Return of significant severe weather? June 18-21

[CrazyC83]

The SPC seems to think so. Late spring/early summer outbreaks are not uncommon, especially in the northern Plains, Great Lakes and Northeast. Models disagree on the strength of the shear though.

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 130901
SPC AC 130901

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0401 AM CDT MON JUN 13 2011

VALID 161200Z - 211200Z

...DISCUSSION...
13/00Z GFS/ECMWF GUIDANCE EAST OF THE MS RIVER DIFFERS WITH THE
EVOLUTION AND EWD PROGRESSION OF THE DAY 3 UPPER MS VALLEY/WRN GREAT
LAKES CLOSED LOW. MEANWHILE...THE GFS/ECMWF GENERALLY AGREE IN THE
LARGE PATTERN IN THE WEST WITH A TROUGH EVOLVING ACROSS THIS REGION
AND HEIGHTS RISING FROM THE SRN PLAINS THROUGH THE UPPER MS VALLEY
INTO ONTARIO.

THE POTENTIAL EXISTS FOR PERIODIC SEVERE THREATS OVER THE NRN
PLAINS...AND AT TIMES THE CENTRAL PLAINS...AS SHORT WAVE TROUGHS
MOVE NEWD ACROSS THE REGION. A THREAT FOR ORGANIZED STORMS IS
POSSIBLE ON DAY 6 /SAT JUN 18/ OVER THE NRN PLAINS AND INTO THE
UPPER MS VALLEY ON DAY 7 /SUN JUN 19/. HOWEVER...MODELS DIFFER IN
THE STRENGTH OF THE SHORTWAVE TROUGH SUPPORTING THIS THREAT...AND
THUS PRECLUDE THE INCLUSION OF A SEVERE WEATHER THREAT AREA OVER
THESE AREAS DAY 6/7. ALTHOUGH THE 00Z GFS/ECMWF AGREE WITH A STRONG
SHORTWAVE TROUGH EJECTING NEWD ACROSS THE NRN/CENTRAL PLAINS ON DAY
8 /MON JUN 20/...INTRA-MODEL SPREAD IN THE GFS AND ECMWF PRECLUDES
AN INCLUSION OF A SEVERE WEATHER THREAT AREA THIS LATE IN THE
FORECAST PERIOD.

..PETERS.. 06/13/2011

CLICK TO GET WUUS48 PTSD48 PRODUCT

[CrazyC83]

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 150858
SPC AC 150858

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0358 AM CDT WED JUN 15 2011

VALID 181200Z - 231200Z

...DISCUSSION...
MODELS SUGGEST A POTENTIAL FOR SEVERE STORMS ACROSS PARTS OF THE
CENTRAL INTO NRN PLAINS ON DAY 4 /SAT JUN 18/. HOWEVER...GREATER
AGREEMENT EXISTS ON DAY 5 FOR A MORE PRONOUNCED SHORTWAVE TROUGH
MOVING THROUGH THE GREAT BASIN/FOUR CORNERS REGION ON DAY 4 TO TRACK
ACROSS THE CENTRAL PLAINS TO UPPER MS VALLEY ON DAY 5 /SUN JUN 19/.
MODERATE-VERY STRONG INSTABILITY /MUCAPE 2000-4000 J PER KG/ IS
EXPECTED FROM ERN NEB/IA TO THE ERN DAKOTAS/MN...WITH INCREASING
DEEP LAYER SHEAR OF 35-50 KT AS A 50+ KT SWLY MIDLEVEL JET REACHES
NEB TO MN BY PEAK HEATING ON SUNDAY. GIVEN MODEL AGREEMENT...THESE
FACTORS SUPPORT A REGIONAL SEVERE WEATHER THREAT FROM THE MID MO
VALLEY TO ERN DAKOTAS/MN.

BEYOND DAY 5...THE 15/00Z GFS INDICATES A THREAT FOR SEVERE STORMS
ACROSS THE UPPER MS TO LOWER MO VALLEYS ON DAY 6 /MON JUN 20/...
WHILE THE 15/00Z ECMWF SUGGESTS THIS SAME REGION AND SWWD INTO ERN
KS TO OK FOR DAY 7 /TUE JUN 21/. GIVEN THE TIMING DIFFERENCES IN
THE MODELS WITH THE ENEWD EJECTION OF THE WRN TROUGH INTO THE NORTH
CENTRAL STATES...A REGIONAL SEVERE WEATHER AREA WILL NOT BE INCLUDED
FOR THE LATTER PART OF THE MEDIUM RANGE OUTLOOK.

..PETERS.. 06/15/2011

CLICK TO GET WUUS48 PTSD48 PRODUCT

[CrazyC83]

This seems to have a multi-day outbreak setup. There is an omega block ridge sitting over northern Ontario and likely isn't going anywhere anytime soon.

[Dave]

Looks like the OH valley comes into play again. June is one of our highest risk months for severe weather here in southern Indiana and this year isn't any different so far. Normally by the first of July our we move into a hot/dry period which will last through August. See if it holds true again for the summer of 2011.

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0240 AM CDT THU JUN 16 2011

VALID 181200Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS EXTENDING FROM THE NRN AND
CENTRAL HIGH PLAINS EWD THROUGH THE MID MS/OH VALLEYS TO THE LOWER
GREAT LAKES AND PA...

