Saturday, August 15, 2009

FCST 8-16 ~ Southern IA / Northern MO

EDIT: 1636 cdt Weak vorticity minima in central Kansas and main short wave in SE CO is forecasted to move to the east northeast this afternoon into this evening....the cold front is currently in the northwest corner of MO and extends southwestward into Kansas.....the cold front shows up nicely on the KTWX and KICT BR 0.5 deg radar scans....my current area of of interest would be in the area near the "kink" in the cold front and just northeast of the vorticity minima.....for what it is worth and it is August and I am typing this is enough to interest me on a Sunday afternoon ~~~ CS

EDIT: 1130 cdt Subsidence in the wake of the early morning convection has stabilized the atmosphere....the current vis satellite image does not bode well for the sun breaking out and causing enough destabilization in the target area by the peak heating of the afternoon....therefore, the target area described yesterday is a wash....I do expect severe weather in central and southeast Kansas this afternoon where the clouds have cleared...large hail and damaging winds will be the primary threat.....heavy rains will also accompany the slow moving cold front and associated convection ~~~ CS



Target Area: Southern IA / Northern MO (Tarkio, MO to Red Oak, IA) Storm mode=multi-cell with possibility of embedded supercells) Primary threat large hail, damaging winds and heavy rain.

Forecast Discussion: Surface low over southern Canada with a slow moving cold front extending into the upper MS Valley is expected to reach the target area by late afternoon through the early evening hours......short wave visible over north central Kansas at 0Z.....diurnal heating ahead of the cold front should be enough to moderately destabilize the atmosphere for a localized severe weather event early on before the cold front overtakes early convection and a linear MCS evolves into the evening and overnight hours with an attendant damaging wind threat...the potential exists for very heavy rainfall into Monday across the target area (with PWV approaching 1.98" per KSTJ sounding and QPF forecasted in the 1 to 1.5" range)....southwesterly flow ahead of the cold front should allow Dp's to reach the low to mid 70's (some model soundings indicate a bullseye of 75 Dp's in NW MO at 0Z) and surface temps to be in the mid to upper 80's...surface winds of 10 kts and are slightly backed at 0Z, 35 to 40 kt bulk shear is also forecast.....CAPE values forecasted to be in the 1500 to 2500 j/kg (with 1600+ CAPE on the KSTJ sounding at 0Z/17) in the target area....DCAPE forecasted near 1300 j/kg...CINH forecasted to be in the -80 j/kg range at 0Z indicative of a fairly strong cap, but I think afternoon heating and forcing associated with the approaching cold front/short wave will erode the cap by later afternoon / early evening (700 mb temps are in the 10 to 12 C range) 0Z/17 KSTJ forecasted sounding values: EHI is 2.2, SRH is 222 0-3km and 203 0-2 km, SWEAT is 380ish, BRN is only 13......more later if my thoughts change ~~~ CS

Chase Summary:

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