SPC MD 1454



MD 1454 CONCERNING SEVERE POTENTIAL…WATCH LIKELY FOR PORTIONS OF WESTERN AND CENTRAL MONTANA

MD 1454 Image

Mesoscale Discussion 1454
NWS Storm Prediction Center Norman OK
0206 PM CDT Sat Jul 13 2019

Areas affected...portions of western and central Montana

Concerning...Severe potential...Watch likely 

Valid 131906Z - 132100Z

Probability of Watch Issuance...80 percent

SUMMARY...Storm coverage will increase this afternoon across
portions of western and central Montana. Damaging winds and large
hail are the main severe threats and a watch issuance is likely.

DISCUSSION...An upper-level shortwave trough is moving over the
Pacific Northwest and northern Rockies today helping to provide
forcing for ascent across the region. Elevated storms have continued
over the northern Rockies since early this morning and current
satellite/radar imagery show signs of convective initiation and
intensifying storms. The airmass is becoming increasingly unstable
per mesoanalysis and the 18z TFX sounding due to steepening
mid-level lapse rates (7.5+ C/km) and daytime heating, and a 40-50+
knot mid-level jet is approaching western Montana with effective
bulk shear currently around 35-40 knots per mesoanalysis. MLCAPE
will increase throughout the afternoon likely approaching 2000 J/kg,
and shear will continue to increase as the mid-level shortwave
trough/jet approaches.

Supercells are likely to develop initially, but given the strong
forcing for ascent, storms are expected to grow upscale into loose
multicell clusters. Large hail is likely, especially with any
supercell that develops, and damaging wind gusts are also likely
with steep low-level lapse rates (9+ C/km), relatively high LCLs
(2.5-3 km AGL), and strong winds through the vertical profile. A
severe thunderstorm watch issuance is likely due to these severe
threats.

..Nauslar/Thompson.. 07/13/2019

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

ATTN...WFO...BYZ...TFX...MSO...

LAT...LON   45331060 45131170 45701247 46631305 47391312 47931283
            48271221 48721124 48911027 48560983 47270923 45830915
            45550950 45331060 

Read more



Source link

  • Editor