Monday will be our 12th day in a row with above normal temperatures in Gainesville, and on average the city is a full six degrees above what is typical for this time of year. What hasn’t been above normal – or even near normal – is the rainfall. Since the rainy season ended in early October, Gainesville has a rainfall deficit of more than four inches. Both of these trends will be slowed, or even halted, this week as the first significant front of the early winter season arrives in The Sunshine State on Tuesday.
THE BOTTOM LINE
Monday: AM fog, midday sun, then showers (some thunder) likely 4pm – 10pm
Tuesday: Partly sunny early, then rain likely by afternoon. Turning much cooler late.
Wednesday: Periods of rain, ending by late afternoon. Breezy and cooler.
The Set Up
As mentioned in our 10-day forecast a few days ago, the jet stream is shifting across much of the United States. This river of air that steers storms and separates air masses has been displaced unusually far to the north for much of the past month, allowing warm and dry weather to persist across much of the southern and southeastern parts of the country. Over the weekend, a strong storm began to carve out a trough (or dip) in the jet stream, which will force a cold front much farther south than its predecessors.
This front, likely arriving in Florida on Tuesday, will also have plenty of moisture moving ahead of it to work with, evidenced by all the low clouds and fog we have seen recently. It’s this moisture, being lifted by the approaching front, that will likely produce the first widespread rainfall event this state has seen since early October. An upper-level disturbance moving along the front will also aid in the beneficial rain that is forecast to fall, especially across central and northern parts of the state.
Timing of the Rain
Showers are possible as early as Monday evening with a disturbance moving out of the eastern Gulf. The majority of the rain associated with the passing front, however, will likely hold off until late Tuesday or early Wednesday. Monday evening’s rain is most-likely in Levy, Citrus, Marin, and Putnam counties, or along and southeast of the US HWY 24 corridor between 6 and 9pm. The rain that arrives later on Tuesday will be a bit more widespread, and possibly accompanied by some thunderstorms with heavier downpours. Wednesday’s showers, likely the final episode of precipitation with this system, will be a bit more scattered in nature and not as heavy.
Rainfall amounts from this 2-day system won’t make up for the deficit we have acquired over the past three months, but it will likely represent the most significant rainfall event we have seen since October 3rd, when more than two-tenths (0.2) of an inch fell in an afternoon thunderstorm. Most locations of North-Central Florida are forecast to receive between 0.25 and 0.5″ of water, but locally higher amounts will be possible where any stronger thunderstorms can form. In fact, some model guidance suggests that more than an inch of rain could fall near the I-4 corridor in central Florida, where the front will linger longer on Wednesday.
The environment ahead of the approaching front will become slightly unstable, meaning that a few strong thunderstorms are possible in portions of the state. This will most-likely occur where maximum heating can be achieved prior to the arrival of the front. Much of North-Central Florida will see the cooler air sneak in before maximum heating can occur on Tuesday, thereby preventing strong storms from forming. However, distant rumbles of thunder could still accompany some of the heavier downpours, even behind the front and in the cooler air Tuesday night.
Cooler, drier air will move into the state in the wake of the front Wednesday. Temperatures will fall back to or slightly below the seasonal norms, largely in the 60s for daytime highs and 40s for overnight lows. Another storm system moving across the southern United States could bring back the chance for rain by late in the coming weekend (15-16th), with another decent shot of cooler air behind it. A long-lasting and significant blast of cold air is not forecast to make this far south in the next 10 days, largely due to the jet stream’s alignment staying slightly to our north.
WRUF Weather will have frequent updates on the unfolding weather situation this week, and we invite you to follow us on Twitter @GatorWeather for any urgent updates.