SPC Apr 26, 2017 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0243 PM CDT Wed Apr 26 2017

Valid 262000Z - 271200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE LOWER MS VALLEY...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER MS
VALLEY NORTH INTO SOUTHWESTERN IN...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
THE MID AND LOWER MS VALLEY...

...SUMMARY...
Severe thunderstorms will continue across the Lower Mississippi
Valley.  Tornadoes, large hail, and damaging winds are most probable
from northeast Texas across parts of Arkansas and northern Louisiana
this afternoon and evening. Isolated severe thunderstorms may extend
as far north as Illinois/Indiana this afternoon and evening, and
into the central Gulf States during the overnight hours.

...20Z Update...

...Lower MS Valley...
Outflow boundary continues to surge eastward across northern and
central AR ahead of the approaching cold front. Anafrontal character
to the ongoing convection is expected to continue with the cold
front eventually catching up to the outflow later this
afternoon/evening. Farther south, a more composite outflow/cold
front already exists with some severe storms currently ongoing.

Linear nature of this convection is expected to persist throughout
the evening with little indication in either recent observations
(i.e. backed mid-level flow on the 18Z SHV sounding) or recent
guidance that robust discrete development will occur.  As a result,
reduced the tornado probabilities across the area to 10%. Given the
strength of the shear, some QLCS tornadoes are still possible.

Strongest storms are expected to remain along the southern end of
the line where the best low-level moisture exists and the mean flow
is more orthogonal to the advancing cold front. 

...OH Valley...
Based on current convective trends, expanded the Slight a bit more
northeastward into more east-central IL and southwest IN.

..Mosier.. 04/26/2017

.PREV DISCUSSION... /ISSUED 1127 AM CDT Wed Apr 26 2017/

...Lower MS Valley...
Few changes have been made to the ongoing forecast.  A squall line
currently extends from south-central MO into northeast TX.  Several
bowing structures along this line will pose a risk of damaging winds
gusts, large hail, and perhaps a QLCS tornado or two this afternoon.
The activity will likely spread into southeast MO and western KY/TN
by early evening, with a continued severe threat.

Farther south, most model solutions suggest that the capping
inversion will slowly weaken this afternoon.  This should help to
allow a few discrete storms to form in the warm sector ahead of the
more organized convective line.  Local VAD and forecast hodographs
in this region continue to support a risk of supercells capable of
tornadoes (some strong) if discrete initiation materializes. 
Therefore will maintain the MDT risk and 15% tornado forecast. 
These storms are expected to track northeastward through the evening
into western/central MS where damaging winds and isolated tornadoes
will remain possible.

Overnight, it is uncertain how far east the organized severe threat
will persist.  Nevertheless, will make no changes to the eastern
extent of the SLGT risk at this time.

Read more

from SPC Forecast Products http://ift.tt/u32qoI