Mesoscale Discussion 86

Issued

Feb 15, 2021, 5:57 AM CST (11:57 UTC)

Expired

Feb 15, 2021, 12:00 PM CST

In force

6 hr

Issued by

the Storm Prediction Center

Concerning

Heavy snow

The Memphis radar (KNQA), 80 km from the middle of the area, began a volume at 12:02 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

659 
ACUS11 KWNS 151157
SWOMCD
SPC MCD 151157 
KYZ000-TNZ000-ILZ000-MSZ000-MOZ000-ARZ000-LAZ000-151800-

Mesoscale Discussion 0086
NWS Storm Prediction Center Norman OK
0557 AM CST Mon Feb 15 2021

Areas affected...eastern half of AR...northwest MS...western
TN...southeast MO...western KY

Concerning...Heavy snow 

Valid 151157Z - 151800Z

SUMMARY...Heavy snowfall rates around 1 inch per hour (locally
around 1.5 inch in heavier bursts) are likely to develop
northeastward across the lower MS Valley into the lower OH Valley
through noon CST.

DISCUSSION...Radar mosaic shows a large precipitation shield early
this morning over the Arklatex moving northeast.  A powerful
mid-level trough over the southern Great Plains, evident on
water-vapor imagery, will continue to move east towards the lower MS
Valley this morning.  

SREF-based 1 inch-hour snowfall rates have corroborated well with
surface observations over northeast TX/northwest LA early this
morning (e.g., Henderson, TX; Shreveport, LA).  The model guidance
suggests the heavier snowfall will spread downstream into eastern AR
through mid morning.  The strong large-scale ascent, implied by an
expanding mid-level moisture plume, will overspread the lower MS
Valley through mid morning and towards the OH/MS River confluence
during the 10am-12pm period.  Intensifying snowfall rates will
correspondingly occur as the stronger ascent spreads downstream into
the greater Memphis area (9am-12pm) with heavy snowfall rates
maximizing during the mid-late morning.  Forecast soundings indicate
a sleet or mix of sleet/snow precipitation type before changing to
snow for parts of northern MS and western TN.

..Smith.. 02/15/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...OHX...PAH...MEG...JAN...LSX...LZK...SGF...

LAT...LON   34679276 36639196 37508993 37408761 36988746 34428928
            32889098 32979182 33809277 34679276

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.