April 2nd - April 5th Severe Weather

[Hoosier]

Definitely sounds far fetched, but the NAM forecasts winds at 850mb between 70-80kts over a wide swath for much of tomorrow morning. My gut feeling is it's overdone on the moisture return, but I think we'll see dews eventually make it up close to 60 by early evening.

That really strong low level flow should help. We don't have the evapotranspiration that we do in the summer so that is a negative.

[weathergy]

Here's to hoping the MCS holds together for SEMI Sunday night. More than likely won't happen though.

[Indystorm]

Dew is already 58 at OKC at this hour with a south wind at 18, gusting to 24. We do have an interesting scenario of how fast quality moisture can return northward given drought conditions presently existing in the central and southern plains. My hunch is that the moisture will make it up the delta as Beau alluded to in his post and the dry air will push the dry line/eml farther east than usual, which is the set up that has been progged for these spring events in this waning Nina.

[Thundersnow12]

dew points in parts of OK have went up anywhere from 11-17 degrees since 18z.

[Indystorm]

And GFS progs a 130-150 knot 300 mb jet over IN and MI on Monday evening. I'm concerned for what Monday may bring to central KY and TN.

[PatrickSumner]

And GFS progs a 130-150 knot 300 mb jet over IN and MI on Monday evening. I'm concerned for what Monday may bring to central KY and TN.

I would leave Indiana out of this either....

[cyclone77]

The HRRR shows 60 degree dews already crossing into southern Iowa at noon tomorrow.

[Ed Lizard]

I see incredible amounts of instability and shear going untapped tomorrow afternoon/evening Kansas and Southward, looking at forecast soundings.

[Ed Lizard]

Anyone with some knowledge have a favorite as far as model families go as far as SREF members?

The RSM members, all the perturbations, looking at the 2100 off the PSU e-Wall, all have a more super-cell look on Monday than the other model families.

Edit to Add: Google not a big help, this seems more a personal experience thing...

http://www.google.com/#sclient=psy&hl=en&rlz=1R2ADRA_enUS421&q=regional+spectral+model&aq=0&aqi=g1g-v2g-b2&aql=f&oq=regional+spectr&pbx=1&rlz=1R2ADRA_enUS421&bav=on.2,or.r_gc.r_pw.&fp=a9acdcd2312857c2

[upsloper]

Was looking at the University of Illinois WRF ensemble. 3/7 available members mix out low-level moisture Sunday over the area of interest, 2 rather extremely with sub-1000m LCLs only to be found in a small area hugging the low center at 00Z.

[baroclinic_instability]

Anyone with some knowledge have a favorite as far as model families go as far as SREF members?

The RSM members, all the perturbations, looking at the 2100 off the PSU e-Wall, all have a more super-cell look on Monday than the other model families.

Edit to Add: Google not a big help, this seems more a personal experience thing...

http://www.google.co...9acdcd2312857c2

The "cell" look is actually convective qpf bullseye blobs. It is essentially the old GFS (Regional Spectral Model) with far less aggressive filtering. It is a junky model--probably the worst of the SREF bunch although the old ETA is close.

[Ed Lizard]

The "cell" look is actually convective qpf bullseye blobs. It is essentially the old GFS (Regional Spectral Model) with far less aggressive filtering. It is a junky model--probably the worst of the SREF bunch although the old ETA is close.

Oh. The blobs look like what isolated cells would tend to make in a 3 hour period.

I don't know verification scores or anything, but if an entire family of the SREF is inferior, I'd think removing it, maybe adding additional perturbations of the better short range models would be the way to go.

[baroclinic_instability]

Oh. The blobs look like what isolated cells would tend to make in a 3 hour period.

I don't know verification scores or anything, but if an entire family of the SREF is inferior, I'd think removing it, maybe adding additional perturbations of the better short range models would be the way to go.

What you are seeing are the old sub-grid scale QPF "blobs" of old that plagued the old GFS. It was so bad there is a whole page dedicated to it. http://www.hpc.ncep.noaa.gov/qpfbombs/

Since the upgrade this summer--this has been toned down significantly in the GFS--unfortunately the RSM still sucks. From what I have heard the ETA/RSM are going to be dumped soon.

