May 27-June 2 Severe Weather

[Hoosier]

Severe threat looks to get going by Tuesday and likely ramp up toward the end of next week. Still too early for day to day details but the large scale pattern looks to be slow to break down which means multiple rounds of severe or at least chances for severe for some areas. At this point, it looks like maybe the NW 1/2 or so of the subforum would be most favored for repeated action in this type of pattern. Discuss.

[Stebo]

The NW portion of the region looks to have the best chances, locally Tuesday is of interest at least for now, the later in the week stuff does have a high ceiling however.

 

The new day 3

 

 

 

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0229 AM CDT SUN MAY 26 2013

 

VALID 281200Z - 291200Z

 

...THERE IS A SLGT RISK OF SVR TSTMS FOR A LARGE PORTION OF THE PLAINS EASTWARD INTO THE WESTERN GREAT LAKES...

 

...SYNOPSIS... THE UPPER PATTERN ON TUESDAY IS CHARACTERIZED AS COMPROMISING OF SEVERAL SHORTWAVE IMPULSES EMBEDDED WITHIN BROAD SWLY FLOW OVER THE PLAINS/MIDWEST DOWNSTREAM OF AN AMPLIFYING WRN U.S. UPPER TROUGH. A SURFACE LOW OVER THE CNTRL HIGH PLAINS WILL REMAIN QUASI-STATIONARY AS MOIST SLY LOW LEVEL FLOW INTENSIFIES --E OF A NORTH-SOUTH DRYLINE-- FROM TX NWD INTO THE CNTRL PLAINS AND MIDWEST DURING THE PERIOD. A WARM FRONTAL ZONE IS FORECAST TO ADVANCE NWD OVER A PORTION OF THE MIDWEST AND INTO THE GREAT LAKES REGION. FARTHER W...A SURFACE TROUGH WILL EXTEND TO ANOTHER LOW OVER WY.

 

...PLAINS... STRENGTHENING H5 FLOW OVER A LARGE PORTION OF THE PLAINS AND WIDESPREAD MID 60S BOUNDARY LAYER DEWPOINTS E OF THE DRYLINE WILL POTENTIALLY BE MORE FAVORABLE FOR STRONG/SEVERE STORMS TUESDAY COMPARED TO PRIOR DAY/S. MODELS SHOW A PLUME OF STEEP H7-H5 LAPSE RATES /IN EXCESS OF 8 DEG C/KM/ ENVELOPING A LARGE PART OF THE SRN-CNTRL PLAINS INTO THE MID MO VALLEY REGION. COUPLED WITH STRONG DIURNAL HEATING IN WAKE OF ANY EARLY DAY TSTM ACTIVITY --MOST LIKELY OVER THE MID-LOWER MO VALLEY-- WILL PROBABLY RESULT IN A MODERATE TO VERY UNSTABLE AIRMASS BY PEAK HEATING /2000-3500 J/KG MLCAPE/. ORGANIZED STRONG-SEVERE STORMS CAPABLE OF LARGE HAIL/DMGG WINDS AND A FEW TORNADOES WOULD BE POSSIBLE WITH THE MORE INTENSE SUPERCELLS/LINEAR STRUCTURES. A 50 KT LLJ IS FORECAST TO DEVELOP OVER THE CNTRL PLAINS BY EVENING...AND LIKELY AID IN SUSTAINING AN ISOLD SEVERE THREAT INTO THE OVERNIGHT.

 

...MIDWEST/WRN GREAT LAKES... A BELT OF STRONG SWLY H85 FLOW WILL SERVE AS THE PRIMARY IMPETUS FOR INCREASING LOW LEVEL MOISTURE WITH DEWPOINTS RISING INTO THE 60S. THIS WILL OCCUR COINCIDENT WITH A NWD ADVANCING WARM FRONT AND RESULT IN A DESTABILIZING AIRMASS. ISOLD OCCURRENCES OF LARGE HAIL AND DMGG WINDS WILL BE THE PRIMARY THREATS WITH THESE STORMS...BUT A FEW TORNADOES ARE POSSIBLE...ESPECIALLY IF SURFACE-BASED STORMS CAN DEVELOP/ROOT NEAR THE WARM FRONT IN A STRONGER LOW LEVEL SHEAR ENVIRONMENT.

 

Personally I do think that stuff along the warm front will be surface-based, especially across WI maybe even Lower MI.

[Hoosier]

The CIPS analogs off the 00z GFS for the end of the week are a who's who of severe weather dates. It at least shows what the higher end potential looks like.

