Somewhat subtle to nearly astounding changes have occurred overnight along the immediate east coast that are quite surprising, and it appears that additional surprises are in store.
First off, the KSC sounding indicated precipitable water to be nearly 2.1" today, a far cry from the 1.67" of yesterday (much more moist), and this moisture isn't limited to any one or two specific layers but rather the entire column. This means, no real capping dry air aloft. The problem for the near future (for those who actually want rain) is that a narrow band of drier air is looming just off the coast. The location and movement of that sliver has two potential impacts. (1) It will sit there and prevent showers from forming off shore and moving onto the coast, (2) it might shift over the area and prevent showers from either forming on the immediate coast or kill anything that moves in from the east. Hence, even though we are more saturated today we still may not see any rain, at least not until late this afternoon.
The dry slot is on the leading edge of an extra moist pocket of air (remnants of "Fred")...and this poses yet another complexity to the forecast. Most models are depicting this area to move into the Carolinas/Northeast Georgia, yet current water vapor loop and wind field analysis shows that this trend is not at all to what's actually occurring. In fact, it looks like the remnants have split..with the high level energy indeed moving into the Carolinas, while the lower level 'stuff' is moving dead west toward East Central Florida. I believe the dry slot off shore is subsidence ahead of this forward motion.
What this all means? The dry slot will either move over or remain just off shore and gradually dissipate during the day. The first hint of moisture from "Fred" will move in during the course of the late afternoon, with the bigger slug to arrive mid-afternoon Wednesday. For the most part all of this will mean little more than a slightly increasing chance of coastal rain showers on the east coast..while the West Coast's pattern remains unphased. It does appear that the bulk of shower activity on the West Coast will be from the immediate Tampa Bay area to just south of Ft Myers with most of it clinging around the Bay and south right along the coast. Inland areas away from both sides it appears will only receive remnant shower debris as a sea-breeze collision in the true sense does not appear to be a threat. However, given ample heating and destabilization lake-breeze /sea-breeze interactions are still possible especially in Lake County and around Lake Okeechobee. It currently appears that the moisture, as defragmented as it is, will arrive in 'waves' at any given time, so there is no specific time frame when one can predict it is most likely to rain. This will be the case from late this afternoon into mid-day Thursday.
Moisture levels will return to their lower levels along the east coast after mid-day Thursday and remain as such until an approaching cold front struggles into the Deep South and eventually Florida. But that's a new story for a new day in this weather log's entry.