecast...but potential for widespread rain looks to be on the
rise as we roll into the new work week.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 355 am MDT Wednesday Sep 17 2014

Isolated to scattered showers and thunderstorms will develop after
18z today with locally heavy rain possible along and south of the
San Juan Mountains in southwest Colorado and south of Blanding
Utah in southeast Utah. Gusty winds to 40 miles per hour and small hail will
also be possible. Expect occasional mountain obscurations this
afternoon as thunderstorms develop. A few storms will drift into
the vicinity of ktex and kdro late this afternoon and into the
early evening hours. Otherwise...VFR conditions persist at
terminal sites through tonight.


Gjt watches/warnings/advisories...


Short term...jdc/eh

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