May 19, 2013
SHORT TERM [Friday Through Saturday Night]...
A progressive flow pattern will lead to rapid changes in the
weather over the short term period. Friday will begin with a ridge
of surface high pressure in the eastern United States, and a low-
amplitude shortwave trough quickly transitioning east across the
Southern Plains. Weak surface cyclogenesis will occur along the
Gulf Coast states from 12z Friday to 12z Saturday, with increasing
low-level WAA across our forecast area. 850-300mb QG convergence
and deep isentropic ascent (295-315K planes) becomes maximized
over our forecast area 06-12z Saturday. This is consistent with
model depictions of the highest PoPs, and also with the inherited
forecast trends. Therefore, very little changes were made to the
timing of rain in the forecast today, and there is still high
confidence in rain on Friday Night. 27.15z SREF probabilities of
MUCAPE exceeding 250 j/kg increase to 70-90% across the southern
and eastern portions of the area between 06z and 12z Saturday.
Therefore, a mention of isolated thunderstorms was maintained in
the forecast. Appreciable MLCAPE remains offshore on Friday Night,
so there isn`t much concern for severe weather at this time. CAA
sets in quickly in the wake of the cold front, with a freeze
possible Saturday Night, particularly in the northwest half of our
forecast area.
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