Rockford Scanner™: Severe Thunderstorm Warning

Rockford Scanner



 


Severe Thunderstorm Warning

BULLETIN – IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Chicago/Romeoville Il
1053 PM CDT SAT SEP 1 2018

The National Weather Service in Chicago has issued a

* Severe Thunderstorm Warning for…
Central Ogle County in north central Illinois…
Southwestern Winnebago County in north central Illinois…

* Until 1145 PM CDT

* At 1053 PM CDT, severe thunderstorms were located along a line
extending from near German Valley to near Mount Morris to near
Oregon, moving northeast at 35 mph.

HAZARD…60 mph wind gusts.

SOURCE…Radar indicated.

IMPACT…Expect damage to roofs, siding, and trees.

* Severe thunderstorms will be near,
Byron around 1105 PM CDT.
Pecatonica around 1110 PM CDT.
Winnebago and Stillman Valley around 1120 PM CDT.
Rockford and Rockford Airport around 1125 PM CDT.
Loves Park around 1145 PM CDT.

Other locations impacted by these severe thunderstorms include Davis
Junction, Leaf River, New Millford and Adeline.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

For your protection move to an interior room on the lowest floor of a
building.

Torrential rainfall is occurring with these storms, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.





Rockford Scanner™: Severe Thunderstorm Watch

Rockford Scanner



NWS Storm Prediction Center Norman OK
730 PM CDT Tue Aug 28 2018

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of
Northeastern Illinois, Extreme northwestern Indiana, and Lake Michigan

* Effective this Tuesday night from 730 PM until Midnight CDT.

* Primary threats include…
Scattered damaging wind gusts to 70 mph possible
Isolated large hail events to 1.5 inches in diameter possible

SUMMARY…

A well-developed bow echo (now crossing the Mississippi
River from Iowa into northwestern Illinois) should persist for
another few hours while moving across northern/northeastern
Illinois, immediately north of a residual outflow boundary. The
bowing segment will be accompanied by a continued threat for
damaging winds, and perhaps some hail with the strongest embedded
updrafts.

The severe thunderstorm watch area is approximately along and 45
statute miles north and south of a line from 60 miles southwest of
Rockford IL to 90 miles east northeast of Marseilles IL. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU9).

PRECAUTIONARY/PREPAREDNESS ACTIONS…

REMEMBER…A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.








Rockford Scanner™: Severe Thunderstorm Watch

Rockford Scanner



The Storm Prediction Center (SPC) has issued a Severe Thunderstorm Watch for Northern and Central Illinois until 8 pm tonight.  Scattered damaging wind up to 70 mph is possible, including isolated hail up to lime size, and frequent lightning.  Please have multiple ways of receiving weather alerts this evening and bring in or tie down any loose items that might be in your backyards.

SUMMARY...Scattered thunderstorms will are developing over western
   Illinois and will spread across the watch area through the
   afternoon.  The most intense cells will pose a threat of damaging
   wind gusts and hail.

   The severe thunderstorm watch area is approximately along and 60
   statute miles east and west of a line from 50 miles east northeast of Rockford IL to 55 miles west southwest of Mattoon IL. For a complete depiction of the watch see the associated watch outline update.

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Severe Thunderstorm Watch means conditions are
   favorable for severe thunderstorms in and close to the watch area.
   Persons in these areas should be on the lookout for threatening
   weather conditions and listen for later statements and possible
   warnings. Severe thunderstorms can and occasionally do produce
   tornadoes.

 








Rockford Scanner™: Severe Thunderstorm Watch Likely For Parts of Illinois

Rockford Scanner



The Storm Prediction Center (SPC) has issued a mesoscale discussion (MD) for a large portion of Northern and Central Illinois, which you can read below.

In short, there is an 80% chance of an issuance for a Severe Thunderstorm Watch, so a watch is likely in the next hour or two.  Damaging winds looks to be the main threat.

 

   Mesoscale Discussion 0974
   NWS Storm Prediction Center Norman OK
   1223 PM CDT Sun Jul 01 2018

   Areas affected...Northern and Central Illinois and Far Northwest
   Indiana.

