Sunday Evening Forecast Discussion – 8:30 p.m.

We have a challenging forecast ahead of us as a complex setup of the low pressure over Florida moving northwestward increasing cloud cover and rain chances, as well as a cold front and trough poised to move through the Southeast by the end of the workweek.

First, the broad area of low pressure across southern Florida will continue its northwest jog over the next few days. Moisture levels will increase as precipitable water values are expected to rise over 1.5 inches by Monday afternoon. As the low pressure passes just off to our east, we will remain on the stable west side and plain old rain will be the only impacts. The forecast challenge will be how far west the rainfall and cloud cover will be able to spread. Any adjustment of the track of the low pressure will determine who gets rain and clouds all day and who sees more sunshine and warmer temperatures. A majority of the models are now indicating more cloud cover further westward from previous runs. For now, have gone with upper 70s for highs Monday. The bottom line will be that there will be a significant temperature gradient across the state. Rainfall amounts are expected to be light with this system with under one half inch of rain expected through Tuesday, but a few amounts could be a bit higher than that across the far east and southeastern counties with the stronger impulses that come in with the easterly flow. Winds will remain breezy through the day on Monday as well…with 10 knots sustained and gusts up to 20 knots across the south and east.

A brief break between systems looks to be possible on Wednesday as the low pressure quickly moves off to the northeast in response from the next trough developing over the central US. Looking at the main dynamics, both the GFS and ECMWF keep the strong jet streak to our north over the Ohio Valley on Thursday and Friday. The GFS is a little more progressive with the cold front moving through on Thursday afternoon, while the ECMWF is a little slower. Another difference is that the GFS does not allow any return of moisture from the gulf ahead of the cold front with a westerly flow, and the ECMWF allows a short time frame of moisture return from the south. Accordingly, the ECMWF is producing more rain and thunderstorm development along the front than the GFS, which keeps most development off to our north. Regardless of development or not, with the main uplift to our north strong or severe storms look unlikely at this time. After the passage of the front, cooler and drier air will move in from the northwest. Pleasant conditions with highs in the 70s and lows in the 40s could be possible by the weekend.

Daniel Sparkman
WVUA Weather