Convective Hazards - National USData: Map Discussion: Day 1 Day 2 Day 3 Day 4-8

000
ACUS01 KWNS 181259
SWODY1
SPC AC 181257

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0757 AM CDT FRI MAY 18 2012

VALID 181300Z - 191200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
LOOSELY ORGANIZED WRN U.S. TROUGH...WITH NRN MEMBER REPRESENTED BY
CLOSED LOW ON THE BC-AB BORDER AND SRN MEMBER BY TROUGH OVER
NV...WILL CONTINUE EWD THROUGH EARLY SAT.  DOWNSTREAM FROM THE
TROUGH...WEAK FLOW WILL PERSIST OVER TX...THE LWR MS VLY...AND THE
OH VLY...W OF SLOWLY PROGRESSIVE LOW ALONG THE CAROLINA CST. 

AT LWR LVLS...MDT LOW LVL SLY FLOW WILL PREVAIL OVER MUCH OF THE
PLNS E OF A NNE-SSW ORIENTED LEE TROUGH.  THE TROUGH WILL BE
OVERTAKEN FROM N TO S BY A REJUVENATED COLD FRONT...ASSOCIATED WITH
BC/AB UPR SYSTEM...THAT WILL MOVE E/SE ACROSS THE NRN HI PLNS/WRN
DAKOTAS LATER TODAY...AND ACROSS WRN PORTIONS OF THE CNTRL PLNS AND
THE ERN DAKOTAS TNGT/EARLY SAT.  THE LEE TROUGH AND COLD FRONT WILL
SERVE TO FOCUS TSTM DEVELOPMENT THIS AFTN AND EVE.  SOME OF THIS
ACTIVITY COULD BE STRONG TO SVR...ESPECIALLY OVER PARTS OF THE
DAKOTAS.  MODEST MOISTURE AVAILABILITY AND MODEST DEEP SHEAR
WILL...HOWEVER...LIKELY LIMIT THE INTENSITY...DURATION...AND
COVERAGE OF SVR WEATHER. 

...DAKOTAS INTO NRN MN THIS AFTN THROUGH TNGT...
CURRENT RAOBS...SFC OBS...AND BLENDED PW DATA SUGGEST THAT BOUNDARY
LAYER MOISTURE WILL REMAIN RELATIVELY LIMITED OVER THE NRN PLNS/UPR
MS VLY THIS PERIOD...WITH AVERAGE SFC DEWPOINTS THIS AFTN AND EVE
EXPECTED TO BE AOB THE MID 50S F IN WELL-MIXED AREAS AHEAD OF COLD
FRONT/LEE TROUGH.  POCKETS OF HIGHER DEW POINTS MAY EXIST ALONG WARM
FRONT IN NRN MN...BUT THESE LIKELY WILL BE ASSOCIATED WITH A LESS
DEEPLY MIXED BOUNDARY LAYER ENVIRONMENT.  

WHILE SPARSE MOISTURE WILL LIMIT BUOYANCY...COMBINATION OF SFC
HEATING...STEEP MID LVL LAPSE RATES...UPLIFT ALONG COLD FRONT/LEE
TROUGH...AND SLOWLY INCREASING LARGE SCALE FORCING FOR ASCENT  
SHOULD OVERCOME EML CAP AND SUPPORT A BAND OF AFTN/EVE STORMS FROM
WRN SD NNEWD INTO ERN ND.  AN ISOLD STORM OR TWO COULD FORM ALONG
LEE TROUGH SEGMENT IN CNTRL SD...AND A FEW STORMS ALSO COULD FORM
ALONG SHALLOW WARM FRONTAL ZONE NOW EVOLVING OVER FAR NRN MN. 

GIVEN STRENGTH OF CAP AND MOISTURE AVAILABILITY...THE MOST
CONCENTRATED ACTIVITY SHOULD EVOLVE INTO MULTICELL CLUSTERS ALONG
AND ATOP ACCELERATING COLD FRONT.  THESE COULD YIELD SVR HAIL AND
PERHAPS LOCALLY DMGG WIND INTO THIS EVE AS SBCAPE INCREASES TO AOA
1500 J/KG.  A SUPERCELL OR TWO ALSO MAY OCCUR...MOST LIKELY ALONG
LEE TROUGH IN CNTRL SD...AND/OR ALONG WARM FRONT IN NRN MN.  THESE
STORMS ALSO COULD PRODUCE SVR HAIL/WIND.  

