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Area forecast discussion 
National Weather Service Cheyenne Wyoming
1215 PM MDT Tuesday Jul 22 2014

issued at 1209 PM MDT Tuesday Jul 22 2014

No major adjustments to the forecast necessary for this mornings
update. Warmer middle-level temperatures can be noted comparing the
visible satellite imagery to this time yesterday. A few shallow cumulus
just now starting to developing north of the Ferris/Seminoe
Mountains as well as the northern end of the Laramie range. Latest high
resolution model output target two areas for convective activity
as the cap breaks later this afternoon. The first convective
complex will develop across northeast Wyoming by around middle-
afternoon...moving east and then southeast affecting far east
central Wyoming and the northern Nebraska Panhandle. The second
area is across southern Platte/Goshen counties as well as Laramie
County between 4-7p. Undoubtedly the cap will hold strong through
that time...but once it breaks...sbcapes of around 2000 j/kg will
be realized. Severe potential still looks the best associated with
the northern complex that clips far northeastern zones. Will continue
to monitor trends closely this afternoon.


Short term...(today through thursday)
issued at 200 am MDT Tuesday Jul 22 2014

Continued warm today though not as hot as Monday for most areas.
Forecast challenges deal with temperatures and chances for severe
convective thunderstorm in the short term.

Currently...latest water vapor imagery showing dry slot that was
over the area Monday moving off to the east into central Nebraska
and South Dakota this morning. Some moisture to the west of this
dry slot over the western half of Wyoming into Carbon and Converse
counties early this morning. Mosaic radar showing some convection
developing in Natrona and Sweetwater counties early this morning.
Will need to watch this convection and update early probability of precipitation if it

For today...precipitable water forecasts continue to rise through
the day. NAM soundings showing Cheyenne precipitable waters at .5 inches at 12z
this morning...increasing to .86 inches by 00z. Precipitable waters in the
Panhandle increase up to 1.3 inches up by Chadron. Original
thinking was that warm middle level temperatures would cap any
convection this afternoon. That will be the case for most of the
day...but there is a period from 21z through maybe 02-03z where
soundings become uncapped...especially out in the Panhandle and
down here near Cheyenne. Went ahead and added some slight chance
probability of precipitation for the south Laramie range and for Niobrara well
as the northern Panhandle. With cape approaching 2000 j/kg out
near Chadron this afternoon...went ahead and added some severe
wording in the forecast as well. Can not rule out severe
thunderstorms here around Cheyenne either as NAM forecast cape
approaches 1500 j/kg. Will add in the severe weather potential statement for possibility of a few
severe thunderstorms.

Best chances for severe thunderstorms still looks to be Wednesday.
NAM sbcapes up near 4500 j/kg out in the Panhandle and for extreme
southeast Wyoming. Went ahead and added severe thunderstorms into
the Wednesday afternoon/early evening forecast for areas east of
the Laramie range.

Long term...(thursday night through monday)
issued at 255 am MDT Tuesday Jul 22 2014

Models generally in good agreement through the weekend...but there
are discrepancies between the European model (ecmwf) and GFS regarding available
low to midlevel moisture Sunday and Monday. Strong upper level
high will remain nearly stationary across The Four Corners region
through next weekend...and actually build northward again by late
in the weekend and early next week. Monsoon moisture will be in
the general area. Therefore...can not rule out afternoon showers
and thunderstorms each day. For Friday and Saturday...the upper level
flow will become more zonal as the dominant upper level high
drifts southward. This will allow a weak Pacific cool front to
push across the area with temperatures around 5 to 10 degrees
cooler on Friday and Saturday. This will allow some of the
monsoon moisture to be pushed southward into Colorado for the
weekend. Kept a slight chance of thunderstorms in the forecast for
now...mainly south. Overall...looks like a pleasant weekend with
highs in the middle 80s to middle 90s. Warmest temperatures will be over
western Nebraska.

By Sunday...models indicate a stronger front moving southward
across the High Plains with temperatures lowering into the low to
middle 80s during the day and generally below normal for this time of
the year. The European model (ecmwf) is more aggressive with shower and tstorm
activity each day through early next week as the front stalls near
the Laramie range...providing an area of natural low level
convergence. For some reason...the GFS is not showing a similar
solution and is mainly dry with a drier boundary layer. Since this
time of the year is dominated by a monsoon pattern...prefer the
European model (ecmwf) solution and increased pop between 20 to 35 percent just
north of the Colorado border towards the North Platte River


Aviation...(for the 18z tafs through 18z Wednesday morning)
issued at 1143 am MDT Tuesday Jul 22 2014

VFR conditions through the taf period. Winds will turn to the
southeast this afternoon but gusts should generally remain below 20
kts. While much of the area will not see storms this afternoon and
evening...isolated thunderstorms will be possible across the northern
Nebraska Panhandle...mainly from 01-05z. Gusty winds and brief
heavy rain will be the main threats from these storms.


Fire weather...
issued at 200 am MDT Tuesday Jul 22 2014

Continued dry today with afternoon humidities falling to 10
percent or less west of the Laramie range. Good news though is
that winds should not be as high today. So fire weather conditions
should be low today. A weak cold front will push into the
Panhandle and to the east slopes of the Laramie range this
afternoon...turning winds more north and northeasterly and weaken
the southwest winds west of the Laramie range. Areas east of the
Laramie range should see increasing chances for wetting rains
Wednesday as low level moisture pools into the area with the
easterly winds. Some monsoonal middle and upper level moisture will
move in as well humidities should be increasing
across southeast Wyoming into Thursday. Gusty westerly winds
return for Friday as low pressure tracks across Montana. Will see
a return of elevated to critical fire weather conditions Friday
into the weekend.


Cys watches/warnings/advisories...


short term...claycomb
long term...tjt
fire weather...claycomb

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