[Hoosier]

12z NAM suggests that Tuesday's slight risk may eventually need to be expanded south.

[Powerball]

12z NAM suggests that Tuesday's slight risk may eventually need to be expanded south.

 

So does the GFS.

[tornadotony]

6/2/90 is a top analog on this morning's CIPS run for Friday.

 

http://www.eas.slu.edu/CIPS/ANALOG/stats.php?reg=MV&model=GFS212&fhr=F132&flg=

[Stebo]

6/2/90 is a top analog on this morning's CIPS run for Friday.

 

http://www.eas.slu.edu/CIPS/ANALOG/stats.php?reg=MV&model=GFS212&fhr=F132&flg=

 

Not a shock here, too bad that the CIPS don't go back to 1965 or 1953, I bet they'd be in the mix as well as there are some similarities.

[Hoosier]

Forecast soundings look fairly impressive in the Lakes/northern Ohio Valley on Tuesday...strongly sheared with moderate instability. Not only is there a threat for some tornadoes but you could probably even make an argument for an isolated strong tornado.

[Hoosier]

00z NAM for KLAF valid 21z Tuesday

 

 

[Chicago Storm]

Unfortunately due to work I won't be able to travel west until mid-week.

 

On the plus side I have morning shifts, so I'll be able to play any threat in the local/regional area Mon-Wed...With Tue looking like the only interesting day in that period.

[Stebo]

Forecast soundings look fairly impressive in the Lakes/northern Ohio Valley on Tuesday...strongly sheared with moderate instability. Not only is there a threat for some tornadoes but you could probably even make an argument for an isolated strong tornado.

 

Tuesday is quickly becoming very interesting in my eyes, both the NAM and GFS are pretty much lock step on a potential along the warm front that day with good instability and very good wind shear. In some cases the winds go from due south at surface to southwest at 850 to northwest at 500mb.

[Stebo]

Unfortunately due to work I won't be able to travel west until mid-week.

 

On the plus side I have morning shifts, so I'll be able to play any threat in the local/regional area Mon-Wed...With Tue looking like the only interesting day in that period.

 

Wednesday isn't bad either, though I do think it would be north or west of your immediate area, WI or IA

[cyclone77]

Unfortunately due to work I won't be able to travel west until mid-week.

 

On the plus side I have morning shifts, so I'll be able to play any threat in the local/regional area Mon-Wed...With Tue looking like the only interesting day in that period.

 

I hear ya on the work related limitations.  Timing of work days that I couldn't get out of have really screwed me so far this year.  Love my job but it's not as flexible as I'd like regarding time off work with less than a week's notice.  With that being said I'll be out in the Plains Wed-Fri, after leaving Tue afternoon. 

 

Models are still sort of figuring things out timing wise with the evolution of shortwaves, etc but it looks like much of the sub will have some severe risk later on this week. 

[Stebo]

Yeah the job limitation is going to stink as I work Tuesday, though who knows maybe I see something here lol. Then I am working Friday/Saturday Nights which shoots those 2 days.

[Brewers]

Sucks that my summer job starts this week, which prevents me from chasing too far from home. At least the GFS is looking pretty good  Tuesday evening around southern WI so I wont have to stray too far.

[Hoosier]

New day 2 outlook not very wordy for the region lol. 30% area kisses western Lake Michigan.

..MIDWEST/GREAT LAKES

STRONG/LOCALLY SEVERE STORMS MAY BE ONGOING AT THE START OF THE DAY 2 PERIOD OVER A PORTION OF THIS REGION IN RESPONSE TO A STRONG LLJ/WAA REGIME FOCUSED INVOF THE WARM FRONT OVER NRN MO/IA/IL. IT APPEARS FEASIBLE THAT SOME OF THIS ACTIVITY MAY CONTINUE --AT LEAST SUPPORTED IN PART BY A MID LEVEL /CONVECTIVELY-AIDED/ IMPULSE-- AS IT MOVES EWD DURING THE DIURNAL HEATING CYCLE. STRONG SWLY H85-H7 FLOW 40-50 KT WOULD SUPPORT SOME POSSIBILITY FOR A FORWARD PROPAGATING MCS AS IT MOVES TOWARDS THE SRN GREAT LAKES.

[Brewers]

[Stebo]

Honestly I know they mentioned a forward propagating mcs but I really think there is a decent tornado potential with this one too that I am surprised they arent making any mention of.