...WY/CNTRL HI PLNS THIS AFTN/EVE...
INVERTED-VEE THERMODYNAMIC ENVIRONMENT WILL BE CONDUCIVE FOR SCTD
HIGH-BASED STORMS WITH A RISK FOR DRY MICROBURSTS FROM PARTS OF
WY/CO AND PERHAPS ERN UT NEWD INTO WRN NEB AS SFC HEATING FURTHER
DESTABILIZES REGION OF STRENGTHENING SWLY FLOW/ASCENT AHEAD OF COLD
FRONT.  SOME OF THESE STORMS COULD MERGE INTO SMALL CLUSTERS EARLY
TNGT.  

...FAR S FL THIS AFTN...
HIGH LVL WLY JET MAY YIELD AN ENHANCED THE RISK FOR A FEW PULSE
STORMS WITH STRONG WINDS OVER FAR S FL TODAY...WHERE PW WILL BE AOA
1.50 INCHES AND MID LVL TEMPS RELATIVELY COOL /AROUND MINUS 10C AT
500 MB/.

..CORFIDI/COHEN.. 05/18/2012

000
ACUS02 KWNS 180532
SWODY2
SPC AC 180531

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1231 AM CDT FRI MAY 18 2012

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL AND
SRN PLAINS...

...CENTRAL AND SRN PLAINS...

WEAK HEIGHT FALLS WILL OVERSPREAD THE CNTRL PLAINS DURING THE DAY2
PERIOD AS A SHORT-WAVE TROUGH EJECTS FROM CO/NM INTO NEB/KS/WRN OK
BY 20/00Z.  AS THIS FEATURE SHIFTS EAST SFC PRESSURE WILL RISE IN
THE LEE OF THE NRN/CNTRL ROCKIES FORCING A COLD FRONT TO A POSITION
FROM NRN MN...SWWD ACROSS SERN NEB INTO THE TX PANHANDLE BY PEAK
HEATING.  VERY WARM EML WILL BE IN PLACE ACROSS THE SLGT RISK REGION
EARLY SATURDAY WHICH WILL LIMIT PRE-FRONTAL CONVECTION WITHIN THE
ELONGATED WARM ADVECTION ZONE AHEAD OF THE COLD FRONT.  GIVEN THE
STRENGTH OF THE CAP IT APPEARS SFC TEMPERATURES WILL NEED TO WARM
SIGNIFICANTLY FOR CONVECTIVE DEVELOPMENT...ESPECIALLY SOUTH OF I-70.
EVEN SO...BOTH THE NAM AND GFS SUGGEST INTENSE BOUNDARY LAYER
HEATING WILL OCCUR AHEAD OF THE FRONT ACROSS KS/NWRN OK/TX
PANHANDLE.  THIS WILL WEAKEN THE CAP AND COMBINED WITH FRONTAL
CONVERGENCE SHOULD PROVE ADEQUATE FOR TSTMS TO DEVELOP ALONG/JUST
BEHIND THE ADVANCING WIND SHIFT TOWARD EARLY EVENING.  FORECAST
SOUNDINGS SUGGEST AMPLE DEEP LAYER SHEAR FOR ORGANIZED MULTI-CELL
UPDRAFTS AND PERHAPS EVEN A FEW SUPERCELLS.  LATEST DATA ALSO
SUGGESTS A CONCENTRATION OF POST-FRONTAL CONVECTION MAY BE NOTED DUE
TO THE AFOREMENTIONED STRONG WARM SECTOR CAP.  SOUNDINGS SUPPORT
CONVECTION IMMEDIATELY BEHIND THE FRONT EXTENDING TO THE CANADIAN
BORDER WHERE WEAKER INSTABILITY SHOULD LIMIT SEVERE THREAT SOMEWHAT.
GIVEN THE STEEPEST LAPSE RATES AND STRONGER INSTABILITY MAY BE
RESERVED TO THE CNTRL/SRN PLAINS IT APPEARS THE HIGHER PROBABILITIES
FOR SEVERE HAIL AND DAMAGING WINDS WILL BE NOTED ACROSS THESE AREAS.
WARM ADVECTION DURING THE OVERNIGHT HOURS SHOULD ENHANCE THE
LONGEVITY OF THIS CONVECTION AS IT SHIFTS SLOWLY EAST IN ASSOCIATION
WITH THE FRONTAL ZONE.

...ELSEWHERE...

