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

000
ACUS01 KWNS 181629
SWODY1
SPC AC 181627

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1127 AM CDT FRI MAY 18 2012

VALID 181630Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN UT/SWRN WY INTO WRN
CO......

...ERN UT/SWRN WY INTO WRN CO...
WATER VAPOR IMAGERY SHOWS A STRONG UPPER TROUGH MOVING EWD ACROSS
THE GREAT BASIN THIS MORNING...ASSOCIATED WITH 70-100 M HEIGHT FALLS
AND -18C TEMPERATURE AT 500 MB.  DYNAMIC FORCING FOR LARGE SCALE
ASCENT AHEAD OF THE TROUGH COUPLED WITH FRONTAL LIFT ALONG AN
ADVANCING COLD FRONT HAS RESULTED IN A BAND OF TSTMS FROM THE SERN
ID/SWRN WY BORDER SSWWD INTO CENTRAL UT.  ENVIRONMENT DOWNSTREAM
FROM THE CONVECTIVE BAND IS CHARACTERIZED BY A DEEP SFC-BASED MIXED
LAYER AND AMPLE MID LEVEL MOISTURE.  VISIBLE IMAGERY SHOWS LIMITED
CLOUDS FROM PARTS OF ERN UT INTO SWRN WY...WITH CLOUDS EXPECTED TO
DIMINISH FROM THE WEST OVER WRN CO THIS AFTERNOON.  THIS WILL
PROMOTE STRONG DIABATIC HEATING THIS AFTERNOON AND EVENING...FURTHER
STEEPENING LAPSE RATES AND CONTRIBUTING TO DEVELOPMENT OF MUCAPE OF
500-1000 J/KG.  THE PRESENCE OF A DEEP MIXED LAYER WILL ALSO RESULT
IN LARGE VALUES OF DCAPE...INDICATING POTENTIAL FOR STRONG
DOWNDRAFTS ENHANCED BY EVAPORATIVE COOLING AND DRY ADIABATIC LAPSE
RATES.  THIS WILL RESULT IN A THREAT FOR STRONG/SEVERE WIND GUSTS AS
STORMS SPREAD/DEVELOP EWD THIS AFTERNOON AND EVENING.

...ERN WY INTO THE DAKOTAS...
A FRONTAL BOUNDARY WILL CONSOLIDATE FROM NERN ND SWWD INTO SERN WY
THIS AFTERNOON AS THE PRIMARY COLD FRONT MOVES EWD ACROSS ERN MT AND
NERN WY.  LOW LEVEL MOISTURE WILL CONTINUE TO BE A LIMITING FACTOR
WITH SURFACE DEW POINTS LIKELY REMAINING AOB 55F...BUT STEEP LAPSE
RATES WILL COMPENSATE TO SOME EXTENT ALLOWING MUCAPE TO REACH
1000-1500 J/KG.  LARGE SCALE FORCING FOR ASCENT ASSOCIATED WITH AN
UPSTREAM NRN TROUGH CURRENTLY OVER THE BC/ALTA REGION IS EXPECTED TO
LAG WELL WEST OF THE FRONTAL LOCATION...WITH MESOSCALE LIFT AND
SUBSEQUENT CONVECTIVE DEVELOPMENT MOST CONCENTRATED ALONG/WEST OF
THE SURFACE BOUNDARY.  THE STEEP LAPSE RATES AND LOW LEVEL MIXED
LAYER MAY SUPPORT HAIL AND A FEW STRONG WIND GUSTS WITH ISOLATED 
CONVECTIVE CELLS...BUT OVERALL SEVERE THREAT IS EXPECTED TO BE
LIMITED.  

...FAR S FL THIS AFTN...
HIGH LVL WLY JET MAY YIELD AN ENHANCED 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/.

..WEISS/GARNER.. 05/18/2012

000
ACUS02 KWNS 181728
SWODY2
SPC AC 181726

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT FRI MAY 18 2012

VALID 191200Z - 201200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM SERN NEB SSWWD INTO WRN OK
AND VICINITY...

...SYNOPSIS...
A WRN U.S. UPPER TROUGH IS FORECAST TO CONTINUE MOVING INTO THE
CENTRAL U.S. THIS PERIOD...WEAKENING WITH TIME AS ENCOUNTERS
LONGER-WAVELENGTH ERN U.S. RIDGING.  MEANWHILE WITHIN THE ERN U.S.
RIDGE...A WEAK UPPER LOW CENTERED INVOF THE COASTAL CAROLINAS IS
FORECAST TO LINGER THROUGH THE PERIOD.

AT THE SURFACE...A COLD FRONT IS FORECAST TO SHIFT ACROSS THE NRN
AND CENTRAL PLAINS...IN CONJUNCTION WITH THE PROGRESSING UPPER
TROUGH.  THIS FRONT WILL SERVE AS A FOCUS FOR THE MOST ACTIVE
CONVECTIVE THREAT THIS PERIOD.

...KS/OK AND VICINITY...
AS THE COLD FRONT CROSSES THE PLAINS THROUGH THE AFTERNOON...A
MODESTLY MOIST/HEATING BOUNDARY LAYER SHOULD RESULT IN WARM SECTOR
MIXED-LAYER CAPE RANGING FROM ROUGHLY 1000 TO 2000 J/KG.  THOUGH
CAPPING SHOULD HINDER DEVELOPMENT ACROSS THE SLIGHT RISK AREA
THROUGH EARLY TO MID AFTERNOON...LATER AFTERNOON DEVELOPMENT OF
ISOLATED TO SCATTERED STORMS IS EXPECTED -- INITIALLY FARTHER NORTH
ACROSS THE LOWER PROBABILITY RISK AREA OF MN/ERN SD AND THEN SWD
WITH TIME ACROSS ERN NEB/CENTRAL KS/WRN OK.  WITH 40-PLUS KT
MID-LEVEL SWLYS SPREADING ACROSS THE SERN NEB/KS/OK WARM SECTOR IN
CONJUNCTION WITH THE EJECTING SHORT-WAVE TROUGH ASSUMING AN
INCREASINGLY NEGATIVE TILT...SHEAR PROFILES WILL BE FAVORABLE FOR
ROTATING UPDRAFTS.  THUS...A FEW SUPERCELLS CAPABLE OF PRODUCING
LARGE HAIL AND DAMAGING WINDS ARE EXPECTED.  A TORNADO OR TWO WILL
ALSO BE POSSIBLE...THOUGH THIS THREAT SHOULD BE SOMEWHAT MITIGATED
BY THE RELATIVELY DRY/WELL-MIXED BOUNDARY LAYER EXPECTED TO EXIST.

THOUGH A FAIRLY STRONG LOW-LEVEL JET MAY ALLOW STORMS TO CONTINUE
OVERNIGHT ACROSS PARTS OF THE PLAINS REGION...SEVERE THREAT SHOULD
DIMINISH AFTER DARK AS THE BOUNDARY LAYER COOLS AND STORMS BECOME
MORE ELEVATED WITH TIME.

..GOSS.. 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