Severe Weather Discussion for April 6, 2010.
– Isolated severe thunderstorms are possible across northeast Oklahoma
on Sunday. Primary threat is large hail.
– Severe thunderstorms are possible across central/eastern Oklahoma on
18z models indicates decent moisture return on Sunday, south of a
developing warm front. Moisture values of around 60F will be present
in much of Oklahoma. However, the favored area for development looks
to be northeast Oklahoma. This activity will not be significant as
instability will be AOB 1000 J/Kg CAPE. A slight risk is possible on
Sunday, even though SPC has it only to the KS/OK border.
SPC Day 4-8 highlights MO to WI on Tuesday and this appears to be in
error given latest guidance. While a medium-end event appears
questionable this far out, there several parameters favorable for
severe thunderstorms in Oklahoma. Moisture is currently returning
in-wake of Friday's system with low 60s expected by late Sunday. A
surface ridge will dominate much of the Gulf during the period, but
decent deep layer moisture will be in-place across Oklahoma on
Tuesday. Model progged temperatures yield CAPE values around 1500
J/Kg Tuesday afternoon. In general, wind fields look favorable for
organized severe thunderstorms across the state. The faster GFS shows
that CIN is minimized Tuesday afternoon as the upper system progresses
eastward. Models do vary significantly regarding the placement of
surface features with this system. GFS maintains a strong lead
shortwave trof, taking the surface low with it while the NAM is
farther west. ECMWF is somewhere in the middle. GFS was correct on
Friday's system, so may be important to give it a little more
consideration. Either way, the potential threat should be across
central/eastern Oklahoma. NAM shows a CAPE min in eastern Oklahoma
due to a 850mb moisture min. I'm not convinced this is correct and
for now will ignore it. Both models develop QPF along the dryline
late Tuesday afternoon into the evening hours.
00z NAM is similar to prior runs with the incoming upper system. It
also develops QPF around 00z late Tuesday just west of OKC. As noted
CAPE value are around 1500 J/Kg and some points are a little higher.
NAM has an odd 850mb dewpoint sink, which I have seen before. Given
the strong ridge near Florida, it could be true. However, at the
juncture it doesn't appear to influence things too much. Wind fields
should be quite sufficient for rotating storms. The 850mb/700mb look
a little low near the dryline at 00z but the NAM will under-forecast
Risk area for any part of OK (valid: 04/04 Day 3):
Level 1 – Normal
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