Mesoscale Discussion 310

Issued

Mar 23, 2017, 1:47 PM EDT (17:47 UTC)

Expired

Mar 23, 2017, 4:15 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

20%

The Tampa radar (KTBW), 145 km from the middle of the area, began a volume at 17:46 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.

381 
ACUS11 KWNS 231748
SWOMCD
SPC MCD 231747 
FLZ000-232015-

Mesoscale Discussion 0310
NWS Storm Prediction Center Norman OK
1247 PM CDT Thu Mar 23 2017

Areas affected...Central and southern Florida Peninsula

Concerning...Severe potential...Watch unlikely 

Valid 231747Z - 232015Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms will continue to increase in intensity and
coverage the next few hours but will pose a low threat for
marginally severe hail and brief wind gusts through the afternoon.

DISCUSSION...Widely scattered thunderstorms have percolated along
the east coast of the central and southern Florida peninsula through
the late morning hours ahead of a weak upper-level
perturbation...with one cell now showing some organization and weak
mid-level rotation moving southward into St. Lucie county. 
Mixed-layer CAPE of 500-1250 J/kg aided by mid-level lapse rates of
7.5-8 C/km...somewhat larger than typical for late March in southern
Florida...should continue to allow for updrafts strong enough to
support small hail production. Marginally severe hail and brief
severe wind gusts are possible in the strongest updrafts that show
some mid-level rotation.  

As low-level lapse rates steepen in afternoon heating, the larger
evaporative cooling should strengthen/amalgamate cold pools that
spread south and southwest to the Gulf of Mexico coast.  Weak wind
shear in the lowest 1 km directed toward the cold pool motion should
augment the tendency for cold pools to spread rapidly south and
west.  Although mean wind speeds are relatively weak, vertical bulk
wind shear magnitudes of 25-35 kt in the 1-8 km layer should
continue to support some thunderstorm organization for the expected
continuation of south-southwesterly storm motions.  Otherwise...the
primary mode will be multicellular/pulse in nature with storms
propagating somewhat discretely along the spreading cold pools.  The
intensity and coverage of the threat is expected to remain low
enough to prevent a watch.

..Coniglio/Hart.. 03/23/2017

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

ATTN...WFO...MFL...MLB...KEY...TBW...

LAT...LON   28038068 27508032 26548003 25708017 25258037 25148081
            25218109 25868156 26348204 26938234 27268249 27728256
            28138234 28308161 28278112 28038068

Mesoscale Discussions in Florida, 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.