   Concerning...Severe potential...Watch likely 

   Valid 011723Z - 011900Z

   Probability of Watch Issuance...80 percent

   SUMMARY...Strong to severe storms are expected this afternoon across
   northern and central Illinois. The primary threat from these storms will be damaging wind gusts.

   DISCUSSION...Temperatures have risen into the mid to upper 80s
   across much of Illinois with dewpoints in the upper 70s. This has
   led to MLCAPE around 2500 J/kg. Additional destabilization is
   expected through the afternoon as surface heating continues. Storms are expected to form along the cold front (currently in eastern Iowa and Eastern Missouri) and move eastward through the afternoon. Flow is relatively weak on the ILX 12Z sounding, however, low-level flow is forecast to increase to 35 to 40 knots by mid-afternoon. This will lead to a marginal shear environment with effective shear around 25 to 30 knots with most of this shear focused in the lowest 1 to 2 km. Nearly parallel orientation of the cold front to the deeper level flow will limit a greater severe weather threat, however, more robust updrafts could mix down stronger winds, posing a damaging wind threat through the afternoon. The threat will be maximized with any bowing segments which can orient more normal to the low-level flow and accelerate northeastward. A severe thunderstorm watch is likely in the next hour or two to cover this severe wind threat.








Rockford Scanner™: Tornado Watch for Wisconsin

Rockford Scanner



The Storm Prediction Center (SPC) has issued a Tornado Watch for a large portion of Wisconsin until 7 pm tonight.  A couple tornadoes, hail up to lime size, and scattered wind gusts up to 70 mph are possible this afternoon.

Storms will develop ahead of an approaching cold front this afternoon and evening.  A few scattered supercell may form ahead of the cold front and squall line which will pose the greatest threat for tornadoes.

For the Rockford area, we are under a Slight Risk for Severe Weather with damaging winds up to 70 mph and large hail will be the main threat.  Heavy rain and frequent lightning are also possible. These storms are expected to develop and be in the area after 1 pm through about 5 pm this evening.

 








Rockford Scanner™: Do You Know How and What to Report For Severe Weather?

Rockford Scanner





The National Weather Service in Chicago shared a great graphic explaining what to look for  and how to report Severe Weather.  We have shared it below!  We highly suggest submitting severe weather reports, but remember, SAFETY FIRST!

32453870_1784773034913056_7649344416397656064_n-1

 





Rockford Scanner™: Severe Thunderstorm Watch Likely To Be Issued Soon

Rockford Scanner





The Storm Prediction Center issued a mesoscale discussion for parts of the region with a 95% issuance of a Severe Thunderstorm Watch just before 3 pm.  It is possible this watch will be issued just to the South of the Rockford area.  Full discussion is posted below!

mcd0413

Mesoscale Discussion 0413
   NWS Storm Prediction Center Norman OK
   0237 PM CDT Mon May 14 2018

   Areas affected...central/northern IL

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 141937Z - 142030Z

   Probability of Watch Issuance...95 percent

   SUMMARY...Severe thunderstorms are expected to develop across the
   discussion area the remainder of this afternoon with a risk for
   large hail and damaging winds.  A Severe Thunderstorm Watch will be
   issued prior to 20Z.

   DISCUSSION...Latest visible imagery shows deepening cumulus in the
   vicinity of  the front over central/northern IL at 1935Z, and
   modification of the special KDVN sounding for current conditions
   shows little remaining CINH.  Thunderstorms are expected to develop
   and will likely become severe over the next few hours given an
   environment characterized by moderate surface-based instability and
   40-45 kts of deep-layer wind shear. Damaging winds and large hail
   will be possible, and a Severe Thunderstorm Watch will be issued
   prior to 20Z.




