Mesoscale Discussion 39

Issued

Jan 13, 2017, 10:28 AM CST (16:28 UTC)

Expired

Jan 13, 2017, 4:30 PM CST

In force

6 hr

Issued by

the Storm Prediction Center

The Springfield radar (KSGF), 31 km from the middle of the area, began a volume at 16:30 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.

738 
ACUS11 KWNS 131629
SWOMCD
SPC MCD 131628 
INZ000-ILZ000-MOZ000-KSZ000-OKZ000-132230-

Mesoscale Discussion 0039
NWS Storm Prediction Center Norman OK
1028 AM CST Fri Jan 13 2017

Areas affected...Portions of southwest IN...southern
IL...southern/central MO...southeast KS...OK

Concerning...Freezing rain 

Valid 131628Z - 132230Z

SUMMARY...An extensive corridor of freezing-rain potential will
continue through the day from portions of OK to parts of the lower
OH Valley.

DISCUSSION...A persistent plume of elevated warm advection and
moisture transport will continue to foster an extensive corridor of
precipitation potential through the day -- from portions of OK to
parts of the lower OH Valley. With the 12Z Norman OK, Springfield
MO, and Lamont OK soundings sampling maximum elevated warm-layer
temperatures around 9C-12C, complete melting of descending
hydrometeors will occur prior to their contact with the subfreezing
surface layer. Meanwhile, subfreezing surface temperatures from
parts of southwest OK to southwest IN will be reinforced by
continued cold advection within the surface layer -- reflected by
modest pressure rises on the order of 0.5-2.0 mb per 2 hours. As a
result, the risk for freezing rain will continue through the day,
with freezing-rain rates around 0.02-0.08 in/hour -- locally higher.

The greatest coverage and intensity of freezing rain should remain
concentrated within a corridor from far northeast OK and southeast
KS east-northeastward through parts of south-central MO and into
southwest IL. This is where (1) isentropic ascent aloft should
remain strongest, and (2) generating convective elements from the
southwest will likely reach maturation stages while congealing.
Furthermore, marginal (though non-zero) elevated buoyancy -- rooted
within the elevated warm layer -- was sampled by the aforementioned
soundings. This will offer some convective enhancement to
freezing-rain rates, along with continued lightning potential
accompanying the heaviest freezing rain. Slight northward spread of
this precipitation shield may occur through the day, in tandem with
the motion of the warm-advection zone.

Eastward from the greatest coverage/intensity corridor into
southwest IN, weaker ascent should tend to mitigate overall
freezing-rain intensity to some extent. However, the influx of
precipitation generated upstream, atop sub-freezing wet-bulb surface
temperatures, suggests light freezing rain will be possible.

Areas well southwestward into parts of north-central, central, and
southwest OK will be a region of development of convective elements
(as indicated by recent mosaic radar loops). Ascent -- albeit
relatively more modest -- should be sufficient for widely scattered
coverage of freezing rain showers through the day. The influx of
moderate midlevel lapse rates (sampled by upstream AMA/MAF
soundings) suggests that some convective enhancement will accompany
this activity. This should yield brief instances of light to
occasionally moderate freezing rain through the day.

..Cohen.. 01/13/2017

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

ATTN...WFO...LMK...IND...PAH...ILX...LSX...SGF...EAX...TSA...
ICT...OUN...

LAT...LON   36799477 35009797 34749918 35129952 36029900 37599563
            38759218 39178820 38878692 38258709 37628885 36799477

Mesoscale Discussions in Missouri, 2017Mesoscale Discussions in Illinois, 2017Mesoscale Discussions in Oklahoma, 2017Every mesoscale discussion in 2017

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.