Aug. 9-17 Heavy Rain/Flood Threat

[snowlover2]

From now until Friday there's the possibility slow moving torrential rain makers causing flash flooding especially IN/OH which is why the early start date. By the weekend it's looking like a more widespread heavy rain event across the southern half of IL and especially IN/OH. WPC QPF says it all.

[snowlover2]

Latest WPC QPF and ILN AFD.

 

Quote

Area Forecast Discussion
National Weather Service Wilmington OH
336 PM EDT WED AUG 10 2016

.SYNOPSIS...
A warm and muggy airmass will remain in place across the region
into this weekend. The combination of this and a slowly
approaching cold front will result in a continued chance of showers
and thunderstorms into early next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Much of our area is on the periphery of the more widespread
thunderstorm activity this afternoon. We are generally seeing just
some isolated coverage with the exception of portions of East
Central Indiana. Some of this activity will likely work northeast
across northwest portions of our fa through early evening.
Meanwhile, The best instability at the moment is across southern
portions of our fa where they have been less worked over so far
today. The HRRR is indicating some additional development in those
areas through mid to late afternoon so will allow for some
slightly higher pops down there into early evening. With the pcpn
diurnally enhanced, will gradually taper pops back to 20 percent
overnight. With light flow and PWs in excess of 2 inches, locally
heavy rainfall/flooding will remain possible with the stronger
storms.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Expect more of the same on Thursday as we will remain on the
northwest edge of the ridging across the southeastern US. In the
continued warm and muggy airmass, expect highs again up into the
upper 80s to around 90 degrees. There does not appear to be much
in the way of forcing through the day so think this will help keep
the thunderstorm coverage more isolated to scattered and
diurnally driven. Will continue with chance pops, mainly for the
afternoon into early evening hours. PWs will again be in the 2 to
2.25 inch range and with the light flow regime, the threat for
torrential downpours and localized flash flooding will persist.

The combination of the high dewpoints and temperatures up close
to 90 degrees will once again push heat indices into the upper
90s to around 100 degrees Thursday afternoon. Will go ahead and
add a mention of this into the HWO product as well as
continuing to highlight the heavy rain/flash flooding threat.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...

-- Changed Discussion --

The biggest concern during this time period will continue to be anomalous/extreme ribbon of moisture draped across the area...being perturbed by weak disturbances both rotating around the strong Bermuda high...and on the southern fringe of the westerlies. Ensemble and deterministic runs continue to paint the Friday-Sunday time period with extreme PWAT for mid August - putting out 2.10" to 2.35 consistently within and amongst the runs. The places standardized anomalies from +2 to +3 sigma...and climatology PWAT percentiles > 99%. Considering there are only a handful of KILN RAOB measured PWATS > 2.25" in the period of record during August...the consistent forecast of these values for several days in a row confirms this will be a continued long-duration environment that supports tremendous rainfall rates given expected warm cloud depths > 5km...a weak southwesterly low/mid level flow /which tends to promote regeneration/backbuilding/....a being on the favorable southern fringe of mid/upper level jetlets. The potential is there Saturday/Sunday for a stronger shortwave crossing the Great Lakes to induce a more significant flash flood event (or events) as a weak convergence axis remains draped across the area and is acted on by several weak waves following it. There`s a signal for widespread storms Sat aftn/eve to backbuild into a secondary 925-850mb moisture transport maximum developing to the southwest attendant to the approaching height falls. Should this occur...the concern for flash flooding increases as duration of heavy rain potential undoubtedly lengthens. This will need to be watched closely...and there is concern even into early next week that round after round of storms with torrential rates will impact the ILN forecast area. It`s a moderate to strong signal of a near favorable setup for higher-end flash flood threat should the timing of waves and layout of the lower level boundaries become favorably juxtaposed. Backtracking a bit...Friday will likely to continue to feature a few showers and storms...but loosely focused like in recent days. It`s not until Saturday-Sunday-Monday where the potential really increases. Heat indices Friday could get close to Advisory criteria like today. Days will continue to be very muggy with more clouds than sun due to repeated shower/storm chances. Thus...raised overnight lows...and reduced afternoon highs.

-- End Changed Discussion --

 

[Chitown Storm]

Complex to the north of the TC slowly sagging south. The metro might be in line for training storms overnight. Latest HRRR run shows this, especially north metro. Might be a long night for a lot of folks that don't need a drop of rain  

 

Edit: pic of the mothership rolling in. Reports of 2-4" falling in 90 min just west of Minneapolis. Here we go...

[snowlover2]

[IWXwx]

Mike Ryan at IND has  a nice writeup concerning the upcoming heavy rain potential for Central/Southern IN:

https://nwschat.weather.gov/p.php?pid=201608110822-KIND-FXUS63-AFDIND

[A-L-E-K]

looks like a pretty good risk of getting skipped over (to the north this evening and just south tomorrow afternoon)

 

 

[Chitown Storm]

4.2" of rain in the gauge from 9pm last night to this morning. Expecting another heavy round late this afternoon.  Flood Watch extended until this evening. So water logged. 

[hawkeye_wx]

The weakening mcs, which dropped only 0.11" on my yard, has pushed the outflow down to near the Missouri border.  That could certainly affect the later action.  The HRRR has shifted the evening/overnight action to central/southern Iowa, with nothing in Minnesota.

