Area Forecast Discussion
Issued by NWS Springfield, MO
FXUS63 KSGF 220334 AAC
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1034 PM CDT Tue Apr 21 2015
...Updated Mesoscale Discussion...
Issued at 1034 PM CDT TUE APR 21 2015
First batch of storms has weakened and exited to the southeast. We
are not done, however as additional scattered showers are
developing across the Hwy 60 corridor. This is ahead of a fast
moving cold front that is just about to enter the far northern
chimney of Morgan county.
Deep layer shear does remain quite strong, in excess of 40kt. As
one would expect given loss of solar insolation, what little
instability we had earlier has lessened even further. Surface
based CAPE is almost non-existent, mixed layer CAPE is in the
100-200 J/kg range and most unstable CAPE is in the 250 to 500
J/kg. In spite of the lack of quality CAPE, forcing and shear
will be strong enough to support elevated scattered shower and
thunderstorm development ahead of the cold front and along the
850mb front (which lags behind the surface cold front) for the
rest of tonight. Given the lack of quality CAPE, it will likely
be tough to get severe hail. Given such cold mid level
temperatures, just about any updraft will produce some pea sized
hail, but the more "robust" updrafts will be briefly capable of
producing hail to the size of pennies.
For the time being, have gone with scattered activity the rest of
tonight, but will increase PoPs if there is a preferred zone of
development that shows its cards.
.SHORT TERM...(This Evening through Wednesday)
Issued at 248 PM CDT TUE APR 21 2015
Gusty west to southwesterly winds will continue through the reminder
of the afternoon hours...but will gradually weaken into this
Scattered thunderstorms are starting to develop across portions of
west central MO into the eastern Ozarks. These storms are developing
as lift from an upper level low over the great lakes region
interacts will weak instability that is developing with day time
heating and low level moisture advection. The upper level low is
spreading increased wind shear and colder temperatures in the mid
levels. So, it won`t take much of an updraft to get a small hail out
of storms. Instability will remain on the weak side and wide spread
severe weather is not expected, but a few of the stronger storms
could produce hail up to the size of quarters and winds over 50 mph.
These storms will generally occur along and northeast of a Lamar to
Springfield to West Plains MO line and will push southeast of the
area this evening.
Later this evening into tonight additional isolated to scattered
storms will be possible as a cold front sags south through the area.
Instability will remain on the weak side with small hail and cloud to
ground lightning strikes being the main risk with these storms.
On Wednesday 500mb low lifts northeast of Lake Superior but
cyclonic flow continues over Missouri. At the surface high pressure
noses southward into northern Missouri while residual boundary slips
south into Arkansas. This will keep the area with below normal
temperatures with highs only in the 50s and 60s. Models consistent
in weak isentropic lift north of the boundary into southern Missouri
at least early on Wednesday with enough lift for some
showers/storms, especially over far southern Missouri. Best
instabilities remain south of the forecast area with only 300 j/kg
of most unstable cape early in the day along the Arkansas border.
Tapered probabilities from north to south. There could be some
showers across far southern Missouri Wednesday night, otherwise dry
conditions will be seen.
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 248 PM CDT TUE APR 21 2015
Shortwave ridging builds across the area Thursday suppressing any
showers to the south near the Arkansas border during the morning
hours. The next shortwave will lift out of the desert southwest
into the central/southern plains Friday and across Missouri on
Saturday. Although there are some model differences with respect
to the track of the surface low, the Friday time frame looks to be
the best chances for showers and storms, with Saturday more
showery as system begins to pull east of the area. Weak high
pressure will move in Saturday night and into Sunday giving
everyone a break from the rainy weather. However, next shortwave
will drop across the plains around another deep 500mb low over the
Great Lakes. This will bring rain chances back into the forecast
for late Sunday into Sunday night and then pushes east Monday.
Some low probability rain chances on Monday and Tuesday with hard
time shortwave energy in fast flow aloft.
Temperatures look to remain on the cool side through much of the
period with highs in the 60s and lows in the 40s. At this point it
looks like there is minimal frost potentials.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 731 PM CDT TUE APR 21 2015
Scattered thunderstorms will continue to move southeast through
southern Missouri early this evening. At this time it appears that
this activity will miss BBG to the east, but will closely monitor
over the next hour or so. Otherwise, there will be a break in the
action until the overnight hours when scattered showers and storms
will redevelop along a cold front moving in from the northwest.
Coverage again looks scattered and will hone in on timing of this
activity with future updates. Winds will shift to the north late
tonight with the frontal passage. Overall, mainly VFR conditions
are expected, with mainly mid/high level clouds expected.