Currently, we are situated in the southerly, return flow of an eastward tracking surface high pressure system. There is also a center of surface low pressure in the Gulf of Mexico due south of Louisiana pumping moist, Gulf air straight north into our area. This is creating moderate values of moisture for the lower Mississippi and lower Ohio River valleys. A significant short wave situated in the lower Mississippi River valley is aiding in the moisture advection and providing lift, giving us the current showers. Periods of rain today are more widespread and prolonged, with less severe implications. To our west exists a cold front extending from Michigan’s Upper Peninsula with a southwest orientation across Iowa and into the Texas panhandle, with the center of low pressure in the northern extent of Quebec.
Models are depicting the upper level support for the front to increase as the 250mb trough over the upper Midwest is deepening positively with a jet max on the down stream side over the Great Lakes. This, coupled with increasing vorticity and vertical velocity values extending at the surface frontal vicinity will help to provide substantial support for the front. Moisture advection from the Gulf is shown to continue before the expected frontal passage shown by both the NAM and GFS models as early Tuesday morning around 7 AM. Moderate to heavy rain and strong winds should be presumed as the main threat for the frontal passage. Periods of rain related to the front should be relatively brief, but intense. Models are showing a majority of the precipitation to be experienced to our east in eastern Kentucky and central Tennessee along the Cumberland Plateau with high probabilities of 3-hour accumulations around a quarter of an inch for the period of the next day. The HPC’s forecast for precipitation accumulations agree with the models showing over 4 inches for the same geographic area through tomorrow morning. I think this is a little exaggerated depending on the speed of the cold front and will keep precipitation amounts lower for our area. We are also along the projected precipitation gradient, so precipitation amounts for our area look to be one inch to an inch and a half in total. A flood watch has been issued for areas to our east because of the duo of soaking rains today with the frontal passage tomorrow morning. Behind the front, dry, cool air will look to bring a hint of fall as a surface high pressure situates over the area. A light jacket will be advisable.
Days at a glance:
Today: High 74 Low 65
Tomorrow: High 70 Low 44
Wednesday: High 67 Low 40