OVER ROTATION FELT BY THE FLT CREW OF A B737-300 AFTER LIFTOFF WITH PF CITING A PROB DURING A WINDSHEAR NIGHT OP DEP PROC AT ORD; IL.

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ON PREFLT; DISCUSSED WINDSHEAR PRECAUTIONS USE OF MAX PWR. DISCUSSED WITH DEICE LEAD TECHNICIAN NOT TO DEICE. ACFT CLEAN; NO SNOW STICKING; WINDS BLOWING HARD. WX RADAR INOP; NO PWS INSTALLED. ON TAXI OUT; WX WORSENING; VISIBILITY DOWN TO 1/2 MI; WINDS 240 DEGS AT 24 KTS GUSTING TO 39 KTS. TAXI TO RWY 22L. DURING WING CHK; HAD HARD TIME GETTING A CLR VIEW OF ENTIRE WING (DARK; BLOWING SNOW). WING APPEARED CLR OF ANY ACCUMULATION. USED B737 AHEAD TO CONFIRM OUR OPINION. TKOF ROLL NORMAL TILL 110 KTS. ANNOUNCED AIRSPD HANG-UP. AIRSPD JUMPED AHEAD. DELAYED ROTATION FOR WINDSHEAR. PF ROTATED; NORMAL LIFTOFF WITH L DRIFT. NORMAL POSITIVE RATE OF CLB; GEAR UP. I (PNF) NOTICED OVER ROTATION TO 2-3 DEGS ABOVE FLT DIRECTOR GUIDANCE. FELT PF WAS CORRECTING; THEN HEARD 'I HAVE A PROB.' THINKING IT WAS A PITCH CTL PROB; I PUSHED FORWARD ON THE STICK WITH THE CAPT TO LOWER THE NOSE 5 DEGS. SLIGHT AIRFRAME BUFFET AS NOSE WAS PUSHED OVER. CHKED PERFORMANCE INSTS. GREATER THAN V2+20 KTS; 1600 FPM CLB; ALT CLBING. CONTINUED NORMAL CLBOUT. ON REVIEW; IT APPEARED WE MAY HAVE HAD WINDSHEAR EVENT. HOWEVER; NO CAUTIONS OR WARNINGS. SUPPLEMENTAL INFO FROM ACN 573825: ON TAXI OUT; THE SNOW INCREASED TO NEAR BLIZZARD CONDITIONS. VISIBILITY WAS DOWN TO 1800-2000 RVR. AFTER LIFTOFF; I (PF); CALLED GEAR UP; BUT WAS STRUGGLING WITH A PERCEIVED ROLL PROB FROM LIFTOFF. I THOUGHT MAYBE I HAD AN ENG PROB. IT WENT AWAY AS I CLBED UP; BUT I PROBABLY LOST THE PITCH WHEN LOOKING TO THE ENG GAUGES. AS FAR AS WE CAN REMEMBER; THE WINGS WERE LEVEL FOR ALL THIS. WE WERE MAX PWR FOR TKOF.