[RCNYILWX]

Honestly I know they mentioned a forward propagating mcs but I really think there is a decent tornado potential with this one too that I am surprised they arent making any mention of.

Agreed, the hodos are pretty impressive.

Sent from my SCH-I535 using Tapatalk 2

[Stebo]

The NAM really paints a tornado potential for Chicago/NW IN and SW MI on the 00z run for Tuesday late afternoon and into the evening. The GFS is pretty similar as well, there is very favorable clockwise turning in the lower 1 and 3km of the atmosphere and to be honest all the way up to the 6km level. I wouldn't be shocked if this potential holds through the next 2 runs that there is an upward tick in the wording/probs for Tuesday on the new Day 2.

[tornadotony]

Yeah I really don't think this is going to be an MCS at least initially.  This is a classic Great Lakes warm-frontal tornado outbreak signal.  You have the warm front hung up somewhere near the southern end of Lake Michigan and a decent jet streak/shortwave trough intersecting it during the afternoon and evening hours.  You don't see much capping to prevent initiation.  The warm front is diffuse, which will allow sfc to near-sfc based convection right along it.  It's classic.  As long as morning activity clears for sufficient destabilization, there's a good chance Chitown and the rest of nrn and cntl IL/nrn IN are in trouble tomorrow.

[harrisale]

Wednesday in southern Ontario is starting to look quite interesting, although some model differences leave me slightly lacking confidence in how big of a day it will be.

 

The NAM shows much better instability (2500-3000 J/Kg) along with better upper wind speeds than the GFS, although both models are showing 25-35 kts of 0-850mb bulk shear (yet better hodographs on the GFS). 250+ m2/s2 0-3km helicity is nice to see on the GFS and NAM. Both models have 65F dewpoints and LCL from 300-700m.

 

Either way I will probably be out there Wednesday and maybe Thursday as well depending on how the models trend.

 

EDIT: Hopefully we get some proper forcing to make use of all this, outflow from previous day's/night's storms may help.

 

[Chicago WX]

A day early, but latest day 1 outlook has expanded the slight risk east...now getting into central and southern Indiana.

 

 

...LOWER-MO/MID-MS VALLEYS INTO OH VALLEY THIS AFTERNOON AND
EVENING...

AN MCV APPEARS TO BE EVOLVING AS OF MID MORNING OVER NERN MO...ON
THE NRN FLANK OF NOCTURNAL MCS ONGOING ACROSS THE LOWER-MO VALLEY.
LOW-LEVEL CONVERGENCE/UPLIFT ALONG THE LEADING EDGE OF MCS COLD POOL
COUPLED WITH DEEPER-LAYER FORCING ASSOCIATED WITH MCV WILL LIKELY
SUPPORT TSTM INTENSIFICATION BY EARLY AFTERNOON ALONG THE ERN FLANK
OF THE SYSTEM. THE EWD MIGRATION OF A SWLY LLJ WILL ENHANCE THE
NEWD FLUX OF AN INCREASINGLY MOIST BOUNDARY LAYER THROUGH THE MID-MS
INTO OH VALLEYS...BENEATH AN EWD-ADVECTING EML...SUPPORTING MODERATE
AFTERNOON INSTABILITY AHEAD OF THE MCS. GIVEN MODESTLY STRONG LOW
TO MIDLEVEL FLOW...THE POTENTIAL WILL EXIST FOR ACCELERATION OF THE
CONVECTIVE SYSTEM WITH A RISK FOR DAMAGING WINDS AND HAIL SPREADING
EWD INTO THE OH VALLEY.

[Hoosier]

Yeah I really don't think this is going to be an MCS at least initially. This is a classic Great Lakes warm-frontal tornado outbreak signal. You have the warm front hung up somewhere near the southern end of Lake Michigan and a decent jet streak/shortwave trough intersecting it during the afternoon and evening hours. You don't see much capping to prevent initiation. The warm front is diffuse, which will allow sfc to near-sfc based convection right along it. It's classic. As long as morning activity clears for sufficient destabilization, there's a good chance Chitown and the rest of nrn and cntl IL/nrn IN are in trouble tomorrow.

That is probably my chief concern...an early show botching things up.

[Hoosier]

early look at tomorrow

[A-L-E-K]

I think it is a safe bet that we'll see tomorrow trend at least a little south.

[Thundersnow12]

Heads up LAF brothers, hoping to get off work early tomorrow just in case something happens.

 

 

 

[Stebo]

I think it is a safe bet that we'll see tomorrow trend at least a little south.

