This page has breaking 12Z model discussion as it comes in. Through day 5 discussion updates Monday-Friday by 12:15p Eastern, days 6-10 discussion and tropical update by 1:00p.
HEADLINE: MID-DAY GFS BRINGS TRULY INSANE RAINFALL TOTALS TO COASTAL TEXAS…
United States through Day 5: Through 120 hours, the 12z GFS is a little drier in northern Iowa and Nebraska and a bit wetter in the Ohio Valley with a front that will move across the corn belt from Saturday into Monday. Overall totals of around 0.5″ with 1″ accumulations common in Minnesota and Wisconsin continues to be our forecast. Otherwise, Harvey stalls over Texas on days 3-5, moving even more slowly on this run that the last several, with extreme flood risk in coastal Texas.
United States, Days 6-10: Through Day 10, the 12z GFS is similarly dry and mild across the corn belt for the most part. The major change is that this run is much slower to move Harvey away from the Texas coast, leading to truly absurd rainfall totals on the order of 2-3 feet between San Antonio and Houston. While this run likely stalls Harvey for too long, even rain totals a third of this model run will cause extreme flooding across already saturated eastern Texas. Harvey doesn’t move north until days 9-10, at which time the eastern corn belt receives some residual moisture; my thoughts are that the system will eject east a bit earlier and this rain will not get quite as far north, but uncertainty remains high with the eventual motion of this storm.
Tropical: Tropical Depression Harvey has reformed in the southern Gulf of Mexico. As indicated above, this system is a hurricane threat to the Texas coast, but foremost an extreme flood risk to southeast Texas and Louisiana. A full forecast video discussion will be out later today with the latest on Harvey as well as Invest 92L, which also may develop in 3-5 days east of Florida.