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April 8-10 Severe threat


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4km NAM ignites convection as far west as Waterloo down to Ottumwa shortly after noon.  With large cape already in place (conditionally of course) we may have to play the Iowa side and take our chances with the bridges.  Storm motions tomorrow are gonna be a challenge, so dealing with bridges should really make it interesting lol.  

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4km NAM ignites convection as far west as Waterloo down to Ottumwa shortly after noon.  With large cape already in place (conditionally of course) we may have to play the Iowa side and take our chances with the bridges.  Storm motions tomorrow are gonna be a challenge, so dealing with bridges should really make it interesting lol.  

 

Do you mean Ottowa?

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As long as morning convection doesn't muddle things up too much, and short term models continue with ongoing trends I think we're going to target somewhere in the Iowa City/Waterloo/Ottumwa triangle.  May just play the triple point if it isn't too muddled up.  I think these sups will have the potential to tor within an hour after developing, so I want to be up close to where the boundary is by early afternoon.  Anything that fires ahead of the main band of storms over towards IL could go tornadic, and could be the best storms overall if enough cape can build after whatever happens in the morning.  

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The timing appears to be interesting on the 4k NAM, having them impact around 01z, or 8pm.. Not quite the rush-hour strike the 18z showed, now comes the waiting for the 12Z models and what those will bring. Someone in the Illinois area will definitely be looking at a bad day tomorrow. Oh, I will also have to sneak in weather monitoring both in and inbetween classes throughout the day. I wish everybody a delightful evening and safe chasing tomorrow! 

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Update from LOT about a half hour ago:

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
955 PM CDT WED APR 8 2015

.UPDATE...945 PM...
IMPROVED NEAR THE LAKESHORE THIS EVENING I AM
A BIT HESITANT TO DROP THE ONGOING FOG ADVISORY...AS CONDITIONS
COULD FAVOR IT TO REDEVELOP OVERNIGHT. IT STILL APPEARS THAT AS
THE WARM FRONT AND HIGH DEW POINT AIR BEGINS TO LIFT NORTHWARD
INTO THE COLDER AIR MASS OVER NORTHERN ILLINOIS OVERNIGHT THAT FOG
COULD REDEVELOP OVER THE AREA. FOR THIS REASON...I WILL LEAVE THE
ADVISORY IN PLACE.

IT STILL APPEARS MUCH OF THE AREA WILL BE IN LINE FOR THUNDERSTORM
ACTIVITY OVERNIGHT. RADAR IMAGERY IS INDICATING WIDELY SCATTERED
CELLS TRYING TO DEVELOP ACROSS EASTERN IOWA AND WESTERN ILLINOIS
ASSOCIATED WITH INCREASING WARM ADVECTION. THE 00 UTC SOUNDINGS
OUT OF KDVN AND KILX INDICATED THE PRESENCE OF VERY STEEP MID-
LEVEL LAPSE RATES ASSOCIATED WITH AN EML. HOWEVER...MOISTURE WAS
LACKING A ABOVE THE INVERSION...LIMITING THE ELEVATED CAPE. THIS
SEEMS TO BE WHY THE ACTIVITY IS SLOW TO DEVELOP NORTH OF THE WARM
FRONTAL BOUNDARY. HOWEVER...WITH A 40+ KT LOW LEVEL JET EXPECTED
TO CONTINUE SETTING UP...MOISTURE TRANSPORT SHOULD RESULT IN A
RAPID MOISTENING AROUND 850 MB BENEATH THESE STEEP MID LEVEL
LAPSE RATES...LIKELY RESULTING IN AN UPTICK IN CONVECTIVE
DEVELOPMENT OVER NORTHERN ILLINOIS OVERNIGHT. THE MAIN THREAT
WITH THIS ACTIVITY WILL BE SOME HEAVY DOWN POURS AND HAIL.

KJB

 

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The warning for the cell moving into McHenry County.

 

 

SEVERE THUNDERSTORM WARNING
ILC007-037-089-111-090515-
/O.NEW.KLOT.SV.W.0004.150409T0435Z-150409T0515Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1135 PM CDT WED APR 8 2015

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
NORTHEASTERN DE KALB COUNTY IN NORTH CENTRAL ILLINOIS...
SOUTHEASTERN BOONE COUNTY IN NORTH CENTRAL ILLINOIS...
SOUTHWESTERN MCHENRY COUNTY IN NORTHEASTERN ILLINOIS...
NORTHWESTERN KANE COUNTY IN NORTHEASTERN ILLINOIS...

* UNTIL 1215 AM CDT

* AT 1134 PM CDT...A SEVERE THUNDERSTORM WAS LOCATED NEAR KINGSTON...
OR NEAR GENOA...MOVING NORTHEAST AT 25 MPH.

HAZARD...QUARTER SIZE HAIL.

SOURCE...RADAR INDICATED.

IMPACT...DAMAGE TO VEHICLES IS EXPECTED.

* LOCATIONS IMPACTED INCLUDE...
BELVIDERE...WOODSTOCK...MARENGO...GENOA...LAKE IN THE HILLS...
HUNTLEY...HAMPSHIRE...LAKEWOOD...KIRKLAND...KINGSTON AND UNION.

INCLUDING THE FOLLOWING INTERSTATE...
I-90 BETWEEN MILE MARKERS 36 AND 54.

 

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Half awake as this thing keeps cracking and I'll be just as good as a soothsayer but 'upstream' radar doesn't really look all that foreboding at this early hour once current cells move on out.

Clear-out come morning or a grungy start still in the cards?

