Update - Saturday 11am:
NRL has started Invest 94L on the system so an update seems appropriate. System still slowly organizing and at 28/12Z was centered near 20.5N 87.2W and moving northwest at 10mph across the northeast tip of the Yucatan peninsula. Pressure estimated at 1008mb. Development will still be slow since the large center will be over land today. Expect movement to the north northwest and eventually north. Tropical models intensify the system but they have quite a longitude spread at 120 hours - from 99W to 76W. With the northwest jog, the system will bypass the mid-level northerly shear to its east (the intensity of the shear has decreased in the forecasts). If you believe the report, Cozumel had 23.32 inches of rain between 06Z and 12Z this morning. Cancun reported 4 inches. Here is the link to the Cozumel weather report:

http://weather.noaa.gov/weather/current/MMCZ.html

and for Cancun:

http://weather.noaa.gov/weather/current/MMUN.html

Cheers,
ED

Original Post Friday Evening:
Weak low pressure area near 20N 86.5W southeast of Cozumel Island will be slow to develop, but a Tropical Depression is possible within the next 24 to 36 hours. System is currently stationary - not much in the way of steering currents - however weak southerly flow is anticipated over the area by Saturday morning. A slow drift to the north over the next few days seems likely. One inhibiting factor is that mid-level northerly shear is expected to increase between mid Saturday and mid Sunday in the Yucatan Channel and northward. Just to the west of the channel, the shear will be just about nil. If the system moves due north its development is questionable, but if it drifts to the north northwest it will move into a more favorable environment for development. Earlier visible satellite hinted at the development of embryonic low-level banding - not strong but evident in the satellite imagery. Steering currents are expected to remain weak out of the south in the east central Gulf over the weekend, becoming south southwesterly further north toward the northern Gulf coast south of the Florida panhandle. Nothing threatening but certainly an area of interest.
Cheers,
ED