...SYNOPSIS...
A BLOCKING PATTERN EXTENDING FROM THE NWRN STATES AND ACROSS CANADA
WILL PERSIST INTO DAY 3 /SAT/. THE CLOSED LOW OVER ERN CANADA WILL
SHIFT SSEWD ACROSS QUEBEC TOWARD NRN NEW ENGLAND. MEANWHILE...IN
THE WEST A CLOSED LOW WILL RETROGRADE NWWD ACROSS SASKATCHEWAN/
ALBERTA AS A TROUGH DIGS SEWD ACROSS THE PACIFIC NW TO THE GREAT
BASIN...MAINTAINING THE LONGWAVE TROUGH OVER THE WRN STATES. WITH
MORE OF A FLAT RIDGE EXPECTED ACROSS THE SRN HALF OF THE CONUS BY
SATURDAY...MID-UPPER LEVEL FLOW FROM THE SWRN STATES TO THE OH
VALLEY AND MID-ATLANTIC STATES SHOULD BECOME GENERALLY WSWLY.

AT 12Z SATURDAY...MODELS ARE IN GENERAL AGREEMENT INDICATING A WARM
FRONT EXTENDING WNWWD FROM OH TO AN AREA OF LOW PRESSURE LOCATED
OVER ERN IA/NRN IL. A COLD FRONT SHOULD BE TRAILING SWWD FROM THE
LOW THROUGH ERN KS TO THE SRN HIGH PLAINS. THE SURFACE LOW SHOULD
MOVE EWD THROUGH THE OH VALLEY/SRN GREAT LAKES REGION WITH THE COLD
FRONT ADVANCING SLOWLY SEWD INTO THE OH AND MID MS VALLEYS.
MEANWHILE...THE WARM FRONT WILL MOVE EWD REACHING THE LOWER GREAT
LAKES TO MID-ATLANTIC STATES BY 12Z SUNDAY.

...LOWER MO/MID MS VALLEYS TO OH VALLEY/SRN GREAT LAKES...
[SWLY LOW LEVEL WINDS ACROSS THE WARM SECTOR AND BENEATH A PLUME OF
STEEP MIDLEVEL LAPSE RATES SPREADING THROUGHOUT MUCH OF THIS REGION
WILL SUPPORT THE DEVELOPMENT OF MODERATE-VERY STRONG INSTABILITY
FROM THE UPPER OH VALLEY WSWWD TO KS/OK. THE STRONGEST INSTABILITY
SHOULD RESIDE FROM THE MID MS VALLEY INTO ERN KS/NERN OK WITH MLCAPE
OF 2500-3500 J/KG. MODELS SUGGEST SEVERAL MIDLEVEL IMPULSES SHOULD
TRAVERSE THE OH VALLEY/GREAT LAKES ON SATURDAY AIDING IN NEW TSTM
DEVELOPMENT WITHIN THE MOIST/UNSTABLE ENVIRONMENT. EFFECTIVE BULK
SHEAR SHOULD BE GREATEST FROM THE UPPER OH VALLEY INTO PA AND LOWER
GREAT LAKES WHERE ORGANIZED STORMS WILL BE POSSIBLE. ALTHOUGH BULK
SHEAR WILL BE WEAKER WITH WWD EXTENT INTO THE LOWER OH TO LOWER MO
VALLEYS...THE DEGREE OF INSTABILITY AND STEEP LAPSE RATES SUGGEST
SOME STORMS COULD BECOME SEVERE.

...CENTRAL/NRN HIGH PLAINS EWD ACROSS NEB/KS...
DESPITE GENERALLY WEAK LOW LEVEL MOISTURE RETURN INTO THE HIGH
PLAINS OF ERN CO TO SERN MT...STEEP MIDLEVEL LAPSE RATES AND STRONG
SURFACE HEATING ALONG A DEVELOPING LEE TROUGH WILL RESULT IN
MODERATE INSTABILITY /MLCAPE AROUND 1000 J PER KG/. MODELS TEND TO
AGREE WITH THE A MIDLEVEL IMPULSE OR TWO SPREADING NEWD ACROSS THE
CENTRAL/NRN HIGH PLAINS BY 19/00Z PROVIDING FORCING FOR ASCENT FOR
TSTM DEVELOPMENT. EFFECTIVE BULK SHEAR OF 40-50 KT COMBINED WITH
THE STEEP LAPSE RATE ENVIRONMENT SUGGESTS SUPERCELLS WILL BE
POSSIBLE. MODELS SUGGEST STORMS WILL MOVE OFF THE HIGHER TERRAIN
INTO THE WRN DAKOTAS...WITH GREATEST UPSCALE GROWTH INTO AN MCS OR
TWO ACROSS THE CENTRAL PLAINS WHERE INSTABILITY WILL BE STRONGER
INTO SATURDAY NIGHT TO MAINTAIN SOME SEVERE WEATHER THREAT.

[CrazyC83]

This is a very difficult setup with the early spring-like trough blasting right into the summer-like subtropical ridge. June 16, 1992 and June 24, 2003 come to mind.