Public Weather Alerts for Canada,,,,,,,,,,https://weather.gc.ca/warnings/index_e.html

SPC Jun 28, 2014 1630Z Thunderstorm Outlook

Jun 28, 2014 1630 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK
   1130 AM CDT SAT JUN 28 2014

   VALID 281630Z - 291200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS ACROSS THE
   MIDDLE MO AND UPPER MS VALLEYS...

   ...SUMMARY...
   CONSIDERABLE THUNDERSTORM ACTIVITY APPEARS LIKELY THIS AFTERNOON AND
   EVENING FROM PARTS OF THE SOUTHERN PLAINS AND LOWER TO MID MISSOURI
   VALLEY NORTHWARD INTO THE UPPER MISSISSIPPI VALLEY. SOME OF THESE
   STORMS MAY BE ACCOMPANIED WITH DAMAGING WIND GUSTS AND HAIL.

   ...SRN PLAINS INTO LOWER MO VALLEY...
   CONVECTIVE COMPLEX OVER NRN OK IS PROGRESSING EWD/SEWD AND HAS
   MAINTAINED AN ISOLATED SEVERE RISK DURING THE MORNING.  THE MCS IS
   LOCATED ALONG THE SRN PART OF THE NEGATIVELY TILTED UPPER TROUGH
   EXTENDING FROM WRN SD INTO FAR WRN OK...AND AS THIS SYSTEM BEGINS TO
   LIFT NEWD TOWARD THE LOWER MO VALLEY...INCREASING LARGE SCALE ASCENT
   WILL OVERSPREAD THE LOW LEVEL MOISTURE/INSTABILITY AXIS FROM CENTRAL
   OK INTO CENTRAL MO.  EXTENSIVE CLOUD COVER REMAINS OVER THIS REGION
   WHICH WILL LIMIT THE INTENSITY OF DIABATIC HEATING ACROSS THE
   BROADER REGION...BUT BREAKS IN CLOUD COVER MAY PERMIT LOCALIZED
   POCKETS OF STRONGER INSTABILITY TO DEVELOP.  

   VISIBLE IMAGERY/RADAR SHOW STORMS DEVELOPING ALONG THE LEADING EDGE
   OF THE NRN OK MCS AND EXTENDING NEWD ALONG A PRE-FRONTAL BOUNDARY
   FROM SERN KS INTO WEST CENTRAL MO WHERE OBJECTIVE MESOANALYSIS
   FIELDS INDICATE CIN IS DIMINISHING.  WINDS ALOFT BACK IN THE
   MID-LEVELS TO A MORE SOUTHERLY COMPONENT WITH LARGELY UNIDIRECTIONAL
   SHEAR SUGGESTING POTENTIAL FOR SHORT LINEAR CONVECTIVE SEGMENTS TO
   DEVELOP.  VERTICAL SHEAR OF 30-35 KT IN THE LOWEST 6 KM AND MODERATE
   INSTABILITY WITH MLCAPE OF 1500-2000 J/KG WILL PROMOTE STRONG/SEVERE
   STORMS WITH LARGE HAIL AND DAMAGING WIND GUSTS THE PRIMARY THREAT
   DURING THE AFTERNOON AND EVENING.

   OTHER MORE ISOLATED STORMS MAY DEVELOP ALONG/AHEAD OF THE NRN OK MCS
   AS THE OUTFLOW MOVES SEWD/SWD OVER WRN/CENTRAL OK AND THE ERN TX
   PANHANDLE WHERE STEEP LAPSE RATES ARE CONTRIBUTING TO AN
   INCREASINGLY UNSTABLE AIR MASS...WITH MLCAPE REACHING 2000-2500 J/KG
   THIS AFTERNOON.  DYNAMIC FORCING FOR ASCENT WILL BE DIMINISHING AS
   THE UPPER TROUGH BEGINS TO LIFT NE OF THE AREA THIS AFTERNOON AND
   HEIGHTS RISE...HOWEVER CONVERGENCE ALONG THE OUTFLOW AND ZONES OF
   ENHANCED HEATING MAY BE SUFFICIENT FOR CURRENT STORMS TO INTENSIFY
   ALONG THE LEADING EDGE OF THE SYSTEM.  LARGE HAIL AND DAMAGING WIND
   GUSTS WILL BE POSSIBLE INTO THE EVENING HOURS.

   ...MIDDLE MO VALLEY INTO THE UPPER MS VALLEY...
   A PRE-FRONTAL CONVERGENCE BOUNDARY IS EVIDENT IN VISIBLE SATELLITE
   IMAGERY ARCING FROM LOW OVER CENTRAL ND ACROSS ARCING SERN ND INTO
   SWRN MN AND WRN IA.  THIS MAY PROVIDE A FOCUS FOR NEW THUNDERSTORM
   DEVELOPMENT THIS AFTERNOON AS HIGHER SURFACE DEW POINTS AROUND 70
   ARE LOCATED ALONG/AHEAD OF THE BOUNDARY.  CLOUDS AHEAD OF THE
   BOUNDARY WILL LIKELY INHIBIT TO SOME EXTENT THE MAGNITUDE OF
   DIABATIC HEATING AND DESTABILIZATION...HOWEVER...INCREASING LARGE
   SCALE ASCENT AHEAD OF THE APPROACHING UPPER TROUGH WILL ENHANCE
   CONVECTIVE POTENTIAL DURING THE AFTERNOON.  A FEW STRONG/SEVERE
   STORMS ARE EXPECTED IN ASSOCIATION WITH SEVERAL LINEAR SEGMENTS AS
   THEY PROGRESS EWD/NEWD ACROSS THE REGION.  ADDITIONAL STORMS ARE
   ALSO EXPECTED TO DEVELOP ALONG/AHEAD OF THE SURFACE FRONT AS IT MOVE
   EWD/NEWD ACROSS THE AREA WITH MODEL GUIDANCE INDICATING NEW STORMS
   FORMING OVER ERN PARTS OF SD AND NEB LATER THIS AFTERNOON.  STRONGER
   CELLS WILL BE CAPABLE OF LARGE HAIL AND DAMAGING WIND GUSTS.