Rockford Scanner™: Chance for Severe Weather Again Today

Rockford Scanner





That’s right, we again have a Marginal (1 out of 5) to Slight (2 out of 5) risk for Severe Weather with large hail and damaging winds being the main threat.  The reason for this continued threat over the last fews has been due to a frontal boundary that has stalled out just to our south over Central Illinois.  It is time for a quick lesson in meteorology and storm development.  There are three ingredients that are needed for storm development, just your average storm:

  1. Moisture (dewpoint) [Generally want your dewpoint to be 55F or more, but can vary based on the type of convection]
  2. Instability (CAPE)  [Dependent on the season, but generally 1000 J/kg is ideal]
  3. Source of Lift (Boundary, Front, etc)

For Severe Storm development there is one more ingredient that is needed, and this is the KEY between seeing severe storms and your average thunderstorm.  That fourth ingredient is Shear.  Shear is the change or increase in winds with height and direction.  This can be broken down further into Directional Shear and Speed Shear.  Directional shear is the change of wind direction with height. While Speed shear is the change in wind speed with height.  Shear is important because it helps thunderstorms tilt with height allowing for the storm to sustain itself longer by keeping the updraft separate from the down draft. Which will help with the development of a mesocyclone (rotating updraft that defines a supercell), which can further lead to the development of a tornado if other factors align just right.  For the record, this is really, really dumbed down, and much more goes into this.

If you haven’t fallen asleep yet or stopped reading you might be asking, why does this matter?  Well, for today’s setup, all four of these ingredients need to come together in order for us to see a repeated threat for severe weather.  Generally speaking, dewpoints across the area are around 55F or higher.  The source of lifting, in simple terms, is going to be the boundary just to our south.  The limiting factor right now is our CAPE, which according to the Mesoscale Analysis from the SPC is basically nothing.  That is supposed to increase though this afternoon to between 2000-3000 J/kg, which is more than enough instability.  When it comes to shear, thanks to that boundary, winds at the surface are out of the east.  As we go up with height, between 925-850 mb,  the winds shift to out of the southwest, which means we have great turning with height in our lower levels. Above that at 700 mb, our winds are out of the west and at 500 mb they are out of the west-northwest.  Great shear profile, but because we are north of the boundary, all our storms will be what we like to call elevated and not surfaced based.  This is why we are talking about a large hail threat initially, that could transition to a more straight line wind threat late tonight as winds start to become more parallel, or unidirectional with height (winds are all in one direction).  If the storms were surface based, then we would have a better chance for tornado development, but the storms will be too high off the ground to favor that.

So to summarize, Marginal to Slight risk for severe weather late this afternoon and evening, into the late overnight hours.  An initial round of showers and storms may move through around 4 pm this afternoon with a threat for large hail and wind.  The main focus though is around Midnight as a cluster of showers and storms will enter the Rockford area.  More recent model runs have been trending it around or just after Midnight, so that is something that we will keep an eye on.

I am sorry if this post was too long, I just felt it would be a good time to give a crash course in what it is meteorologist are looking at when it comes to forecasting thunderstorms.  It was also a great excuse for me to talk about today’s severe weather threat while also incorporating a very small amount of Mesoscale Meteorology ahead of my final.

day1otlk_1300-1

 




Rockford Scanner™: Severe Weather Possible Today

Rockford Scanner





There is a Marginal Risk (1 out of 5) for Severe Weather across our area this afternoon and evening, with the main threats being damaging wind and hail.

day1otlk_1300

The line of showers and storms that  moved this morning were associated with the passing of the warm front that will set up to our north in Southern Wisconsin.  Putting us in what we like to call the “warm sector” of the low pressure system center over Northern Iowa.  Our threat for severe weather this afternoon and evening will come with the passing of a cold front as the low pressure tracks to the northeast across Southern and Central Wisconsin.

The latest model runs have isolated thunderstorms developing around 2 pm across North Central Illinois along and just ahead of the previously mentioned cold front (pictured below).

NAMNSTMW_prec_radar_009

 

By 5 pm, a broken line of storms will develop to the east of the Rockford area along that cold front and progress to the east across far Eastern Illinois and Northern Indiana into the evening and overnight hours where the greater threat for damaging winds, hail, and even an isolated tornado can’t be ruled out (pictured below).  The threat for severe weather ending by around 6pm for the Rockford area.

NAMNSTMW_prec_radar_010

Overall the severe threat this afternoon and evening should be