[Ed Lizard]

What you are seeing are the old sub-grid scale QPF "blobs" of old that plagued the old GFS. It was so bad there is a whole page dedicated to it. http://www.hpc.ncep.noaa.gov/qpfbombs/

Since the upgrade this summer--this has been toned down significantly in the GFS--unfortunately the RSM still sucks. From what I have heard the ETA/RSM are going to be dumped soon.

But that suggests the QPF bombs are from inability to handle instabilty over a coarse grid, and notes the regional models can suffer from this but are less likely t because of finer grid, and I assume the RSM is finer grid.

[baroclinic_instability]

But that suggests the QPF bombs are from inability to handle instabilty over a coarse grid, and notes the regional models can suffer from this but are less likely t because of finer grid, and I assume the RSM is finer grid.

No it is not. In fact it is coarser than the new GFS.

Trust me it is a worthless model. It produces those awful blobs all year long including in the winter.

[Stebo]

Day 1 Mod out with 10% tornado non hatched

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1258 AM CDT SUN APR 03 2011

VALID 031200Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF ERN KS AND NW

MO...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID-MO

VALLEY...CNTRL PLAINS...SRN PLAINS...WRN OZARKS AND WRN GREAT

LAKES...

...SEVERE WEATHER EVENT EXPECTED FROM ERN KS NEWD ACROSS NRN MO INTO

WRN AND NRN IL THIS AFTERNOON AND EVENING...

...MID-MO VALLEY/CNTRL PLAINS/MID-MS VALLEY/WRN GREAT LAKES...

AN UPPER-LEVEL TROUGH WILL MOVE INTO THE NRN PLAINS AND CNTRL

ROCKIES TODAY. WELL AHEAD OF THE SYSTEM...A POWERFUL 65 TO 80 KT

LOW-LEVEL JET WILL BE IN PLACE ACROSS THE MID-MO VALLEY AND LOWER OH

VALLEY THIS AFTERNOON. THE LOW-LEVEL JET WILL RAPIDLY TRANSPORT

MOISTURE NEWD INTO THE SLIGHT RISK AREA BY MID-AFTERNOON WITH SFC

DEWPOINTS LIKELY REACHING INTO THE MID 60S F FROM ERN KS NEWD TO WRN

IL. THE MOIST AIRMASS SHOULD ALLOW MODERATE INSTABILITY TO DEVELOP

ACROSS A BROAD AREA AHEAD OF A FAST-MOVING COLD FRONT. AS THE

CAPPING INVERSION WEAKENS AND LOW-LEVEL CONVERGENCE INCREASES ALONG

THE FRONT...NUMEROUS STRONG TO SEVERE THUNDERSTORMS SHOULD INITIATE

WITH A BROKEN LINE DEVELOPING DURING THE LATE AFTERNOON.

FORECAST SOUNDINGS AT 21Z SUGGEST THE STRONGEST INSTABILITY WILL BE

LOCATED IN ERN KS AND WRN MO WHERE MLCAPE VALUES ARE FORECAST TO

REACH THE 2500 TO 3500 J/KG RANGE. IN ADDITION...A PLUME OF STEEP

MID-LEVEL LAPSE RATES IS FORECAST TO NOSE INTO ERN KS AND NW MO

WHERE DEEP LAYER SHEAR SHOULD BE QUITE STRONG. THIS ENVIRONMENT WILL

LIKELY SUPPORT SUPERCELL DEVELOPMENT WITH A WIDESPREAD THREAT FOR

LARGE HAIL ESPECIALLY ACROSS ERN KS AND NW MO WHERE A MODERATE RISK

AREA HAS BEEN OUTLOOKED. VERY LARGE HAIL WILL BE POSSIBLE WITH THE

MORE DOMINATE SUPERCELLS THAT REMAIN DISCRETE. TORNADOES WILL ALSO

BE POSSIBLE WITH THE BETTER-ORGANIZED SUPERCELLS. THE TORNADO THREAT

MAY BE GREATEST NEWD ACROSS NRN MO INTO WRN AND NRN IL WHERE THE

STORMS WILL HAVE ACCESS TO GREATER LOW-LEVEL SHEAR. IF DISCRETE

ROTATING STORMS CAN PERSIST INTO THE EARLY EVENING WHEN THE

LOW-LEVEL JET IS FORECAST TO STRENGTHEN...THEN AN ISOLATED STRONG

TORNADO WILL BE POSSIBLE. DUE TO THE STRONG LOW-LEVEL FLOW OF 60 TO

70 KT AND BECAUSE OF THE AMOUNT OF INSTABILITY FORECAST...WIND

DAMAGE COULD BE WIDESPREAD FROM ERN KS NEWD ACROSS NRN MO INTO NW IL

ESPECIALLY IF A NEARLY CONTINUOUS LINE OF INTENSE STORMS DEVELOPS

DURING THE EARLY EVENING.