   ...WRN KS/SRN NEB LATE TONIGHT...
   A STRONG LOW LEVEL JET IS FORECAST TO DEVELOP OVER THE SRN HIGH
   PLAINS LATER TONIGHT WHICH WILL TRANSPORT LOW LEVEL MOISTURE NWD
   INTO WRN KS AND POSSIBLY SRN NEB.  WARM ADVECTION AND CONVERGENCE AT
   THE NOSE OF THE LLJ MAY PROMOTE DEVELOPMENT OF PRIMARILY ELEVATED
   STORMS LATE IN THE PERIOD.  MODEL GUIDANCE IS NOT CONSISTENT IN THE
   PREDICTION OF STRONG STORMS WITH THE OPERATIONAL AND PARALLEL NAM
   PARENT RUNS SHOWING A STRONGER INSTABILITY AND PRECIPITATION SIGNAL.
   THE 5 PER CENT HAIL AREA HAS BEEN TRENDED WWD INTO WRN KS AND SRN
   NEB FOR THIS LATE PERIOD POSSIBILITY AND WILL AWAIT LATER
   OBSERVATIONAL AND MODEL GUIDANCE TO FURTHER ASSESS THE THREAT.

http://www.lightningmaps.org/realtime?lang=en

Prévision nationale des risques orageux,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,http://www.keraunos.org/previsions/prevision-orage-tornade-france-convective-outlook.html

VALIDITE : SAM 28 JUIN 2014 06Z -> DIM 29 JUIN 2014 06Z
EMIS LE : 28/06/2014 A 08H LOC

 

 

PREVISION GLOBALE TOUS RISQUES CONVECTIFS	PROBABILITE DE TORNADE
	PROBABILITE DE GRÊLE > 2 cm

 

QUALIFICATION GENERALE DU RISQUE CONVECTIF...
Risque de forts orages venteux, grêligènes et très pluvieux entre les Pyrénées, le Massif-Central, le Jura et les Vosges. La probabilité d'orages violents (rafales > 120 km/h ou grêle > 5 cm) est faible, la probabilité d'orages forts (rafales de 90 à 120 km/h, grêle > 2 cm) est par contre bien plus élevée.

 

 

ANALYSE SYNOPTIQUE ET DE MESO-ECHELLE...

Un thalweg d'altitude très dynamique abordera la Bretagne en milieu de nuit prochaine. A l'avant, le flux de SO drainera une masse d'air chaude et fortement instable entre le sud-ouest le nord-est du pays. Un premier forçage d'altitude se présentera sur le centre-est en cours d'après-midi à l'avant du forçage principal qui balaiera l'ensemble de l'axe SO/NE entre la soirée et la fin de nuit prochaine.

Continental Europe animation

European Storm Forecast Experiment

Mesoscale Discussion

Mesoscale Discussion
Valid: Sat 28 Jun 2014 14:00 to Sat 28 Jun 2014 21:00 UTC
Issued: Sat 28 Jun 2014 14:39
Forecaster: VAN DER VELDE

...France to southwestern Germany...

A surface low pressure center lies currently (14Z) at the west coast of France (Bordeaux). A large Atlantic upper trough moves into the region and will provide destabilization of the mid and upper levels, which is needed as 12Z soundings still show inversions at 900 and 450 hPa. A stationary frontal zone is well-defined by thermal gradients and a sharp wind shift (NE/S) running from some 100km north of Bordeaux to Stuttgart approximately.

Observed surface mixing ratios in France vary at 13Z between 10.5 and 13 g/kg with potential temperatures ranging between 26 and 32°C, the higher values over the Massif Central.
Inserting these values into Bordeaux and Nimes 12Z soundings, the cap can be bypassed in some locations and some 1000 J/kg SBCAPE could be obtained, but MLCAPE will be lower and mixed parcels may have some trouble with the cap.

In fact, satellite shows initiation over northern Massif Central oriented SW-NE and along the front in the west (WSW-ENE). The storms will grow in a strong kinematic environment with large but relatively straight hodographs. Observed Bordeaux 600 hPa wind is 60 kts with 40 kts at 900 hPa. This directly translates into a primary threat of severe convective wind gusts, especially as cold pools join into an MCS. Deep layer shear values of 15-20 m/s and SREH of 150 m²/s² initially and over 250 m²/s² predicted by GFS at 18Z (SW France) support supercells. 0-1 km shear ranges from 10 m/s in the afternoon to over 15 m/s during the evening (GFS). Together with relatively low LCL (descending to <1000 m in the evening) this underlines potential for tornadoes, and supports bow echoes. Large hail will be possible as well, but the upper level inversion represents a mixed phase region without much buoyancy which could be a limiting factor.

After 18Z the mid level cold front comes in from the west and will likely trigger storms in SW France moving upscale to a somewhat parallel-stratiform MCS over the southeastern quarter of France (this will happen beyond the validity time of this MD).