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Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO
617 am CDT Tuesday Aug 4 2015

Discussion...
issued at 439 am CDT Tuesday Aug 4 2015

A broken line of convection, stretching from the northwest tip of
Missouri east southeast through Macon overnight, developed a bit
before midnight across far northern Missouri. This convection seems
to be finding life with the help of the entrance region of 90+ knot
300mb polar jet, located just to our northeast, along with the exit
region of a more modest sub-tropical jet stretched across the Central
Plains, which in turn owes its existence to the shortwave trough
currently ridging its way up and over the ridge axis across the Rocky
Mountains. Add to this a modest 20 knot southwest low level jet
interacting with an elevated boundary across northern Missouri under
the divergent flow aloft, and you get the ingredients for a series of
training thunderstorms.

Model solutions have not been the best at handling the details of
this mornings convection, but they generally agree with the main
trend. The convection is expected to persist through sunrise as the
moisture transport with the nocturnal jet persist, with storms
generally training along the same track across northern Missouri
through the mid-morning hours until the divergent flow aloft and
modest moisture transport finally move off and/or weakens. So, for
this morning expect storms to keep percolating across northern
Missouri, fading through the late morning to early afternoon hours.
The lack of shear should keep the storms from getting too strong and
producing severe weather, but torrential rain and flash flooding
could be an issue in areas where the storms repeatedly track this
morning.

This afternoon a bit of energy in the base of the shortwave trough,
that is riding up and over the Rocky Mountain ridge, is expected to
Peel off and continue east across the plains states. Currently there
is enough lift within this perturbation to induce convection across
the Panhandle of Texas into western Oklahoma this morning, and that
trend is expected to persist through the morning and into the
afternoon hours. This should bring more storms into eastern Kansas
and Missouri from the west and south, possibly as early as the late-
afternoon hours. Storms will be likely by this evening as the parent
perturbation keeps moving east. The severe threat from storms this
afternoon and this evening looks marginal at best as shear values
advertised are rather low, with 0-6 km shear values under 25 knots
tonight. However, precipitable water values will be well above normal
again, thus likely leading to more flooding issues where the storms
persist for more than an hour or two. Have held off any Flash Flood
Watch at this time owing to extremely low confidence on where
tonight's convection will set up, as current model solutions indicate
that areas from east central Kansas into central Missouri may get a
lot of rain while areas of far northern Missouri might get next to
nothing, which would be a reverse from what has been happening over
recent nights with storms across far northern Missouri.

For Wednesday...there is considerable potential that storms might
keep-on-keeping-on from Tuesday night into Wednesday. Tuesday night,
as the perturbation moves across Missouri, the larger parent
shortwave trough will be sliding southeast in a northwest flow. This
larger trough will generate convection of its own across the
northern plains late tonight which will track southeast in our
direction. Currently expect some kind convective complex to develop
from this and track into eastern Kansas and Missouri Wednesday, thus
keeping storms likely across parts of the region into the day
Wednesday. Severe potential for the continuing storms Wednesday is a
bit nebulous at this time owing to all the antecedent storms that
will have already affected the region, but in general expect shear
values to increase as the parent shortwave drops into Missouri within
the northwest flow. Currently, large hail, damaging winds and
torrential rain all look possible with storms through the day
Wednesday.

Conditions should then dry out some Thursday as the ridge to our
west expands east into Missouri, which should help lift temperatures
back to around normal for this time of year. However, pops will
quickly ramp back up as we move towards and through the weekend as
another large trough moves east along the Canadian border. Model
solutions in this time frame continue to indicate on-again-off-again
storm chance as a result for Friday and through the weekend.

&&

Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 616 am CDT Tuesday Aug 4 2015

VFR conditions will dominate the terminals through much of the next
24 hours. Morning convection across far north Missouri looks to stay
clear of the terminals during the day. There is a chance that the kstj
site might have some vicinity storms through the mid to late morning
hours from activity sliding southeast from Nebraska. Otherwise, will
likely need to wait till the late afternoon or early evening hours
for storms to redevelop, moving in from the southwest. Confidence on
when these storms will develop is low, but have highlighted the
hours thought to have the greatest threat for storms with a tempo
group this evening. Otherwise, expect wind to remain generally at or
below 10 knots from the south to southeast.

&&

Eax watches/warnings/advisories...
Kansas...none.
MO...none.
&&

$$

Discussion...cutter
aviation...cutter

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