As you can see by the dark green shading to your left, that the whole area is under a flash flood watch. This means that conditions are possible that flooding may occur with the heavy rain that is coming.
The set up is about as lined up as you can to get some flooding:
1) Slow moving N-S cold front. This means our mountain ridges run perpendicular to flow of precipitation. This enhances lift and rainfall intensity.
2) Front parallel to winds aloft (meaning at all levels of atmosphere the winds are blowing north. This enhances lift and rainfall intensity.
3) Tropical moisture connection.
The above simply means that Friday will be a washout. The rain will come down hard at times. Watch out for ponding of water on roads, localized flooding. Will the Swatara flood? If we get 3" or more of rain then yes it will. Right now 2-3" seems likely. The rain will start tonight and be out of the area by late Friday afternoon (maybe sooner as it looks to be starting a little sooner than thought 12 hours ago.)
Be careful. Looks like we will have a decent weekend. Lower humidity and much cooler temps with highs in the 60s and lows near 40 to upper 30s. Expect partly cloudy skies both days.
Pastor Terry. He received his bachelors degree in Meteorology from the State University of New York at Oneonta, in 1994. The education continued as a hobby by reading the blogs of some of the best forecasters in the business. Although forceasting the weather is an imperfect science, it is a pleasure to follow what the Creator has made.