March 15/16 Severe Wx

[The_Global_Warmer]

So the euro shows?

[tornadohunter]

So the euro shows?

Euro shows a 1002 primary low just north of minnesota/nd broder. 

 

Shows a 998 low over davenport. 

 

Cape and dews are about the same as prior runs from what ive seen. 

 

Surface wind field in agreement with nam.. 

 

IMO, leaves a lot to be desired. 

[Stebo]

Euro shows a 1002 primary low just north of minnesota/nd broder. 

 

Shows a 998 low over davenport. 

 

Cape and dews are about the same as prior runs from what ive seen. 

 

Surface wind field in agreement with nam.. 

 

IMO, leaves a lot to be desired. 

The wind fields are better than the NAM especially by 00z and 06z, it also doesn't lose instability as quickly moving east as of 06z.

[IllinoisWedges]

Question for you all, do any of you use the NAMRR? Basically, a higher resolution NAM. 3k NAM. 

 

If not, here's the link: http://www.emc.ncep.noaa.gov/mmb/jcarley/namrr/CONUSNEST/18/CONUSNEST_Great_Lakes_refc.php 

[RyanDe680]

Moisture and storm morphology is what will define Tuesday.

 

+1 - what Hoosier mentioned earlier

[A-L-E-K]

zzzzzzzzzzzzzzz

 

 

decaying sub-severe broken line for mby

[RCNYILWX]

This is an RC / Stebo question - during days where severe weather is forecasted such as what Tuesday is looking to be, how many mets are in the office during an outbreak like that? Are your shifts longer than usual? And does the SPC advise on watches/warnings?

For a well forecast event, we may have up to 10 mets (and sometimes as much as 12). 1 or 2 radar teams of primary and assistant. A mesoanalyst examining obs and mesoanalysis for environmental potential, also the near storm/storm behavior and writing meso AFDs. A severe weather coordinator (sometimes 2 coordinators for major events) working with the warning teams to make sure update statements are timely and passing on important report info that could be used in updates. An aviation forecaster handling TAFs and heads up calls to the airports. A public forecaster doing any routine products that need to be done. Data desk of 1 or 2 handling LSRs and making sure warnings go out on the weather radio. For bigger events we also try to have a social media desk as well that may be covered by a student volunteer when possible. A HAM radio desk is also staffed with 1-3 HAMs to monitor amateur radio as well as our social media pages for reports.

The shift can end up being a marathon, sometimes 12 hours or more, especially if we don't have a lot of extra staffing available (people off but available to come in). I've been at the office from the early morning to the late evening for some of our biggest events in recent years, such as 11/17/13, 4/9/15 and 6/22/15.

Regarding watches, the SPC internally draws up an area they would like to issue a watch for and then initiates a conference call with affected WFOs to discuss counties in the watch and reasoning. During the coordination, counties may be added or removed from the preliminary drawn up watch. Once collaboration is done, the watch is issued and local extensions/adding of counties are handled by the WFOs. All warnings are handled by the WFOs but mesoscale discussions may be helpful for the mesoanalyst and warning team (s).

[andyhb]

If the 12z 4 km NAM verifies and we see 65+ Tds into central IL/IN Tuesday evening, I'll pretty much eat my hat.

[Jim Martin]

 

To what Andy was referring to. East Central Illinois tomorrow evening off the 12z 4k NAM.

[Hoosier]

12z runs look pretty good.  NAM seems to have fixed its weakness in the 700 mb winds that was present last night.

[A-L-E-K]

looks good for north central Illinois

[Hoosier]

looks good for north central Illinois

 

 

I think your area up toward Geos is doubtful...can't rule out severe but the favored area (and best tornado threat) would appear to be generally south of I-88. 

[A-L-E-K]

I think your area up toward Geos is doubtful...can't rule out severe but the favored area (and best tornado threat) would appear to be generally south of I-88. 

 

 

non-starter IMBY but we were never really in the game for severe

 

should be chase worthy nearby though

[rolltide_130]

I don't know how many of you guys pay much attention to the WRF-ANW and the WRF-NNM, but from what I've heard they did very well with the Arkansas event yesterday. 

 

With that said, there is still a lot of spread between the two of them. ANW keeps the DP's below 60 and the NNM has them up to about 64 across C IL Tuesday afternoon and into the evening. 

[Thundersnow12]

Yikes 

 

[Indystorm]

Isn't it a known bias that the NAM tends to overestimate dewpoints?  It seems this has been the case for years even with tweaks and upgrades. What is concerning, however, is that this model run should have better and more recent data.

[Geos]

I think your area up toward Geos is doubtful...can't rule out severe but the favored area (and best tornado threat) would appear to be generally south of I-88. 

 

Yeah that SE flow keeping on going with the approach of storms. Maybe like April 9th, I'll see some hail. 

 

Yikes. 

 

[Hoosier]

GFS keeps the 60 degree dewpoints mainly south of I-70.  Splitting the difference would bring it into LOT's southern tier.

[Hoosier]

Yeah that SE flow keeping on going with the approach of storms. Maybe like April 9th, I'll see some hail. 

