Valid 281200Z – 291200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
The risk of severe storms appears negligible today through tonight.
Generally stable conditions prevail across much of the U.S. and
little significant change appears likely during this period.
Within the main branch of westerlies emanating from the northern
mid-latitude Pacific, models indicate that positively tilted
large-scale troughing will remain prominent east of the Mississippi
Valley. However, upstream large-scale ridging is forecast to
gradually shift eastward across the northern Rockies and
northern/central Plains, as broad troughing develops across the
northeastern Pacific into the Pacific Northwest by 12Z Saturday.
Farther south, within a branch of westerlies emanating from the
southern mid-latitude eastern Pacific, a portion of the increasingly
sheared remnants of a mid-level low is forecast to continue
spreading inland across parts of the Southwest.
Strongest mid-level confluence into the eastern troughing appears
likely to gradually shift east of the Plains through the Mississippi
Valley by late Friday night. This will be accompanied by a building
surface ridge axis, to the north of a cold surface high centered
over the northwestern Gulf of Mexico. The presence of this surface
high and ridge will continue to inhibit inland low-level moisture
return, though boundary layer modification over the northwestern
Gulf of Mexico may gradually commmence.
With substantive low-level moisture return from the lower latitude
eastern Pacific also appearing unlikely, potential for appreciable
destabilization appears low. However, cold air aloft associated
with at least a couple of perturbations embedded within the
larger-scale flow may contribute to at least some risk for weak
…Ozark Plateau vicinity…
Cold mid-level air (-30 to -32C at 500 mb) and forcing for ascent
associated with a digging short wave impulse may contribute to weak
boundary-layer destabilization by late this afternoon. This is
expected to become focused ahead of a reinforcing cold front, along
an axis of stronger surface heating across southwest Missouri into
the Missouri Bootheel vicinity, where thermodynamic profiles may
become supportive of low-topped convection capable of producing
lightning. Activity will tend to spread southeastward before
diminishing after sunset.
Weak destabilization beneath the mid-level cold core (-34 to -36C at
500 mb) of a vigorous inland advancing short wave trough may become
sufficient for a few weak low-topped thunderstorms, mainly near
Washington/northern Oregon coastal areas by 29/03-06Z this evening.