Major Flooding Expected This Weekend Across Parts of Ohio& West Virginia.

A FLOOD WATCH has been issued for all of southern and parts of central Ohio through the first half of this weekend.  In the watch area flooding, that may be widespread and significant, is expected.  North of the watch area, at least minor issues are possible.  This flood threat is a culmination of a recent wet weather pattern that’s already produced some flooding and additional heavy rain falling this weekend on already saturated grounds and already high streams and rivers.

WHAT WE’VE ALREADY SEEN:

Observed rainfall between 7am on Thursday, February 15th and 7am Thursday, February 22nd

Essentially all of Ohio has seen over two inches of rain over the last week, with some portions of extreme southern and extreme eastern Ohio seeing over four inches.  Note that some additional rain fell this morning after the cutoff, so some areas have actually seen a little more than this map shows.  This rain has saturated the ground across all of Ohio and already caused its own flooding, with some river flooding across all portions of the state at some point over the last week.  Particularly hard hit have been parts of east-central, southeastern, and southern Ohio, where there have already been two separate widespread flooding episodes and where the Ohio River has already seen a crest in the “moderate flood stage” range at many river gauges.  Rivers in Northwest Ohio also are currently seeing flooding as the very heavy rain over northern Indiana gets into some rivers, such as.  Needless to say, we’ve already seen enough rain.

THE WEATHER PATTERN THIS WEEKEND:

Forecast total atmospheric moisture content (called Total Precipitable Water) compared to average

A prolonged southwesterly flow over the eastern United States will funnel unusually moist air north into the Ohio Valley and Great Lakes through the weekend.  This air is expected to have a moisture content that’s at times over 4 standard deviations above average over Ohio for this time of year, making it a very anomalous and close to record-setting event…and increasing the odds of more heavy rain.

Modelled upper-level winds Saturday night across the eastern US

In addition to all of the moisture moving into the region, we’ll be located beneath a favorable upper-level wind pattern for storminess and precipitation.  Being to the south/southwest of a strong region of jet stream winds, known as a “jet streak,” is known for being active and stormy, as that area relative to a jet streak sees upward motion.  This will promote numerous waves of low pressure and enhanced rain chances moving through the region between late Thursday night and Sunday morning.

Much of the state will see one to locally four inches of rain this weekend, with the highest amounts likely where any heavy rain/storms repeatedly track.  All of the state is vulnerable to heavy rain and flooding right now, with the areas worst off being parts of central and southern Ohio where the best shot at a few inches of rain is.  Much of the state can expect at least some minor flooding issues through this weekend, with significant issues possible in central and southern Ohio.  We will need to watch the northern edge of the heaviest rain closely, as any adjustment north could bring more significant flooding north of the current flood watch area.

Excessive rainfall outlook for Friday-Friday night from the Weather Prediction Center

Excessive rainfall outlook for Saturday-Saturday night from the Weather Prediction Center

There is currently a slight risk (risk level 2 of 4) for excessive rain and flash flooding across parts of central and southern Ohio for Friday and Friday night from the next round of rain, and a slight to moderate risk (risk levels 2 of 4 and 3 of 4) for central and southern Ohio for Saturday and Saturday night.  There is a marginal risk (risk level 1 of 4) for northern Ohio both time periods.  These outlooks are issued by the National Weather Service’s Weather Prediction Center.

These risks indicate the potential for rain heavy enough to cause flash flooding in a given area in each timeframe.  Flash flooding is when heavy rain causes rapid water rises, typically in urban areas and along smaller creeks and streams.  A moderate risk indicates a 20-50% chance of this occurring, which is substantial.  As discussed above, some flooding may occur from the round late tonight into Friday, but the more substantial rounds look to be Saturday through early Sunday.

Forecast river crests at gauges across the region from the Ohio River Forecast Center

In addition to the potential for urban and small stream flooding as the rain is ongoing, the repeated heavy rain over a large area will cause many main stem rivers to rise and potentially flood.  Most larger creeks and rivers are expected to approach or hit flood stage through the weekend in Ohio.  It’s worth noting the flooding on northwest Ohio rivers is mainly from rain that’s already fallen.

Of particular concern is the expectation of a major flood to move down the Ohio River later this weekend into early next week, with crests at moderate to major flood expected all along the Ohio River.  Some gauges may even approach record levels.  Other larger rivers in parts of east-central and southeastern Ohio will also likely flood.

You can monitor real-time river levels and forecasts here:

http://www.weather.gov/ohrfc/

In general, a lot more rain is coming, and this will cause new flooding across the state.  In parts of southern and central Ohio, this flooding may be widespread and significant.  Flash flooding in urban areas and on smaller creeks/streams as the rain is falling, river flooding on larger waterways, and flooding/standing water in any low-lying and/or poor draining areas will all be concerns this weekend.  If you live in a flood prone area and are ordered to evacuate, heed those orders.  Monitor any streams, creeks, and rivers near your location for rises through the weekend.  If you come across a closed or flooded road…many of which are likely…never drive through them.  Remember, turn around, don’t drown!  The good news is next week looks much quieter, giving us a chance to dry out.

More Updates this morning into the afternoon.