Sunday Evening Forecast Discussion – 8 p.m.

An unsettled weather pattern for much of this week will be the main story for the forecast as several troughs as well as a cold front are poised to move through West Alabama. Rain chances are expected each day until Friday when the cold front should clear the area. Much drier and cooler air could be possible by the weekend, but confidence in the forecast lowers
after the frontal passage as long range model solutions differ.

Looking at the current setup, an upper level trough to our west continues to produce scattered to numerous showers and storms across much of the ArkLaMiss. Southerly flow at the surface has also increased moisture values to our west with widespread upper 60s to lower 70s dewpoints observed. Meanwhile, the wedge that has been present over the eastern portion of the state is beginning to weaken, based on observations over the past several hours, and this trend will continue over the next 12 hours as winds shift from the east and northeast around to the south and southeast. As the upper level trough approaches overnight tonight showers and isolated thunderstorms will increase in coverage across the western counties. Based on current satellite and radar trends we went ahead and raised
the rain chances to likely for the west. With the passage of the trough tomorrow, widespread showers and storms will exist across the western portion of the state with more scattered
coverage farther east. Model guidance has been fairly consistent with this feature.

The challenge in the forecast over the past few days has been the possible clearing after the first upper trough passes tomorrow. With the 12z ECMWF coming in, models have begun to gain a bit more consistency in the idea of not bringing in drier air on Tuesday and stalling the southeastward movement of the upper trough to our north and west. With moisture and instabilities continuing to be present, the GFS and ECMWF are continuing to advertise shower and thunderstorm development on Tuesday and Wednesday morning. However…the NAM and SREF continue to indicate drier air possibly being able to move in briefly from the northwest, so we went with higher end rain chances Tuesday and Wednesday morning due to this fact.

The next upper level disturbance looks to trigger widespread shower and thunderstorm development on Wednesday afternoon and evening across much of the southeast, as well as on Thursday ahead of the actual surface front. The GFS and ECMWF are fairly consistent with
the passage of the front on Friday, but then diverge towards the weekend with the ECMWF continuing to push in cool dry air from the northwest and the GFS splitting off a piece of energy in the form of a cut-off upper level low pressure area. Looking at the GFS ensembles, some of the members are generating the low to our north over the Ohio Valley while others are developing the low just to our west over northern Mississippi. It will be interesting to see which
solution the models decide to agree upon over the coming days.

Daniel Sparkman
dsparkman@wvuatv.com
WVUA Weather

Advertisements