Autocross Weather

2015 SCCA Dixie Tour Weather - Saturday 06Z GFS Runs

3/7/2015

My friend and very awesome meteorologist, Robert Gamble with WXSouth.com had this to say this morning.

Before then, true south flow will occur starting next week, and only get stronger late next week into next weekend, with at least 2 strong waves of moisture pulling into the Southeast. Its still too early to say if west of the Apps is wetter, or east, or how much of Florida gets in on this...but one thing is certain, its going to get wet over a very wide region, somewhere between eastern half of Texas to the Carolinas, and quite possibly a good smattering between all this region. Eventually I'll be able to hone in on exactly where gets too much rain by late next week. A rough first guess is Louisiana, Mississippi, Alabama and Florida Panhandle..but the Southern Apps may join that group eventually.

First, lets look at something the European has been showing a few days. Notice just how deep the 5H height contours dive into Mexico and the Gulf in 5 to 8 days. As a synoptician, this sets off alarm bells. This is quite anomalously far to the south with 2 contours of deep onshore flow. Hopefully this doesn't translate into a 3 contour Gulf onshore flow at this particular angle---because as it stands now, the European keeps this flow long enough in place to do damage already. And if you squeeze one more contour into that narrow zone and hold it stationary, it would get into severe Flooding with time. I'll keep an eye on the 5H details like that for the Gulf states next week--because synoptically, that's already a harbinger of a heavy rain event, and getting very close to a pretty bad flooding event.

Notice the direct northerly flow off of the Gulf. The door is wide open.

Image courtesy WXSouth.com

Precipitable Water values Saturday 8 AM

So as you can start to gather... things are looking wetter and wetter. Keep in mind that the exact placement of the precipitation is still unknown, the maps just give you a general idea at this point. Here is the Extended Range Forecast Discussion from the Weather Prediction Center this morning.

EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1231 AM EST SAT MAR 07 2015 VALID 12Z TUE MAR 10 2015 - 12Z SAT MAR 14 2015 THE GLOBAL NUMERICAL GUIDANCE INDICATES THAT THE FLOW IS IN FLUX ACROSS CENTRAL NORTH AMERICA AT THE MEDIUM RANGE, WITH CHANGES FROM THE SHORT RANGE UNDONE BY THE TIME DAY 7 ROLLS AROUND. STUCK WITH THE ENSEMBLE MEANS FOR THIS VOLATILE REGIME, WHICH SHOW ENOUGH OF A RELAXING OF THE NORTHERN STREAM TO ALLOW WIDESPREAD PRECIPITATION TO BREAK OUT FROM THE GULF OF MEXICO TO THE OHIO VALLEY AND MID-ATLANTIC--MOSTLY IN THE FORM OF RAIN. THE WEST COAST IS WETTEST DAYS 4 AND 5, WITH THE TENDENCY TOWARD RIDGING ONCE AGAIN SHUTTING DOWN THE PRECIPITATION DAYS 6 AND 7. MUCH OF THE NATION WILL BE MILD UNTIL LATE IN THE PERIOD WHEN A SPRAWLING SURFACE HIGH BUILDS ACROSS SOUTHEASTERN CANADA AND FEEDS COLD AIR BACK INTO THE BORDER STATES.

And an excerpt from the Tallahassee NWS forecast office in their forecast discussion:

.Long Term [Monday Night Through Saturday]... The overall upper pattern will remain rather stagnant through much of the extended with the trough over Texas/Mexico and ridge extending from the Bahamas into the eastern Gulf of Mexico. This will keep the weather generally mild and somewhat unsettled rain- wise. The forecast area will be situated right along the boundary between the ridge to the east and the deep moisture being pulled from deep in the tropics to the west. Expect to see primary corridor of moisture and lift remain to the west and north through Wednesday, with PoPs ranging from isolated in the southeast to scattered/likely in the west. The upper trough will likely begin to slide eastward by late in the week, increasing rain chances across all of the area on Thursday and Friday.