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April 27-29 Severe Threat


snowlover2

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Going off memory but it seems like there is stronger mid-level flow in northern IL on the 00z NAM compared to the last few runs.  OTOH, it seems like the frontal position nudged south.

 

You would be correct. Warm front is now just north of Bloomington, previous runs had it near Rockford.

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Previously there have been two plays: the WF/triple point, and the 850-700 mb speed max.  The WF being modeled farther south opens up the possibility that these overlap, maybe somewhere around Decatur, and all that being under the let exit region of our jet, well, that makes things interesting.

 

This isn't modeled yet, but it's an interesting possibility.  A discrete storm feeding of low-level helicity from the WF and stronger mid/upper level winds from farther south could be a tornado-producer.

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With the warm front being modeled farther south tomorrow I'm more optimistic I won't get called into work and will be able to chase. Going with Gilbert from NIU, a NIU grad and another LOT forecaster. Plan is to head down to CMI in the morning and assess.

Sent from my SCH-I535

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With the warm front being modeled farther south tomorrow I'm more optimistic I won't get called into work and will be able to chase. Going with Gilbert from NIU, a NIU grad and another LOT forecaster. Plan is to head down to CMI in the morning and assess.

Sent from my SCH-I535

 

 

What are your thoughts on the farther south placement tomorrow?  Normally I'd be skeptical since the morning activity looks to make fairly steady progress north/east but with the system basically being stalled/occluded, just might not be much of an impetus to get that boundary northward quickly?

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What are your thoughts on the farther south placement tomorrow? Normally I'd be skeptical since the morning activity looks to make fairly steady progress north/east but with the system basically being stalled/occluded, just might not be much of an impetus to get that boundary northward quickly?

Still thinking it'll make it about to a BMI to north of LAF corridor, so into the southern LOT and IWX CWA. Right now right the front is on the doorstep of CMI and through PIA. We're heading down to SPI to assess options.
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Decided not to chase today based on the conditional environment and a 5 hour drive, but with that said I could see some decent storms in Illinois.

Some favorable factors:

-plenty of clearing to help with destabilization

-impressive mid-level lapse rates

-Near the nose of 500 jet

-decent low level turning

Unfavorable factors:

-moisture is scoured (upper 50s dewpoints) with no recovery anticipated

-veer/back/veer profile not great for discreet convection

-winds continue to veer. This will lessen low level srh.

With that being said...I would be chasing just south of the warm front where winds remain backed and LCL values are lower

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Decided not to chase today based on the conditional environment and a 5 hour drive, but with that said I could see some decent storms in Illinois.

Some favorable factors:

-plenty of clearing to help with destabilization

-impressive mid-level lapse rates

-Near the nose of 500 jet

-decent low level turning

Unfavorable factors:

-moisture is scoured (upper 50s dewpoints) with no recovery anticipated

-veer/back/veer profile not great for discreet convection

-winds continue to veer. This will lessen low level srh.

With that being said...I would be chasing just south of the warm front where winds remain backed and LCL values are lower

 

Thanks for the analysis. Due to work obligations, I won't be driving down there.

 

OT, but is your avatar Henryville?

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Recent AFD's for western IL. 

 

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
1136 AM CDT Mon Apr 28 2014

.UPDATE:
Issued at 1135 AM CDT Mon Apr 28 2014

Large cumulus field has recently developed across central Missouri
in convergence zone just ahead of surface cold front/dryline.
Environment is becoming increasing unstable with latest 16Z SPC
MLCAPES showing 500-1000 J/kg over central and eastern Missouri
with little CINH right ahead of the front. Current thinking is
that thunderstorms will develop in the next hour or two right
ahead of the the front and move east and northeast across eastern
Missouri into Illinois during the afternoon hours. Severe threat
including hail and damaging winds continues given the increasing
instability and impressive deep layer shear. Also, 0-1km SRH
values are currently between 100 and 250 across eastern Missouri
and Illinois support an isolated tornado risk.

Britt

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1134 AM CDT MON APR 28 2014

.UPDATE...
ISSUED AT 1126 AM CDT MON APR 28 2014

THE FRONTAL BOUNDARY IS ROUGHLY ALONG A KTQE...KAWG...TO KCMI LINE
AT 16Z AND IT HAS NOT MOVED FOR SEVERAL HOURS.

TRENDS IN THE RAP INDICATE VERY LITTLE IN THE WAY OF MOMENT OF
THIS FRONTAL BOUNDARY THIS AFTERNOON. IF CORRECT...ROUGHLY THE
NORTHERN HALF OF THE AREA WILL REMAIN IN THE 50S WITH THE HWY 20
CORRIDOR POSSIBLY STRUGGLING TO REACH 50.

SATELLITE TRENDS INDICATE THERMALS ARE ACTIVE WHICH HAS ALLOWED CU
TO DEVELOP ALONG/AHEAD OF THE COLD FRONT ACROSS MISSOURI.

CONVECTION SHOULD DEVELOP WITHIN A FEW HOURS FROM CENTRAL INTO
SOUTHERN MISSOURI ALONG THE FRONT AND MOVE NORTHEAST.
PRECIPITATION CHANCES SHOULD THEREFORE BE ON THE INCREASE STARTING
AROUND MID AFTERNOON ACROSS THE AREA.

 

Peoria met. says ILX is doing a 18z sounding

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Thanks for the analysis. Due to work obligations, I won't be driving down there.

 

OT, but is your avatar Henryville?

Yes it is. Was about 3/4 mile south of henryville as it went through.

Noticed spc took 5% tor west with this outlook. Not surprised given the slow progression of this system

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Hopefully tomorrow will clear out enough for potential severe weather in the Lower GL. Seems almost foreign after months of snow 

Severe storm parameters may get interesting tomorrow afternoon if it warms up to about 70F at IN/OH/MI borders. The NAM forecast sounding shows 10C/km lapse rate and 50 kt at 700mb tomorrow. That's about a 30kt difference between the surface and 700mb.

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