...SRN PLAINS/WRN OZARKS...

MOISTENING OF THE AIRMASS ACROSS THE SRN PLAINS WILL CONTINUE TODAY

AS THE SRN END OF A WELL-DEFINED LOW-LEVEL JET MOVES EWD ACROSS THE

REGION. MODERATE INSTABILITY IS FORECAST BY MID TO LATE AFTERNOON

FROM CNTRL AND NORTH TX EXTENDING NWD INTO CNTRL AND ERN OK WHERE

FORECAST SOUNDINGS SHOW MLCAPE VALUES AROUND 2500 J/KG. IN SPITE OF

THE INSTABILITY...A CAPPING INVERSION WILL LIKELY REMAIN IN PLACE

FOR MUCH OF THE AFTERNOON AND EVENING SUPPRESSING CONVECTIVE

DEVELOPMENT. SEVERAL MODEL FORECASTS INITIATE STORMS IN NE OK AND NW

AR DURING THE LATE EVENING WITH STORMS EXPANDING SWWD ALONG A COLD

FRONT DURING THE OVERNIGHT PERIOD. THE MODERATE INSTABILITY...STEEP

MID-LEVEL LAPSE RATES AND STRONG DEEP LAYER SHEAR SHOULD BE

SUFFICIENT FOR A LARGE HAIL AND WIND DAMAGE THREAT. AFTER

MIDNIGHT...ISOLATED THUNDERSTORM DEVELOPMENT COULD OCCUR SWWD ACROSS

CNTRL AND NORTH TX AS THE COLD FRONT MOVES INTO THE REGION FROM THE

NORTHWEST. FORECAST SOUNDINGS IN CNTRL AND NORTH TX AT 09Z TO 12Z

SUGGEST DEEP LAYER SHEAR MAY BE STRONG ENOUGH FOR A MARGINAL WIND

DAMAGE AND HAIL THREAT.

[baroclinic_instability]

Oh.

From this winter. Enjoy. It is a junk model.

http://www.americanw...post__p__394744

[Thundersnow12]

I have been waiting all winter for this...not hatched...yet.

THE TORNADO THREAT MAY BE GREATEST NEWD ACROSS NRN MO INTO WRN AND NRN IL WHERE THE STORMS WILL HAVE ACCESS TO GREATER LOW-LEVEL SHEAR. IF DISCRETE ROTATING STORMS CAN PERSIST INTO THE EARLY EVENING WHEN THE LOW-LEVEL JET IS FORECAST TO STRENGTHEN...THEN AN ISOLATED STRONG TORNADO WILL BE POSSIBLE.

[David Reimer]

I have been waiting all winter for this...not hatched...yet.

THE TORNADO THREAT MAY BE GREATEST NEWD ACROSS NRN MO INTO WRN AND NRN IL WHERE THE STORMS WILL HAVE ACCESS TO GREATER LOW-LEVEL SHEAR. IF DISCRETE ROTATING STORMS CAN PERSIST INTO THE EARLY EVENING WHEN THE LOW-LEVEL JET IS FORECAST TO STRENGTHEN...THEN AN ISOLATED STRONG TORNADO WILL BE POSSIBLE.

Since the outlook didn't mention Iowa, it has a good chance of succeeding. I was surprised to see the moderate risk out for Kansas where there is more doubt in the possibility of initiation. Normally I would take that as an increased boost in confidence, but after the past two weeks of cap-busts, I'm rather pessimistic.

[earthlight]

[Stebo]

Since the outlook didn't mention Iowa, it has a good chance of succeeding. I was surprised to see the moderate risk out for Kansas where there is more doubt in the possibility of initiation. Normally I would take that as an increased boost in confidence, but after the past two weeks of cap-busts, I'm rather pessimistic.