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DAY 1 CONVECTIVE OUTLOOK  

NWS STORM PREDICTION CENTER NORMAN OK  

1244 AM CDT THU APR 09 2015  

 

VALID 091200Z - 101200Z  

   

..THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF NE TX  

FAR SE  

OK...NRN LA...AR...NW MS...WRN TN...KY...SE MO...IL...FAR SRN  

WI...IND AND WRN OH...  

 

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN  

PLAINS...LOWER TO MID MS VALLEY...OZARKS...OH VALLEY...SRN GREAT  

LAKES AND CNTRL APPALACHIAN MTNS...  

 

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE SRN  

PLAINS...LOWER TO MID MS VALLEY...OZARKS...TN VALLEY...OH  

VALLEY...SRN GREAT LAKES AND CNTRL APPALACHIANS...  

   

..SUMMARY  

 

SEVERE THUNDERSTORMS ARE LIKELY TODAY INTO TONIGHT FROM PARTS OF THE  

SOUTHERN PLAINS...NORTHEASTWARD INTO THE LOWER TO MID MISSISSIPPI  

VALLEY...OHIO VALLEY AND SOUTHERN GREAT LAKES REGION. THIS WILL  

INCLUDE THE RISK FOR DAMAGING WIND GUSTS AND LARGE HAIL. A FEW  

TORNADOES MAY OCCUR WITH A STRONG TORNADO POSSIBLE.  

   

..OH VALLEY/SRN GREAT LAKES/CNTRL APPALACHIANS  

 

AN UPPER-LEVEL TROUGH WILL MOVE QUICKLY EWD ACROSS THE CNTRL AND NRN  

PLAINS TODAY AS A SFC LOW MOVES NEWD INTO THE UPPER MS VALLEY. A  

TRAILING COLD FRONT WILL MOVE EWD INTO THE MID MS VALLEY THIS  

AFTERNOON. A WARM FRONT IS FORECAST TO MOVE NWD INTO THE SRN GREAT  

LAKES...ALONG WHICH SCATTERED THUNDERSTORMS MAY BE ONGOING THIS  

MORNING. CONVECTIVE COVERAGE SHOULD GRADUALLY INCREASE ACROSS THE OH  

VALLEY AND SRN GREAT LAKES REGION DURING THE DAY AS A LOW-LEVEL JET  

MOVES INTO THE REGION FROM THE SOUTHWEST. STRENGTHENING WARM  

ADVECTION AND SFC HEATING MAY RESULT IN POCKETS OF MODERATE  

INSTABILITY BY EARLY AFTERNOON. AS THE COLD FRONT SWEEPS EWD ACROSS  

THE MID MS VALLEY THIS AFTERNOON...SFC-BASED THUNDERSTORMS SHOULD  

DEVELOP ALONG AND AHEAD OF THE FRONT WITH OTHER CELLS INITIATING EWD  

ACROSS THE WARM SECTOR IN THE OH VALLEY. THE DEVELOPMENT OF SEVERAL  

LINE SEGMENTS OR A SEMI-CONTINUOUS SQUALL LINE MAY OCCUR FROM THE  

LATE AFTERNOON INTO THE EVENING ACROSS THE REGION.  

 

NAM FORECAST SOUNDINGS AT 00Z/FRIDAY FROM ST LOUIS NEWD TO  

INDIANAPOLIS SHOW MLCAPE VALUES OF 1000 TO 1500 J/KG WITH SFC  

DEWPOINTS IN THE LOWER 60S F. THIS COMBINED WITH 40 TO 50 KT OF FLOW  

JUST ABOVE THE BOUNDARY LAYER SHOULD SUPPORT SEVERE STORMS WITH WIND  

DAMAGE POTENTIAL. LINE SEGMENTS THAT CAN ORGANIZE IN AREAS WHERE  

INSTABILITY BECOMES MAXIMIZED COULD DEVELOP AN ENHANCED WIND-DAMAGE  

THREAT. THE SHEAR ENVIRONMENT SHOULD ALSO SUPPORT SUPERCELL  

DEVELOPMENT BUT THIS WILL DEPEND UPON THE PREFERRED STORM MODE. THE  

MOST FAVORABLE AREA FOR SUPERCELLS WOULD BE IN CNTRL AND NRN IL  

WHERE THE LOW AND MID-LEVEL JET IS FORECAST TO COUPLE JUST AHEAD OF  

A VORTICITY MAX. ANOTHER AREA OF POTENTIAL FOR SUPERCELLS COULD BE  

ACROSS THE OH VALLEY WHERE CELLS MAY TEND TO BE DISCRETE AND MODELS  

FORECAST A POCKET OF MODERATE INSTABILITY. ANY SUPERCELL THAT CAN  

ORGANIZE WILL HAVE POTENTIAL FOR HAIL AND POSSIBLY TORNADOES. A  

STRONG TORNADO CAN NOT BE RULED OUT ACROSS THE REGION BUT THIS  

SHOULD DEPEND ON MESOSCALE FACTORS. DUE TO UNCERTAINTY CONCERNING  

THE LOCATION...WILL DEFER TO LATER OUTLOOKS.  

 

FURTHER SOUTHEAST...AN ISOLATED SEVERE THREAT MAY ALSO DEVELOP  

ACROSS THE CNTRL APPALACHIAN MTNS BUT ANY POTENTIAL FOR WIND DAMAGE  

WOULD LIKELY BE LESS WITH SEWD EXTEND DUE TO WEAKER LOW-LEVEL FLOW.  

   

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