 

 

 

Decent MUCAPE/steep lapse rates should allow for hail threat if nothing else.  Really the main issue is magnitude of surface based instability with models indicating it drops off quite quickly in the northeast corner of Illinois.

[cyclone77]

Don't really have too much to add to the disco, as you guys have done a good job pointing everything out.  I will say that I continue to be concerned for the DVN area, especially on the IL side.  Looks like initiation should take place in extreme eastern Iowa around 3-4pm, and quickly mature into a broken line of sups.  I'll be stuck at work till 4 (like usual lol), so may be a bit late to the game for chasing.  If I were off I'd probably hangout near Princeton IL.  I really like the Toulon-Rochelle-Pontiac-Peoria area.

 

Excellent disco from DVN...

 

MODELS DIFFER ON THE EVOLUTION OF THIS SYSTEM AS IT ENTERS THE
MIDWEST ON TUESDAY. THE ECMWF IS THE MOST OMINOUS WITH A DEEPER
NEGATIVELY-TILTED TROUGH AND RAPID CYCLOGENESIS AS WE GET UNDER THE
LEFT EXIT REGION OF THE JET. AS THE CYCLONE BEGINS TO DEEPEN THIS
WILL HANG UP THE COLD FRONT INITIALLY JUST ENOUGH TO ALLOW A DECENT
TRANSPORT OF WARM MOIST AIR INTO THE DVN CWA...AHEAD OF THE FRONT.
THIS WILL ALSO ALLOW FOR BACKING OF THE SURFACE WINDS ESPECIALLY
FROM ABOUT THE MS RIVER AND ON ACROSS NORTHERN IL. THE FRONT WILL BE
ARRIVING AT PEAK HEATING AND WITH A VERY COLD POCKET ALOFT THIS WILL
STEEPEN THE LAPSE RATES CONSIDERABLY. MOST OF THE MODEL DATA
SUGGESTS STRONG DEEP LAYER SHEAR AND SBCAPES OF 2000 J/KG AS
TEMPERATURES RISE INTO THE LOWER 70S. MID LEVEL WINDS WILL ALSO BE
STRENGTHENING TO 50-60 KNOTS. THIS WOULD BE THE WORST CASE SCENARIO
WITH THE POTENTIAL FOR VERY LARGE HAIL...DAMAGING WINDS AND SEVERAL
TORNADOES. LOOKING AT HOW STRONG THE SYSTEM IS THE ECMWF ALSO SEEMS
THE MOST PLAUSIBLE. MAXIMUM TEMPERATURES WILL BE IN THE 60S TO LOWER
70S. SURFACE DEWPOINTS ARE EXPECTED TO CLIMB INTO THE MID 50S FROM
ABOUT THE MS RIVER ON EAST.

[Stebo]

non-starter IMBY but we were never really in the game for severe

 

should be chase worthy nearby though

I wouldn't completely rule out severe weather, even with the lake, hail doesn't care about a surface inversion especially if the storms are well established and become elevated as they move in.

 

Edit: I see a few others also mentioning this for their areas near the lake, I agree.

[Hoosier]

Sort of a tricky call here...I like my chances more than Geos/Alek's area but would rather be farther west.  Timeframe is looking like 0z-3z so just after dark, but system should be deepening and wind fields should be increasing.  Also, what is storm mode like by that time...is it more discrete/broken line or solid line.

[A-L-E-K]

I wouldn't completely rule out severe weather, even with the lake, hail doesn't care about a surface inversion especially if the storms are well established and become elevated as they move in.

 

Edit: I see a few others also mentioning this for their areas near the lake, I agree.

 

 

there is clearly a low threat for low-end severe weather along the lake but it's hardly worth talking about considering excellent tornado chances further west

[Hoosier]

The 1730z discussion mentions the moisture question

 

 

