SWODY1
SPC AC 170555
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT FRI SEP 17 2010
VALID 171200Z - 181200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM NRN KS INTO SRN AND ERN
NEB...CNTRL IA AND NWRN MO...
...SYNOPSIS...
A LARGE LOW AMPLITUDE UPPER LOW/TROUGH WILL MOVE EWD ACROSS CNTRL CA
AND ACROSS THE NRN PLAINS TODAY...FLATTENING THE UPPER RIDGE ACROSS
THE CNTRL PLAINS BY LATE IN THE DAY. MEANWHILE...AN UPPER SHORTWAVE
TROUGH AND SURFACE LOW WILL BE PRESENT NEAR THE NEW ENGLAND
COAST...BUT WILL DEPART DURING THE DAY WITH RELATIVELY COOL AIR
ALOFT IN A NWLY FLOW REGIME EXTENDING SWD INTO THE APPALACHIANS. AT
THE SURFACE...A COLD FRONT WILL SLOW ACROSS SRN NEB...WITH SLY
BRINGS BRINGING MID TO UPPER 60S F DEWPOINTS NWD AS LOW PRESSURE
DEVELOPS NEAR THE KS/CO BORDER.
...NRN KS/SRN NEB INTO IA AND NRN MO...
SURFACE WINDS WILL INCREASE OUT OF THE SOUTH TODAY AS LOW PRESSURE
DEEPENS OVER WRN KS/ERN CO. DEWPOINTS IN THE 65-70 F RANGE WILL
SPREAD NWD INTO KS AND SRN NEB WHERE A SURFACE FRONT WILL STALL THIS
AFTERNOON AS WINDS N OF THE FRONT VEER TO ELY. STRONG HEATING AND
PRESENCE OF RELATIVELY STEEP MID TO UPPER TROPOSPHERIC LAPSE RATES
WILL RESULT IN STRONG INSTABILITY WITH FORECAST SOUNDINGS INDICATING
MUCAPE IN EXCESS OF 3000 J/KG. STORMS ARE EXPECTED TO INITIATE FIRST
ACROSS NWRN KS/SWRN NEB WHERE LOW LEVEL LAPSE RATES WILL BE DRY
ADIABATIC. THESE STORMS MAY BE HIGH BASED INITIALLY...BUT WILL
LIKELY FORM INTO SUPERCELLS AS THEY SHIFT EWD ACROSS NRN KS/SRN NEB.
EFFECTIVE BULK SHEAR ON THE ORDER OF 40 KTS BY 00Z AS WELL AS LOW
LEVEL VEERING IMMEDIATELY NEAR THE SURFACE BOUNDARY WILL FAVOR
SUPERCELLS CAPABLE OF VERY LARGE HAIL...DAMAGING WINDS AND ISOLATED
TORNADOES. TRAINING SUPERCELLS...SOME BOWING AND PRODUCING DAMAGING
WIND...SHOULD PERSIST ALONG THE BOUNDARY THROUGH THE PERIOD AS A
SWLY LOW LEVEL JET ENHANCES LIFT AND MAINTAINS INFLOW. ACTIVITY
SHOULD EVENTUALLY MERGE INTO ONE OR MORE SMALL MCS'S WITH MAINLY A
DAMAGING WIND AND HEAVY RAIN THREAT INTO IA AND NWRN MO BY THE END
OF THE PERIOD.
...WRN NC/NWRN SC...
A WEAK THERMAL TROUGH ALOFT WILL EXTEND SWD ACROSS THE APPALACHIANS
WHICH WILL COMBINE WITH STRONG HEATING TO PRODUCE MARGINAL
INSTABILITY WITH STEEP LOW LEVEL LAPSE RATE PROFILES. ALTHOUGH
MOISTURE WILL BE LIMITED...AT LEAST ISOLATED CONVECTION IS LIKELY TO
FORM OVER THE HIGHER TERRAIN OF WRN NC INTO NWRN SC. NWLY FLOW ALOFT
ALONG WITH THE RELATIVELY DRY BOUNDARY LAYER PROFILES INDICATE A
THREAT OF A FEW STRONG TO POSSIBLY SEVERE WIND GUSTS BY LATE
AFTERNOON.
..JEWELL/GARNER.. 09/17/2010
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