[hawkeye_wx]

The influence of the morning mcs cold pool is quickly waning.  Central and southern Iowa has surged back well into the 80s with dews well into the 70s.  Latest model runs are blowing up convection from east-central back into nw Iowa later, with possible training somewhere in there.  DVN is mentioning 3-5 inches with isolated 7 inches possible in this area tonight.

[A-L-E-K]

Yeah obvious heavy rain setup to my west and southwest

[snowlover2]

[Chicago Storm]

Out camping at White Pines Forest State Park (Few miles east of Polo, IL) from yesterday through Sunday.

DVN with a FFW up just west of here, with LOT holding off for now.

Round 1 this morning provided some nearby storms and light rains, but this evening and overnight will prove to be interesting with a couple inches of rain and constant storms possible.

[cyclone77]

3 hours ago, hawkeye_wx said:

The influence of the morning mcs cold pool is quickly waning.  Central and southern Iowa has surged back well into the 80s with dews well into the 70s.  Latest model runs are blowing up convection from east-central back into nw Iowa later, with possible training somewhere in there.  DVN is mentioning 3-5 inches with isolated 7 inches possible in this area tonight.

Looks like a new Great Lake is going to form later tonight somewhere not far from you guys.

EDIT:  4km NAM forecasting 15" of rain east of Waterloo tonight lolz.

[cyclone77]

52 minutes ago, Chicago Storm said:

Out camping at White Pines Forest State Park (Few miles east of Polo, IL) from yesterday through Sunday.

DVN with a FFW up just west of here, with LOT holding off for now.

Round 1 this morning provided some nearby storms and light rains, but this evening and overnight will prove to be interesting with a couple inches of rain and constant storms possible.

You're only a county northeast of us lol.  Yeah I've been there before.  Pretty sweet place.  Shot this pic there in the dead of winter a few winters ago.  

 

[hawkeye_wx]

Just as the afternoon HRRR runs predicted, an east-west line of convection has trained through Cedar Rapids, dropping 3-4+ inches across the metro area.  My gauge has about 3.30".  It has fallen over a few hours, though, so there is no big flooding problem.  It appears we're done with the heavy stuff.  The rest of the night we'll be under the light to moderate rain shield.

[cyclone77]

29 minutes ago, hawkeye_wx said:

Just as the afternoon HRRR runs predicted, an east-west line of convection has trained through Cedar Rapids, dropping 3-4+ inches across the metro area.  My gauge has about 3.30".  It has fallen over a few hours, though, so there is no big flooding problem.  It appears we're done with the heavy stuff.  The rest of the night we'll be under the light to moderate rain shield.

You've dominated the entire sub in heavy rainfall this summer.  We've done very well here, but you've blown even us out of the water, no pun intended lol.

Up to 0.81" here.  Getting bursts of heavy rain, but the torrential stuff never got into here.  

[Chinook]

I woke up in the middle of the night here. I grabbed these storm total images from the IA radars (both include about 25 hours worth of time)

 

 

 

[hawkeye_wx]

I have 3.62" in my gauge this morning.  5-6 inches fell in a narrow band just south of the city where the the line stopped sagging southward and trained for a few hours.  Including yesterday morning's rain, I received 3.73".

[cyclone77]

Another 1.77" fell since midnight, and still raining.  Combined with yesterday's 0.94" makes for 2.71" total. 

[hlcater]

I finished with 2.87 but there's LSRs along the Linn County/Johnson County line area reporting that 5.5 to locally over 6" of rain has fallen. They certainly took the brunt of the training storms, but even farther north, was still a decent event.

[buckeye]

ILN:
Several factors point to the potential for very heavy rain and
flash flooding this weekend. A very moist environment in place
with PW/s at or above 2 inches thru the weekend. Numerical models
increase pw/s to between 2.4 and 2.5 inches Saturday evening.
These values approach ILN/s record PW to 2.54 inches which
occurred 7/29 00z in 1966.

As a weenie layman, I have no idea what a PW is, but anytime we have the chance to beat a 50 year old record....

I'm in!

[Hoosier]

Line about to hit here.

[hawkeye_wx]

The big winner last night was a Cocorahs spotter near Swisher, just south of the Cedar Rapids airport, who reported 7.04".  DVN suggested widespread 3-5" with isolated 7... can't do much better than that.

[Jonger]

2 hours ago, buckeye said:

ILN:
Several factors point to the potential for very heavy rain and
flash flooding this weekend. A very moist environment in place
with PW/s at or above 2 inches thru the weekend. Numerical models
increase pw/s to between 2.4 and 2.5 inches Saturday evening.
These values approach ILN/s record PW to 2.54 inches which
occurred 7/29 00z in 1966.

As a weenie layman, I have no idea what a PW is, but anytime we have the chance to beat a 50 year old record....

I'm in!

The term has probably been around a long time, but it has recently been used more frequently.

[knitwx]

I can't believe I'm the one posting this; There is a tornado warning Southwest of Holland Mi.

[HillsdaleMIWeather]

GRR just issued a Flood Watch for there southern CWA.

[snowlover2]

Latest WPC 7 day QPF. Break out the boats.

[Stebo]

2.50" here would be a godsend.

[HillsdaleMIWeather]

Just drove into torrential rain in Jackson

[CoalCityWxMan]

Could be a decent flash flood threat setting up in central IL north into NE IL along the front