Yeah, I can see the concern, but if things do pop they could pop in a big way.

[Thundersnow12]

Hoosier posted this thing when it came hot off the press

We will leaving Plainfield around 10 30am after doing hand analysis.

[thewxmann]

Day 2 is 30% hatched in the lower MS Valley. Heavily weighed towards ECMWF. Mentions tornadoes (though with the H5 wind vector CCW relative to the sfc wind vector at some points in time.....).

[Thundersnow12]

Since the outlook didn't mention Iowa, it has a good chance of succeeding. I was surprised to see the moderate risk out for Kansas where there is more doubt in the possibility of initiation. Normally I would take that as an increased boost in confidence, but after the past two weeks of cap-busts, I'm rather pessimistic.

I'm quite optimistic for up here and if we can get a discrete supercell....could be quite the show on the home turf.

[Stebo]

Hoosier posted this thing when it came hot off the press

We will leaving Plainfield around 10 30am after doing hand analysis.

Where you looking to setup at Galesburg or Macomb? Or further West than that?

[Hoosier]

Hoosier posted this thing when it came hot off the press

We will leaving Plainfield around 10 30am after doing hand analysis.

You probably shouldn't leave Plainfield given their tornado track record...

[Stebo]

You probably shouldn't leave Plainfield given their tornado track record...

Hoosier offers up a nice counterargument

[Thundersnow12]

Where you looking to setup at Galesburg or Macomb? Or further West than that?

Going to try to stay on the IL side so we'll see. I said that on June 5th last year and ended up IA for few hours. Maybe I should do the same thing since I'm very superstitious, drift into IA just south of 80 to Muscatine, head south to Mt. Pleasant on 34 then back east into IL as mother nature goes nuts.

But if I had to pick a target I'd say GBG (which was my target on 6/5) Yates City/Elmwood/Streator/Dwight all under the gun again..

[Stebo]

Going to try to stay on the IL side so we'll see. I said that on June 5th last year and ended up IA for few hours. Maybe I should do the same thing since I'm very superstitious, drift into IA just south of 80 to Muscatine, head south to Mt. Pleasant on 34 then back east into IL as mother nature goes nuts.

But if I had to pick a target I'd say GBG (which was my target on 6/5) Yates City/Elmwood/Streator/Dwight all under the gun again..

Yeah that looks like a good spot, of course you can adjust on the fly if need be, but Galesburg is a good flex point.

[Stebo]

GRR's thoughts

THUNDER DOES NOT LOOK LIKELY UNTIL LATER THIS AFTERNOON WHEN THE LLJ

WILL BECOME FOCUSED ON THE AREA AND ENOUGH INSTABILITY MOVES

IN/DEVELOPS ACROSS THE AREA. THIS LLJ NOSING IN WILL KEEP PCPN

ONGOING ACROSS THE AREA THROUGH THE AFTERNOON AND INTO THE EVENING

HOURS. THE BEST CHANCE OF THUNDER WILL COME FROM MID EVENING AND

INTO THE PRE-DAWN HOURS ON MON. THIS IS WHEN THE TRIPLE POINT IS

EXPECTED TO TRAVERSE THE AREA ALONG A LINE ROUGHLY FROM HOLLAND TO

ALMA. THIS IS EXPECTED TO PUT THE SRN PORTION OF THE AREA INTO THE

WARM SECTOR.

WE EXPECT TEMPS TO RISE INTO THE 50S AND APPROACHING 60 DOWN

SOUTH THROUGH ABOUT 06Z OR SO AS THE WARM SECTOR MOVES IN. THIS WILL

OBVIOUSLY BE THE TIME WHEN THE BEST INSTABILITY MOVES ACROSS THE

AREA. ELEVATED INSTABILITY IS PRESENT WHERE 925 BASED LI/S FALL DOWN

TO -4 OR SO. MODELS INDICATE SOME SFC BASED INSTABILITY WILL BE

POSSIBLE...HOWEVER THE TIME OF DAY THE WARM SECTOR MOVES THROUGH

WILL BE A NEGATIVE FOR SIGNIFICANT SFC BASED INSTABILITY WITHOUT ANY

SOLAR RADIATION.

