Area forecast discussion
National Weather Service Topeka Kansas
637 am CDT Sat may 25 2013
Short term...(today and tonight)
issued at 400 am CDT Sat may 25 2013
On the water vapor imagery at 08z...a weak shortwave trough was
translating northeast through the dominant ridge axis over the
plains. Surface observations indicate the surface low centered over
eastern Colorado as a warm front stretched from central Kansas
through Oklahoma gradually shifting eastward through the overnight
period. Energy from the shortwave aided by a 50 knots low level jet developed an
mesoscale convective system over Nebraska which has been slowly weakening as it shifts
towards the east southeast.
Corfidi vectors directed towards the east southeast should bring
this weakening mesoscale convective system and associated outflow boundary across the
northern forecast area during the morning hours Saturday. Weak middle level
instability should greatly weaken this complex with perhaps a few
lingering thunder showers. Forecast for the remainder of the day is
quite tricky as models are handling precipitation quite poorly with
an array of boundaries in the area to trigger convection. The latest
NAM/rap/ECMWF/hrrr are in somewhat agreement that the highest
chances for thunderstorms reside over the far northern counties of
northeast Kansas. The warm front is prognosticated to setup near the Kansas
Nebraska border with another weak shortwave shifting over southern
Nebraska. In addition a lingering outflow boundary from overnight
convection may establish enough of a trigger combined plenty of
moisture and warm air in place. The main hindrance is the decent
capping inversion in place which may inhibit development until the
afternoon period...if any with no strong middle level lift. Overall
maintained a low chance of precipitation as most of the afternoon should be
rain free with mostly cloudy skies. The deepening surface low over
eastern Colorado should also increase warm air advection and southwest flow during
the afternoon with highs in the low 80s.
A similar scenario sets up on Saturday evening with a series of
minor shortwave troughs shifting over northern Kansas into Nebraska.
Most of the models agree on developing another mesoscale convective system over
Nebraska/northern Kansas during the overnight period. While elevated
instability is available...weak shear values should inhibit severe
potential. Overnight lows remain mild in the low to middle 60s.
Long term...(sunday through friday)
issued at 400 am CDT Sat may 25 2013
The bulk of the next several days will be warm...breezy/windy...and
more humid that the bulk of the Spring so far. Precipitation chances
remain the primary challenge...with little in the way of specifics to
nail down confidence.
Persistent weak middle level warm air advection under the mean ridge
will serve to keep some capping in place through at least middle week.
There is some agreement in shortwaves moving through the flow late
Sunday and again late Monday...though at this point timing and
strength of these features is lacking...and their ability to break
down the cap is in question. Deep layer shear also will not be
impressive...and previous thoughts on the low likelihood of
widespread severe weather stand. At this point have higher
confidence in precipitation Sunday night with some evidence of low
level Theta-E advection being above to reduce the somewhat weaker
cap. Overall did reduce probability of precipitation a bit for these periods given the
capping. With a tight gradient and 850/925mb wind speeds in the
50/40kt range respectively...winds could near advisory levels if any
stratus is not too prevalent.
The Tuesday to at least early Wednesday periods are still on track
for the most likely dry periods. Models are similar with expansive
westerlies over the Pacific pushing in to the southern rockies and
eventually the plains in the late Wednesday into Friday
periods...but differences remain on timing and character of waves
moving through this flow. Bulk shear will be boosted with higher
chances for the waves to knock down the cap for greater severe
weather potential. Depending on mesoscale evolution...the southwest
flow could persist for multiple rounds of precipitation in the late week.
&&
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 615 am CDT Sat may 25 2013
Tracking remnant MVFR stratus as it dissipates ahead of a warm
front at ktop/kfoe/kmhk. Cluster of thunderstorms and rain near Kansas and Nebraska
border will remain north of sites as it shifts eastward. VFR
prevails after 14z at kmhk and 15z ktop/kfoe as southerly winds gust
at or above 20 kts. Slight possibility for convection developing near
terminals overnight Saturday...however low confidence left no
mention in tafs at this issuance.
&&
Top watches/warnings/advisories...
none.
&&
$$
Short term...Bowen
long term...65
aviation...Bowen