DAY 2 CONVECTIVE OUTLOOK    NWS STORM PREDICTION CENTER NORMAN OK  1200 PM CDT MON MAR 14 2016    VALID 151200Z - 161200Z     ..THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN IA...SRN WI  MUCH  OF IL AND INDIANA...WRN OH AND SWRN LOWER MI...NRN KY...    ...THERE IS A MRGL RISK OF SVR TSTMS IMMEDIATELY SURROUNDING THE  SLIGHT RISK AREA...     ..SUMMARY    SCATTERED SEVERE STORMS ARE LIKELY FROM EASTERN IOWA ACROSS MUCH OF  ILLINOIS...SOUTHERN WISCONSIN AND INDIANA...WITH MORE ISOLATED  ACTIVITY ACROSS NORTHERN KENTUCKY...SOUTHERN LOWER MICHIGAN AND  WESTERN OHIO. THE PRIMARY THREAT WILL BE LARGE HAIL...WITH AN  ISOLATED TORNADO POSSIBLE AS WELL.     ..SYNOPSIS    A POTENT SHORTWAVE TROUGH WILL DEVELOP INTO THE MO AND MID-MS RIVER  VALLEYS DURING THE DAY...AND EJECT NEWD ACROSS THE MIDWESTERN STATES  AND LOWER GREAT LAKES BY WED MORNING. AT THE SURFACE...A LOW  PRESSURE TROUGH WILL INITIALLY EXTEND FROM SRN MANITOBA TO KANSAS  CITY...AND WILL TILT NEWD TO A WRN WI TO CNTRL IL LINE BY 00Z. AHEAD  OF THIS DEVELOPING TROUGH...SLY LOW-LEVEL WINDS WILL BRING MID TO  UPPER 50S F DEWPOINTS NWD TO A WARM FRONT WHICH WILL EXIST ACROSS  SRN WI INTO SWRN LOWER MI AROUND 00Z. ALTHOUGH NOT PARTICULARLY  MOIST...COOLING ALOFT WITH THE UPPER TROUGH AND AMPLE LIFT SHOULD  RESULT IN ISOLATED TO SCATTERED SEVERE THUNDERSTORMS MAINLY TUE  AFTERNOON AND EVENING.     ..ERN IA...IL...IND...WRN OH...SRN WI AND SRN LOWER MI...NRN KY    ISOLATED ELEVATED STORMS CAPABLE OF MARGINALLY SEVERE HAIL WILL BE  POSSIBLE TUE MORNING FROM CNTRL IA INTO WRN IL ASSOCIATED WITH WARM  ADVECTION WITH AN INCREASING SLY LOW-LEVEL JET. IN THE WAKE OF THIS  ACTIVITY...DESTABILIZATION WILL ENSUE AHEAD OF THE SFC LOW WITH LIFT  INCREASING DURING THE AFTERNOON ACROSS ERN IA...SRN WI...AND NRN IL.  THIS AREA WILL EXPERIENCE HEIGHT FALLS AND COOLING ALOFT...AS WELL  AS INCREASED SFC CONVERGENCE FAVORABLY TIMED DURING PEAK HEATING.  VEERING AND INCREASING WINDS WITH HEIGHT WILL STRONGLY FAVOR  SUPERCELLULAR STORM MODE. THIS...ALONG WITH STEEP LAPSE RATES  ALOFT...WILL STRONGLY FAVOR LARGE HAIL. HAIL TO THE SIZE OF GOLF  BALLS APPEARS LIKELY...POSSIBLY LARGER DEPENDING ON ACTUAL MOISTURE  LEVELS.     IN ADDITION TO HAIL...AN ISOLATED TORNADO OR TWO CANNOT BE RULED OUT  OVER FAR ERN IA...NRN IL AND FAR SRN WI...ON THE EDGE OF THE  LOW-LEVEL LAPSE RATE PLUME...AND ALSO ALONG THE WARM FRONT WHICH  WILL EXIST ACROSS FAR SRN WI/NRN IL. HERE...LOW-LEVEL HODOGRAPH  CURVATURE WILL BE MAXIMIZED. MAIN MITIGATING FACTOR TO TORNADO  THREAT WILL AGAIN BE MOISTURE LEVELS. THE HAIL THREAT SHOULD PERSIST  AS THE LOBE OF ASCENT EJECTS NEWD INTO SRN LOWER MI AND WRN  OH...ALBEIT WITH DWINDLING INSTABILITY.    ELSEWHERE...THUNDERSTORM COVERAGE IS EXPECTED TO BE LIMITED  GENERALLY S OF THE OH RIVER...OR S OF THE MIDLEVEL SPEED MAX WHERE A  STRONG TEMPERATURE GRADIENT WILL EXIST. BOTH RAPIDLY VEERING WINDS  IN THE LOWER LEVELS AND DRY AIR ALOFT SHOULD LIMIT STORM COVERAGE  WITH SRN EXTENT.    ..JEWELL.. 03/14/2016  

[Indystorm]

No enhanced area as of yet.  That might change come Tuesday morning as mesoscale influences become better known.

[Geos]

there is clearly a low threat for low-end severe weather along the lake but it's hardly worth talking about considering excellent tornado chances further west

 

Definitely better west.

The temperature contrast between here and say De Kalb will be quite extreme. 0z on the 4km there's low 40s along the lake and low 60s to the southwest.

[Stebo]

No enhanced area as of yet.  That might change come Tuesday morning as mesoscale influences become better known.

Yeah not to mention they are still riding the lowest model for dew points still, making no mention of the 60+ dew points.

[Hoosier]

Taking a look at where the 60 degree dewpoints are currently, you basically have to go down to about 100 miles from the Gulf coast. 

[nwburbschaser]

Yeah not to mention they are still riding the lowest model for dew points still, making no mention of the 60+ dew points.

I'm still in the camp of not buying into the higher dews on the NAM. 

[rolltide_130]

Yeah not to mention they are still riding the lowest model for dew points still, making no mention of the 60+ dew points.

 

FWIW, I agree with their stance on the low DP's. The NAM's projected DP's across AR failed to verify yesterday, and as a result the event, while not a total bust, did not live up to expectations and the 10% hatched risk area failed to verify. The NAM was the outlier with the DP's on that event and overestimated, and I expect the same thing to happen here unless the other models start getting on board.