U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 261254 
Storm Prediction Center ac 261253 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0753 am CDT sun Mar 26 2017 

Valid 261300z - 271200z 

..there is a moderate risk of severe thunderstorms south-central OK 
and far north-central Texas... 

..there is an enhanced risk of severe thunderstorms central/east OK 
into far North Texas... 

..there is a slight risk of severe thunderstorms far south 
Kansas...west Arkansas...and north-central Texas... 

..there is a marginal risk of severe thunderstorms parts of 

..there is a marginal risk of severe thunderstorms upper Ohio 

Numerous severe storms with very large hail, tornadoes, and damaging 
winds are expected after 4 PM CDT across central and eastern 
Oklahoma into northeast Texas through this evening. 

A compact shortwave trough over southeast Colorado will track towards the 
Ozark Plateau through early Monday. Attendant surface cyclone will 
become established across west-central/northwest OK by 00z, with the 
dryline south through central Texas and a quasi-stationary front 
extending northeast to the Ozarks. 

..southern Great Plains... 
Poleward advection of a Gulf moisture plume sampled by 00z Corpus 
Christi and Lake Charles raobs has occurred overnight in southern to 
central Texas with the leading edge of 60 degree f surface dew points 
reaching about 31 degree north latitude as of 12z. This plume will 
continue to advance north beneath the elevated mixed-layer across 
North Texas into OK. The rap has consistently been most aggressive with 
the spatial extent and amplitude of boundary-layer moisture 
returning into central and eastern OK by evening. Robust surface 
heating of this moisture plume will contribute to 1000-2500 j/kg 
MLCAPE by 00z. As the dryline mixes east towards the I-35 corridor 
and convergence along it increases, initial storm development is 
expected about 21-22z from near the surface cyclone southward into 
far north-central Texas. Within a swath of 50-60 kt 500-mb 
southwesterlies, this setup should favor discrete supercell 

Primary uncertainties beyond the degree of boundary-layer moisture 
are the overall number of storms as well as the southern extent of 
sustained supercell development in Texas prior to increasing mlcin 
after sunset. Many hrrr and hrrr-esrl runs have been consistent in 
suggesting potential for several discrete storms versus other cams 
which only have a few. Given the environmental setup which should 
promote hail growth beyond 2 inches in diameter in most supercells, 
the compact nature of the shortwave trough and associated forcing 
for ascent, along with relatively high confidence in placement of 
synoptic features, an upgrade to moderate risk for hail appears 

Enlarged low-level hodographs owing to a 40-kt southerly jet suggest 
that a few supercells along the southern periphery of development 
should pose an enhanced risk for tornadoes in the 23-03z time frame. 
Evolution of discrete supercells into a bowing cluster may also 
occur as the low-level jet intensifies, yielding an enhanced risk 
for intense damaging wind gusts centered on southeast OK. 
Warm-sector activity should wane overnight as it spreads into Arkansas 
amid weakening instability. 

..upper Ohio Valley... 
A shortwave trough along the Iowa/Illinois border will shift towards the 
lower Great Lakes. Abundant cloud coverage downstream of this wave 
will limit the degree of destabilization given a warm-sector 
moisture plume characterized by only lower to middle 50s surface dew 
points. This should result in meagerly buoyant profiles with MLCAPE 
of 250-500 j/kg. Most cams suggest scattered convection 
mid-afternoon to early evening. With moderately strong 700-500 mb 
wind fields, a few multicell clusters may pose a risk for isolated 
damaging winds. 

.Grams/Gleason.. 03/26/2017 


Mesoscale Discussion

acus11 kwns 260628 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 260628 

Mesoscale discussion 0332 
National Weather Service Storm Prediction Center Norman OK 
0128 am CDT sun Mar 26 2017 

Areas affected...the Upper Peninsula of Michigan 

Concerning...freezing rain 

Valid 260628z - 261200z 

Summary...freezing rain rates around to slightly above 0.05 inch per 
3 hours will be possible through 12z. 

Discussion...within a region of low-level warm air advection across 
much of the Great Lakes and ahead of an approaching upper-level low 
over the mid MS valley, light to locally moderate freezing rain 
rates will be possible, mainly across parts of the Upper Peninsula 
of Michigan. Radar imagery shows light precipitation over the Upper 
Peninsula as of 0615z, with a mix of rain/freezing rain farther 
south across northern lower Michigan per surface observations. A residual 
dry low-level airmass will support surface temperatures falling 
below freezing, as wet bulb temperatures generally range from 26-32 
degrees f. As the plume of higher reflectivity with greater 
precipitation rates moves northward across the Upper Peninsula, 
freezing rain rates should likewise increase, with various 
short-term high resolution guidance suggesting rates at or slightly 
above 0.05 inches per 3 hours becoming common. A longer duration of 
freezing rain may be possible across the far Eastern Upper Peninsula 
(chippewa/Mackinac counties), where lower surface wet bulb 
temperatures will support freezing rain through the early morning 
hours. Elsewhere, freezing rain should slowly transition to mainly 
rain from south to north through 12z as continued low-level warm air 
advection encourages surface temperature to rise above freezing. 

.Gleason.. 03/26/2017 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 45908340 45738440 46008540 45908666 46048785 46168870 
46348893 46878847 46988810 46828495 46268354 45908340