SLOW-MOVING UPPER TROUGH/LOW WILL BE NOTED ALONG THE MIDDLE
ATLANTIC/SERN U.S. COAST.  WITH SFC RIDGING EXPECTED TO REMAIN
FIRMLY ENTRENCHED ALONG THE APPALACHIANS IT APPEARS THE GREATEST
CONCENTRATION OF CONVECTION WILL OCCUR NEAR THE NC COAST AND ACROSS
THE FL PENINSULA.  VERY ISOLATED TSTMS MAY ALSO DEVELOP DURING THE
HEAT OF THE DAY ACROSS PARTS OF THE TN VALLEY AND CNTRL GULF STATES
BUT WITH LIMITED FORCING AND THE LACK OF MEANINGFUL LOW LEVEL
CONVERGENCE THIS WILL PROVE QUITE SPARSE AND LIKELY WEAK.

..DARROW.. 05/18/2012

000
ACUS03 KWNS 180701
SWODY3
SPC AC 180700

DAY 3 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0200 AM CDT FRI MAY 18 2012

VALID 201200Z - 211200Z

...IL TO NWRN TX...

LATEST SHORT-RANGE MODEL GUIDANCE IS IN GENERAL AGREEMENT REGARDING
THE EVOLUTION OF EJECTING TROUGH DURING THE DAY2/3 TIME FRAME.  WITH
UPPER TROUGHING EXPECTED TO HOLD FIRM ACROSS THE SERN U.S...UPSTREAM
FEATURE SHOULD BEGIN TO TURN SEWD ACROSS THE MS VALLEY REGION LATE
WITH A BAND OF MODEST MID LEVEL FLOW EXPECTED TO TRANSLATE ACROSS
THE FRONTAL ZONE OVER THE SRN PLAINS.  THIS WILL BE COINCIDENT WITH
STEEPER LAPSE RATES AND SOMEWHAT STRONGER INSTABILITY FROM PORTIONS
OF NWRN TX INTO ERN OK.  OTHERWISE...A NARROW CORRIDOR OF HIGHER
MOISTURE WILL EXTEND THE LENGTH OF THE FRONTAL ZONE FROM NWRN TX
THROUGH THE MID MS VALLEY INTO THE UPPER GREAT LAKES.

MODELS AGREE THAT LOW LEVEL CONVERGENCE WILL PROVE GENERALLY WEAK
ALONG THE ADVANCING WIND SHIFT AND BOUNDARY LAYER HEATING SHOULD
PROVE INSTRUMENTAL IN CONVECTIVE DEVELOPMENT ALONG THE
FRONT...ESPECIALLY FROM IL SWWD INTO NWRN TX.  THIS PORTION OF THE
BOUNDARY SHOULD EXPERIENCE THE STEEPEST LAPSE RATES AND POTENTIALLY
PRODUCE THE STRONGER UPDRAFTS/DOWNDRAFTS.  FOR THIS REASON HAVE
OPTED TO ADD 5% SEVERE PROBS FOR TSTMS THAT DEVELOP ALONG/NEAR THE
COLD FRONT WHERE MARGINAL DEEP LAYER SHEAR WOULD SEEM SUPPORTIVE OF
MULTI-CELL UPDRAFTS AT BEST.  ISOLATED GUSTY WINDS AND HAIL WOULD BE
THE MORE SIGNIFICANT THREATS IF ROBUST CONVECTION CAN BECOME
ESTABLISHED DURING THE AFTERNOON/EVENING TIME FRAME.

..DARROW.. 05/18/2012

ACUS48 KWNS 180826
SWOD48
SPC AC 180826
DAY 4-8 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0326 AM CDT FRI MAY 18 2012
VALID 211200Z - 261200Z
...DISCUSSION...
LARGE SCALE FLOW REGIME WILL REMAIN DECIDEDLY HOSTILE FOR ORGANIZED
SEVERE THUNDERSTORMS ACROSS MUCH OF THE CONUS EARLY NEXT WEEK AS
LINGERING ERN U.S. TROUGH LIMITS MOISTURE/INSTABILITY FROM RETURNING
INLAND.  BY MID WEEK THE GFS IS MORE PROGRESSIVE WITH EJECTING SHORT
WAVES INTO THE PLAINS THAN THE ECMWF WHICH COULD OTHERWISE SUPPORT
SEVERE DEVELOPMENT.  HOWEVER...CONFIDENCE IS LOW REGARDING THE
EVOLVING PATTERN LATE IN THE PERIOD.
..DARROW.. 05/18/2012