The American Heart Association guidelines consider 120/80 to be "normal" blood pressure. Prehypertension is 120-139/80-89, and hypertension is 140 or higher/90 or higher.
255/190 is definitely an emergency and a situation where you need to contact your doctor or go to the emergency room immediately.
Please see your doctor and discuss this with him or her. Plans need to be made to address this so you don't have to go to the doctor or emergency room every time you have a Migraine. Please DO see your doctor about this. Blood pressure in that range can be dangerous.
Please keep me posted?
That is absolutely too high and you should head for the ER with a BP that high. Any BP of over 200 systolic increases your risk for a stroke and/or a heart attack. Longterm a BP ov 140/90 or higher puts you at risk a number of cardiac or cerebral issues.