AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 PM CDT THU JUN 17 2010

.SYNOPSIS…
UNSEASONABLY STRONG 994 MB CYCLONE 2-3 STANDARD DEVIATIONS FROM NORMAL CENTERED IN ND WITH IMPRESSIVE COLD FRONT EXTENDING ALONG THE MN/DAKOTAS BORDER TO EXTREME NW KS. VERY UNSTABLE AIRMASS AHEAD OF THE FRONT WITH CURRENT TEMPS 90+ WITH DEWPOINTS 70+. BEHIND THE FRONT DEWPOINTS DROP OFF DRAMATICALLY INTO THE 20S WITH GRADIENT WEST WINDS GUSTING TO 50 KNOTS. CLUSTERS OF STORMS WERE LOCATED IN ND AND NORTHERN MN WITH OTHER STORMS JUST STARTING TO ERUPT ALONG THE COLD FRONT IN EXTREME WESTERN MN. HAD A FEW STORMS EARLIER TODAY IN THE WESTERN DVN CWA BUT HAVE SINCE DISSIPATED AS THEY OUTRAN THE BETTER MOIST AXIS AND FORCING FURTHER TO THE WEST. CURRENT TEMPS IN THE DVN CWA WERE IN THE 80S WITH DEWS IN THE 60S TO LOWER 70S.

.SHORT TERM…TONIGHT AND FRIDAY…
FULLY EXPECT A MATURE LINEAR MCS TO FORM REMAINDER OF THIS AFTERNOON FROM WESTERN MN TO WESTERN IA…AND THEN PROGRESS EAST. OPERATIONAL MODELS FAIRLY SIMILAR IN BRINGING THIS SQUALL LINE INTO OUR WESTERN CWA THIS EVENING WITH POTENTIAL FOR DAMAGING WINDS OF 60-70 MPH AND ISOLATED LARGE HAIL. MODERATE RISK REMAINS FOR SEVERAL COUNTIES IN THE CWA AND WILL MENTION SEVERE WORDING IN THE GRIDS/ZFP ONLY IN THE MODERATE RISK AREA. MCS SHOULD DIMINISH OVERNIGHT AS IT CONTINUES TO MOVE EAST OR SOUTHEAST. HAVE NOT ISSUED A FLASH FLOOD WATCH FOR THIS EVENT YET BUT LOCALLY VERY HEAVY RAIN MAY CAUSE FLASH FLOODING IN SOME SPOTS. WILL CONTINUE TO MONITOR THE PROGRESS OF THIS SITUATION AND A FLASH FLOOD WATCH CAN ALWAYS BE ISSUED THIS EVENING. THERMODYNAMICALLY SPEAKING THE GREATEST INSTABILITY IS TO OUR WEST AND THIS IS WHERE THE MOST INTENSE ACTIVITY SHOULD REMAIN. TIME WILL TELL. WILL FORECAST MIN TEMPS IN THE LOWER TO MID 70S SO THE MUGGIES ARE BACK WITH A VENGEANCE.

FRIDAY…POTENTIALLY A MORE WIDESPREAD AND MORE INTENSE SEVERE WEATHER EVENT UNFOLDING FOR FRIDAY LATE AFTERNOON INTO FRIDAY NIGHT. AS IMPULSE PASSES BY TO THE NORTH TO SUPPLY SOME DYNAMICS AND MID LEVEL WINDS INCREASE TO OVER 50 KNOTS MODERATE TO STRONG DEEP LAYER SHEAR EXPECTED. COLD FRONT WILL BE APPROACHING FROM THE WEST WITH THE AIRMASS AHEAD OF THE FRONT HAVING MLCAPES OF 2000-3000 J/KG. SURFACE DEWS SHOULD BE AT LEAST IN THE LOWER TO MID 70S WITH TEMPS AROUND 90. THIS RAISES THE POTENTIAL FOR A WIDESPREAD WIND DAMAGE OR DERECHO EVENT WITH AT LEAST 70-80 MPH WINDS. THESE SPEEDS ALONG WITH SATURATED SOILS COULD EASILY BLOW OVER MANY MORE TREES THAN USUAL IN THIS TYPE OF EXTREME EVENTS. EXPECTING A HIGH END EVENT WITH CURRENTLY SPC HAVING THE ENTIRE CWA IN SLIGHT RISK WITH UPGRADE TO MODERATE RISK POSSIBLE. WILL MENTION SEVERE WORDING FOR FRIDAY AFTERNOON IN OUR WESTERN CWA AS COLD FRONT APPROACHES FROM THE WEST. STAY TUNED TO LATER FORECASTS AND HAZARDOUS WEATHER OUTLOOKS CONCERNING THIS SCENARIO.

PRECIPITABLE WATERS WILL BE APPROACHING 2.00 INCHES SO CERTAINLY THE THREAT OF TORRENTIAL RAINS WITH RATES OF 2 INCHES PER HOUR RAISING THE RISK FOR FLASH FLOODING ON ALREADY SATURATED SOILS. ANY WIDESPREAD HEAVY RAINS WOULD ALSO GREATLY AGGRAVATE OR CAUSE NEW RIVER FLOODING.