Possible Severe Weather May 11

[GCANE]

GFS and EURO both showing a digging UL trough coming into the West Coast and moving east.

A deep surface low could phase with it advecting GOM moisture into the Plains.

By the looks of it at this point, could go negative tilt as it swings into the Plains and pushes east.

Stay tuned.


PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
430 AM EDT TUE MAY 03 2011

VALID 12Z SAT MAY 07 2011 - 12Z TUE MAY 10 2011


THE CLOSED CIRCULATION OVER THE NORTHEAST ON DAY 3 IS FCST TO LIFT
NORTHWARD INTO EASTERN CANADA AS VARIOUS WEAKER IMPULSES UNDERCUT
THE SYSTEM FROM THE MIDWEST EASTWARD. HEIGHTS ARE FCST TO RISE
SUBSTANTIALLY OVER THE ERN HALF OF THE NATION AFTER DAY 5. IN THE
WEST...00Z MODELS AND ENS MEAN SOLNS ARE IN REASONABLE AGREEMENT
IN SUPPORTING A STRONG TROUGH AMPLIFYING ACROSS THE INTERIOR WEST
AFTER DAY 5. THE ECMWF AND CMC MODELS INDICATE THAT THE WRN
TROUGH WILL DIG INTO THE SOUTHWEST...WHILE THE GFS AND GEFS MEAN
OFFER MORE PROGRESSIVE SOLNS. LARGELY FOLLOWED THE ECMWF/CMC SFC
PATTERN. THIS SHOULD RESULT IN THE FORMATION OF A DEEP AND SLOW
MOVING LOW LEVEL CIRCULATION OVER THE CENTRAL PLAINS ON DAYS 6-7.

HEDGE

[GCANE]

Very strong moisture feed into the system.

[KatDaddy]

Joe B is expecting another large severe weather event as a trough develops in the W next week with abundant moisture and warm inadvance of it.

[srainhoutx]

May need to back the date up by a day. SPC suggests from Sunday onward. The trend of a deep, slow moving Western trough would suggest another substantial threat may well be ahead, IMO.

[fogbreath]

Are we looking at something similar regionally (not necessarily in intensity - that would be hard to match) to last week's storm?

I ask only in that I get to fly out from the generally calm climes of Northern California into Central Ohio during this timeframe

[RL3AO]

Still early but it looks like more of a Central/Northern Plains and into the midwest.

[CrazyC83]

Looks like I will be in a holding pattern next Wednesday, most likely in Nashville, Tennessee. What is the early timing estimate for the I-65 and I-75 corridors?

[GCANE]

Just what the MS watershed needs - more heavy rain over a 3 day period.

At this point FIM has Wed for Midwest I-75, I-65.

[srainhoutx]

SPC in 4-8 day outlook:

SEVERE AREAS BEGINNING SUN/MAY 8TH AND LASTING THROUGH ABOUT MAY
10TH ARE LIKELY FORTHCOMING FOR MUCH OF THE CNTRL U.S. AS THE EVENT
NEARS AND PREDICTABILITY INCREASES.


Maybe a title edit is in order, GCANE.

[GCANE]

SPC in 4-8 day outlook:

SEVERE AREAS BEGINNING SUN/MAY 8TH AND LASTING THROUGH ABOUT MAY
10TH ARE LIKELY FORTHCOMING FOR MUCH OF THE CNTRL U.S. AS THE EVENT
NEARS AND PREDICTABILITY INCREASES.


Maybe a title edit is in order, GCANE.

Done - thanks.

I also was looking at the models this morning and it seems that some blocking in the mid Atlantic is setting up along with the block between Greenland and UK.

Will be interesting how that interacts with this system early next week.

[GCANE]

[GCANE]

The end of the current SREF run is showing moderate to severe thunderstorms for OK and AR Saturday afternoon.

[GCANE]

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 050900
SPC AC 050900

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0400 AM CDT THU MAY 05 2011

VALID 081200Z - 131200Z

...DISCUSSION...
FORECAST MODELS AND VARIOUS ENSEMBLE MEMBERS ARE IN RELATIVELY GOOD
AGREEMENT THROUGH SUN/D4 IN DIGGING A STRONG UPPER TROUGH ACROSS THE
WRN STATES...AND MOVING AN UPPER LEVEL RIDGE AXIS FROM THE CNTRL
PLAINS EWD TO THE MS RIVER BY 00Z MON. AS THIS OCCURS...LOW PRESSURE
WILL DEEPEN OVER THE CNTRL HIGH PLAINS...AND SLY SURFACE FLOW WILL
BRING MID TO UPPER 60S F BOUNDARY LAYER DEWPOINTS INTO OK AND SRN KS
E OF A DRYLINE. STRONG HEATING AND MIXING W OF THE DRYLINE BENEATH
WSWLY MID LEVEL FLOW OF 30-40 KTS AND A VERY STEEP LAPSE RATE
PROFILE SHOULD BE FAVORABLE FOR SUPERCELLS CAPABLE OF VERY LARGE
HAIL...GUSTY OUTFLOW WINDS AND PERHAPS A FEW TORNADOES...ALTHOUGH
T/TD SPREADS MAY BE TOO HIGH FOR A SIGNIFICANT TORNADO THREAT.
ALTHOUGH LOW LEVEL MOISTURE QUALITY WILL BE GREATER WITH EWD
EXTENT...CAPPING WILL BE A PROBLEM. STORM MOTIONS SHOULD BE
SLOW...SO EXPECT STORMS TO AFFECT A RELATIVELY CONCENTRATED AREA
BEFORE DYING BY LATE EVENING.