Usually I would say yes but as the low ejects out tonight that should start to lift the warm front Northward, I don't think this will trend South much if at all. I am in reference to what it is showing in the 4km wrf which did trend South from original thoughts. In other words I don't think it will trend South anymore. This does open the door for Wednesday across the region as well.

[snowlover2]

Watch being considered in IL.

 

MESOSCALE DISCUSSION 0818
   NWS STORM PREDICTION CENTER NORMAN OK
   1251 PM CDT MON MAY 27 2013

   AREAS AFFECTED...PARTS OF CENTRAL/SRN IL INTO FAR EAST CENTRAL MO
   AND FAR WRN-SWRN IND

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

   VALID 271751Z - 271915Z

   CORRECTED FOR TYPO IN LAST SENTENCE OF THE SUMMARY AND WORDING IN
   LAST SENTENCE OF THE DISCUSSION.

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...POTENTIAL EXISTS FOR ONGOING STORMS...RECENTLY DEVELOPING
   ALONG A N-S LINE FROM WEST CENTRAL IL INTO EAST CENTRAL MO...TO
   INCREASE IN COVERAGE/BE MAINTAINED WITH EWD EXTENT...WHILE
   ADDITIONAL STORMS DEVELOP INVOF AN E-W ORIENTED WARM FRONT IN
   CENTRAL/SRN IL.  HAIL AND DAMAGING WINDS ARE EXPECTED TO BE THE
   PRIMARY THREATS WITH THE STRONGER STORMS THIS AFTERNOON.  WW
   ISSUANCE IS BEING CONSIDERED FROM FAR EAST CENTRAL MO THROUGH
   CENTRAL/SRN IL TO FAR WRN/SWRN IND.

   DISCUSSION...TRENDS IN RADAR IMAGERY SHOWED THE LEADING EDGE OF THE
   LOWER MO VALLEY MCS EXTENDED FROM FAR WEST CENTRAL IL SWWD INTO
   CENTRAL MO /NEAR KCOU/ TO WEST CENTRAL MO /BATES AND CASS COUNTIES/.
   MEANWHILE...SURFACE ANALYSES INDICATED A WARM FRONT EXTENDING EWD
   FROM WEST CENTRAL TO ERN IL /CLARK COUNTY/ THROUGH SRN IND.  SWLY
   LOW LEVEL WINDS HAVE CONTINUED TO ADVECT MOISTURE NEWD ACROSS THE
   WARM SECTOR WITH SURFACE DEWPOINTS IN THE MIDDLE 60S INVOF THE WARM
   FRONT.  THIS COMBINED WITH ADDITIONAL SURFACE HEATING AND THE ERN
   EXTENT OF STEEP MIDLEVEL LAPSE RATES /7-7.5 C PER KM/ WILL FURTHER
   DESTABILIZE THE ATMOSPHERE WITH AN INCREASE IN INSTABILITY AND
   WEAKENING SURFACE BASED INHIBITION.  THE LATTER FACTOR APPEARS TO BE
   WEAKENING SUFFICIENTLY...GIVEN AN INCREASE IN CU FIELD INVOF THE
   WARM FRONT IN IL PER VISIBLE SATELLITE IMAGERY.

   ASCENT ATTENDANT TO THE EWD MOVING MCV...CURRENTLY MOVING FROM NERN
   MO INTO WEST CENTRAL IL...AND CONVERGENCE ALONG AFOREMENTIONED
   BOUNDARIES WILL SUPPORT ADDITIONAL TSTM DEVELOPMENT THIS AFTERNOON
   AS THE INHIBITION WEAKENS FURTHER.  ALTHOUGH EFFECTIVE BULK SHEAR IS
   NOT TOO STRONG YET...35-45 KT WSWLY MIDLEVEL FLOW ALONG THE SRN
   PERIPHERY OF THE MCV WILL SPREAD EWD SUPPORTING AN INCREASE IN BULK
   SHEAR FOR ORGANIZED STORMS.

   ..PETERS/MEAD.. 05/27/2013

 

 

[A-L-E-K]

Usually I would say yes but as the low ejects out tonight that should start to lift the warm front Northward, I don't think this will trend South much if at all. I am in reference to what it is showing in the 4km wrf which did trend South from original thoughts. In other words I don't think it will trend South anymore. This does open the door for Wednesday across the region as well.

 

 

I'm banking on an overnight MCS traversing similar grounds and helping to hang the front up a little further south, if it doesn't happen, north of I80 would be in play