IT APPEARS THAT THE NIGHT TIME ARRIVAL OF THE WARM SECTOR AND

RESULTING LACK OF SFC BASED INSTABILITY WILL BE THE BIGGEST FACTOR

NEGATING SEVERE WX POTENTIAL FOR SW LOWER AS THE CONVECTION ALONG

THE COLD FRONT MOVES IN. DEEP LAYER WIND SHEAR IS ON THE ORDER OF

50+ KNOTS...AND 0-1KM SHEAR IS OVER 40 KNOTS WHICH WOULD SUPPORT

ORGANIZED STORMS IF THERE WAS SUFFICIENT INSTABILITY. THE HODOGRAPHS

AND LOW LCL HEIGHTS ARE QUITE FAVORABLE FOR TORNADO DEVELOPMENT NEAR

THE TRIPLE POINT. HOWEVER ONCE AGAIN...THE LACK OF SFC BASED

INSTABILITY WILL LIKELY KEEP THE THREAT RATHER LIMITED. EVEN LARGE

HAIL POTENTIAL IS LIMITED AS CAPE PROFILES ARE RATHER THIN.

DTX's thoughts

DYNAMIC LOW PRESSURE SYSTEM IS FORECAST TO TRACK NORTHEAST INTO

CENTRAL LOWER MICHIGAN OVERNIGHT BEFORE THE SYSTEM OCCLUDES AND THE

SURFACE LOW LIFTS NORTHEAST INTO ONTARIO ON MONDAY. A 60+ KNOT LOW

LEVEL JET WILL FORCE THE 925-850MB WARM FRONT NORTH TO LAKE HURON

WITH ANOTHER SURGE OF THETA-E ADVECTION BRINGING SHOWERS AND

THUNDERSTORMS OVERNIGHT INTO MONDAY MORNING. THE AIRMASS WILL

UNDERGO CONSIDERABLE MOISTENING AS PW VALUES CLIMB TO 1.30 INCHES

WITH 850MB DEWPOINTS NEAR 12C AND SURFACE DEWPOINTS REACHING THE

UPPER 50S IN THE EXTREME SOUTH. CONVECTION ON SUNDAY NIGHT WILL BE

SOMEWHAT ORGANIZED WITH TREMENDOUS SHEAR ALONG BOTH THE WARM FRONT

AND APPROACHING COLD FRONT AND SHOWALTER INDICES OF -2 TO -5C. MODEL

SOUNDINGS INDICATE THUNDERSTORM ACTIVITY SHOULD REMAIN ELEVATED BUT

WILL BE SOMETHING TO KEEP AN EYE ON AS WARMER AIR SNEAKS INTO

EXTREME SOUTHERN LOWER MICHIGAN. THE COUPLED UPPER LEVEL JET

OVERHEAD MAY PLAY A ROLE IN PULLING THE SURFACE LOW FURTHER TO THE

NORTH AND WEST(AS SUGGESTED BY THE GFS/UKMET) BUT MAY ALSO RESULT IN

A FASTER OCCLUSION WITH THE WARM LOW LEVEL AIR BEING PINCHED OFF.

THE ARRIVAL OF THE WARM FRONT WILL STILL LIKELY NOT BE ENOUGH FOR

CONVECTION TO BECOME SURFACE BASED GIVEN THE VERY WARM AIR SURGING

NORTH ALOFT. WITH THAT SAID...TEMPERATURES WILL RISE OVERNIGHT WITH

LOCATIONS FROM DETROIT SOUTH MAKING A RUN AT 60 DEGREES WHILE THE

SAGINAW VALLEY/NORTHERN THUMB REGIONS IS STUCK IN THE MID 40S. THERE

WILL BE A GOOD CHANCE OF SMALL HAIL AND BRIEF HEAVY RAINFALL WITH

THUNDERSTORMS OVERNIGHT. THERE IS EVEN AN ISOLATED RISK OF A SEVERE

STORM WITH HAIL TO ONE INCH IN DIAMETER. LOCALIZED FLOODING MAY ALSO

BE A THREAT IF STORMS END UP TRAINING ALONG THE WARM FRONT IN THIS

MOISTURE RICH ENVIRONMENT.