ON MON/D5...MODELS REMAIN IN GOOD AGREEMENT WITH THE UPPER AIR
PATTERN AS THE TROUGH SINKS SWD ACROSS THE GREAT BASIN. LOW PRESSURE
WILL AGAIN DEEPEN OVER THE CNTRL HIGH PLAINS WITH SLY SURFACE FLOW
PERSISTING. WITH MOISTURE IN PLACE...IT APPEARS MORE DRYLINE STORMS
WILL OCCUR...SIMILAR TO THE PREVIOUS DAY.

BY TUE/D6 INTO WED/D7...FLOW OVER THE PLAINS WILL BECOME
INCREASINGLY MERIDIONAL AS THE UPPER TROUGH BOTTOMS AND BEGINS
MOVING EWD. ALSO AT THIS TIME...A SUBTROPICAL JET IS EXPECTED TO
MOVE NWD AND PHASE WITH THE MAIN TROUGH...INCREASING UPPER LEVEL
WIND PROFILES. ALL THE WHILE...A DRYLINE WILL REMAIN ACROSS THE
CNTRL/SRN PLAINS WITH STRONG INSTABILITY AND AMPLE VEERING SHEAR
PROFILES FOR SUPERCELLS EACH DAY. TUE AND WED APPEAR TO HAVE A
GREATER TORNADO THREAT THAN ON SUN/MON WITH HIGHER THETA-E AIR AND
BETTER HODOGRAPHS. AN ISOLATED STRONG TORNADO MAY OCCUR...ESPECIALLY
ON TUE WHEN A STRONG NOCTURNAL LOW LEVEL JET RESPONSE IS FORECAST TO
OCCUR DURING THE EVENING.

GIVEN SOME SUBSTANTIAL DIFFERENCES WITH THE TROUGH ON D7...WILL
DEFER ON ADDING ANY ADDITIONAL AREAS.

..JEWELL.. 05/05/2011

[GCANE]

Stationary dryline from Sunday thru Wednesday TX & OK.

Height falls Iowa and N IL look impressive Tuesday & Wednesday.

Chicago needs to keep an eye on this.

[GCANE]

Keep an eye on the models on what they are forecasting for mid next week.

A strong mid-level low looks to be creeping in from off the coast of BC.

[GCANE]

GFS showing PV cuts off 150 hrs out and looks well defined to about the 320K level.

[GCANE]

Looks like capping will hold back storms Sunday and Monday.

Chances look better for severe weather Tuesday.

Highest threat for severe weather is now Wednesday.






DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0353 AM CDT FRI MAY 06 2011

VALID 091200Z - 141200Z

...DISCUSSION...
UPPER FLOW WILL BECOME MORE MERIDIONAL ACROSS THE COUNTRY IN THE
MEDIUM RANGE AS THE WEST COAST TROUGH DEEPENS AND THEN BEGINS TO
EJECT ENE INTO THE PLAINS BY TUE AND WED. AS THE TROUGH DIGS INTO
THE GREAT BASIN...SWLY LOW/MID-LEVEL FLOW WILL TRANSPORT A VERY
STRONG EML ACROSS THE PLAINS FROM THE MEXICAN PLATEAU. AT THE SAME
TIME...THERE WILL BE IMPROVING LOW-LEVEL GULF MOISTURE ACROSS THE
PLAINS...PARTICULARLY TUESDAY AND WEDNESDAY.

DRYLINE TSTM INITIATION IS COMPARATIVELY MORE UNCERTAIN ON MONDAY
AFTN THAN ON SUNDAY AS MID-LEVELS FURTHER WARM IN ADVANCE OF THE
DIGGING IMPULSE INTO THE DESERT SW. MORE ROBUST SEVERE EVENTS
APPEAR LIKELY ON TUESDAY AND...PARTICULARILY...ON WEDNESDAY /DAY 5
AND 6/ AS THE UPPER STORM SYSTEM BODILY MOVES ONTO THE PLAINS.
THESE STORMS WILL DEVELOP IN INCREASINGLY LARGE HODOGRAPHS AND
BUOYANCY...YIELDING THREATS FOR VERY LARGE HAIL...TORNADOES AND
DAMAGING WIND GUSTS.

BEYOND DAY 6...MEDIUM RANGE GUIDANCE INTRODUCES A INCREASING SPREAD
ON THE HANDLING OF THE TROUGH AS IT TRANSLATES EWD ACROSS THE
MIDWEST AND NERN STATES. THIS RENDERS THE REMAINDER OF THE MEDIUM
RANGE PREDICTABILITY TOO LOW TO DELINEATE SVR WEATHER AREAS.

..RACY.. 05/06/2011

[GCANE]

GFS is spinning up a Texas Hooker Wednesday.

This is starting to look like the same setup as last week's outbreak.

[monicaei]

Can anyone tell me in lay mans terms exactly how much additional rain is expected from this? I'm in south LA and there are real concerns about the River. I'm pretty sure the crest forecast is based only on the river as of now, and doesn't include the possibility of additional rain up stream.

[GCANE]

Can anyone tell me in lay mans terms exactly how much additional rain is expected from this? I'm in south LA and there are real concerns about the River. I'm pretty sure the crest forecast is based only on the river as of now, and doesn't include the possibility of additional rain up stream.

I think around Monday may have a better idea as the short-term and medium-term models come into range such as HRRR, SREF, and NAM.