- Day Three
acus01 kwns 271959
Storm Prediction Center ac 271957
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0257 PM CDT Monday Apr 27 2015
Valid 272000z - 281200z
..there is a slight risk of severe thunderstorms from north-central Texas to the central
..there is a marginal risk of severe thunderstorms surrounding the slight risk
over the general area...
..there is a marginal risk of severe thunderstorms for portions of central and southern
Isolated strong to severe storms with hail...locally damaging
wind...and perhaps a tornado or two may affect parts of
north-central into eastern Texas and perhaps southwest Louisiana. A
few strong to possibly severe storms also may occur over central and
The only substantial changes this outlook update include...
1) the removal of 5 percent tornado probabilities over southeastern la. The
early day mesoscale convective system has moved into the Gulf and the airmass has become
less unstable in its wake. Another round of storms is expected to
move into southeastern la later today/tonight and strong wind profiles will
support a conditional severe threat for organized storms.
2) added low severe probabilities for much of the southern half of the Florida
Peninsula as recent iterations of convection-allowing models show
the northern Gulf of Mexico mesoscale convective system continuing east-southeastward and affecting the Florida
Previous discussion... /issued 1118 am CDT Monday Apr 27 2015/
A middle to upper-level low will edge slowly eastward across the Southern Plains
in response to an amplifying upstream ridge over the Great Basin
into northern rockies. A middle-level jet streak observed within the base
of the upper low per 12z observed soundings will progress generally
eastward into the central Gulf Coast.
At the surface...an area of low pressure over north-central Texas will
develop southeastward into southern la along a cold front advancing southeastward through
central and southern parts of Texas. Meanwhile...visible satellite and
surface observations as of middle morning indicate an outflow boundary
associated with the Bow echo over southeastern la extending westward through the
Upper Texas coast before curving nwwd along a baz-Sep line where it
links with the surface low and associated cold front.
..sern Texas into the central Gulf Coast today into tonight...
A well-defined Bow echo with a history of fairly widespread damaging
winds should continue east-southeastward through the remainder of far southeastern la
late this morning into early afternoon with a risk for damaging
winds and perhaps a tornado or two over those locations. In the
wake of this mesoscale convective system...it appears that warm air advection/isentropic ascent atop the
trailing outflow boundary coupled with deeper-layer forcing for
ascent related to the above-mentioned middle-level jet streak may
support the development of thunderstorms this afternoon into tonight from
southeastern Texas eastward into la.
Based on the 12z soundings at crp and bro...ample low-level moisture
surmounted by a well-defined eml will support moderate afternoon
instability and the potential for organized storm modes including
supercells given 40-50 knots of deep-layer shear. While large hail
appears to be the primary hazard...locally damaging winds and
perhaps a brief tornado or two are possible.
..N-central into eastern Texas this afternoon/evening...
As mentioned above...considerable overturning of the air mass has
occurred over eastern into north-central Texas in the wake of the mesoscale convective system now over
la. However...cold middle-level temperatures coupled with a warming
boundary layer should support air mass destabilization by afternoon
ahead of the surface low and cold front with MLCAPE approaching
1000-1500 j/kg. Forcing for ascent in advance of the deep-layer
cyclone is expected to Foster the development of surface-based
storms by afternoon amidst a kinematic environment featuring
vertically veering and strengthening winds with height. As
such...supercells are possible with the risk for large
hail...damaging winds and a couple of tornadoes spreading southeastward into
parts of eastern Texas. This severe weather threat should begin to wane by
middle to late evening as the boundary layer begins to cool and
..FL peninsula this afternoon...
Pronounced westerly deep-layer flow observed by 12z soundings will
persist today with diurnal storm development likely remaining
confined to the East Coast sea breeze. While middle-level lapse rates
will remain poor...daytime heating coupled with a moist boundary
layer will yield moderate afternoon instability and the potential
for a few strong to marginally severe storms this afternoon with a
risk for locally damaging wind gusts.
acus11 kwns 272140
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 272140
Mesoscale discussion 0484
National Weather Service Storm Prediction Center Norman OK
0440 PM CDT Monday Apr 27 2015
Areas affected...cntrl/srn Florida Peninsula
Concerning...severe potential...watch unlikely
Valid 272140z - 272245z
Probability of watch issuance...20 percent
Summary...a localized hail/wind threat will exist across eastern
portions of central/South Florida over the next couple hours. A ww is not
Discussion...strong diurnal heating has occurred across central/southern Florida
with temperatures near 90 f in many locations amidst middle-60s to
middle-70s surface dewpoints. This has yielded sufficient buoyancy to
support strong thunderstorm development in spite of warm midlevel
temperatures. Currently...the strongest thunderstorm is moving across
Highlands/Okeechobee counties...which formed along a synoptic cold
front. 50-60 knots of effective shear is supporting marginal supercell
structures with this storm...which has a history of producing
one-inch hail. Other thunderstorms are developing farther S between mia and
pbi along a westward moving sea breeze boundary. Here...thunderstorms will have a
short residence time over land given Ely motion...but brief hail and
strong wind gust potential may exist. A brief/weak tornado threat
could exist if the sea breeze boundary can interact with more
organized convection farther inland. The isolated nature of these
threats will preclude ww issuance.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 25098037 25238081 26248107 27518120 28028088 28128051
27608021 26557990 25638007 25098037