Severe Weather Discussion for May 1, 2008.
– Severe thunderstorms are expected late this afternoon into the
overnight hours for central and eastern Oklahoma northward into Iowa.
Primary threats are large hail and damaging winds. An isolated
tornado or two can't be ruled out, especially in southeast Kansas.
No change to forecast thinking this go around. 12z models brought
back the double barrel surface low through 850mb. None of this really
matters as the overall setup is not favorable for a significant severe
weather event. Dewpoints have recovered nicely across the region with
SBCAPES around 3600 J/Kg but MLCAPE is around 2800 J/Kg. This is
reflection of the shallow nature of moisture return this afternoon.
Further, dewpoints in north Texas are in the low/mid 60s with tropical
moisture just north of Houston. Current thinking is that the high
octane moisture will not make it here in time for afternoon convection
and may only be creeping in here as the cold front overtakes the
dryline this evening.
As noted in prior discussions the upper level winds do not remain that
favorable for 1) convective initiation and 2) organized convection as
the 300mb-200mb jet streaks are displaced westward from the dryline
through early evening. Conditions should come together during the
evening hours as the cold front reaches the dryline, moisture
increases, and deep layer lift impinges on the region. A squall line
is expected with the potential for embedded supercells. The priamry
threats should be large hail and damaging winds. I'm not ruling out
an isolated storm around 6-7pm this evening on the dryline, but the
better chance is overnight with the squall line. The convective temp
this morning at Norman was 97F and I see little reason for this to
decrease. OUN will do a special sounding at 20z. SPC analysis from
18z shows MLCIN 25-100 J/Kg and this is expected given the strong cap
and meager moisture.
Level 1 – Normal
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