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July 10-18 Severe Possibilities


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WRFs want to develop a line in W IA and dive it SSE and miss most of E. IA/N IL. Then you have the NAM that progresses much faster and has the line well into central IL by 00z. Then there's the GFS, with similar cold front position as previous runs but instability is displaced east. tstms might have developed and used the CAPE farther west though. (Dew point looks a bit odd on that sounding, if that means anything.)gfs_2016071212_036_42.0--91.5.png

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MESOSCALE DISCUSSION 1257

NWS STORM PREDICTION CENTER NORMAN OK

0320 PM CDT TUE JUL 12 2016

AREAS AFFECTED...PORTIONS OF MICHIGAN...NORTHERN INDIANA...AND FAR

EASTERN ILLINOIS

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 122020Z - 122145Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...CLUSTERS/LINES OF THUNDERSTORMS WILL CONTINUE TO DEVELOP

AND ADVANCE EAST THIS AFTERNOON...FAVORING OCCASIONAL

STRONG/MARGINALLY SEVERE WIND GUSTS. HOWEVER...THE SEVERE THREAT

SHOULD REMAIN ISOLATED ENOUGH TO PRECLUDE WATCH ISSUANCE.

DISCUSSION...AIDED BY A SHORTWAVE TROUGH LIFTING NORTHEAST ACROSS

THE UPPER GREAT LAKES...A SMALL LINE OF CONVECTION HAS ORGANIZED

ACROSS WESTERN PORTIONS OF LOWER MICHIGAN THIS AFTERNOON. LOW-LEVEL

CONVERGENCE ALONG A SFC TROUGH AND A CORRIDOR OF HIGHER THETA-E

ALONG/AHEAD OF THIS LINE SHOULD ENSURE THAT STORMS PERSIST FOR THE

NEXT SEVERAL HOURS AS THEY MOVE EASTWARD. ADDITIONALLY...FURTHER

DEVELOPMENT SHOULD OCCUR FARTHER SOUTH ALONG THE TROUGH...TOWARDS

NORTHERN INDIANA.

REGIONAL VWP DATA EXHIBIT AROUND 30-40 KTS OF SOUTHWESTERLY FLOW IN

THE 2-5 KM LAYER...AND DOWNWARD TRANSFER OF THIS MOMENTUM THROUGH A

WELL-MIXED BOUNDARY LAYER SHOULD ENCOURAGE AT LEAST A FEW STRONG

WIND GUSTS. ADDITIONALLY...A FAIRLY UNIDIRECTIONAL WIND PROFILE

SHOULD MAINTAIN GENERALLY LINEAR/CLUSTER STORM MODES...ALSO FAVORING

PRIMARILY A WIND THREAT. NONETHELESS...A LACK OF STEEPER MID-LEVEL

LAPSE RATES AND STRONGER DEEP SHEAR SHOULD KEEP THE OVERALL THREAT

RELATIVELY LOW. AS SUCH...WATCH ISSUANCE IS NOT ANTICIPATED.

..PICCA/THOMPSON.. 07/12/2016

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Maybe a chance for severe weather in IN/MI/OH tomorrow. CAPE may be above 3000 J/kg early in the day. A small shortwave in the 500mb flow should kick off some storms, with 0-6km shear possibly 30kts.

Agreed, I'm cautiously optimistic for tomorrow seeing as there's no real convection behind the line right moving through now. 

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Agreed, I'm cautiously optimistic for tomorrow seeing as there's no real convection behind the line right moving through now. 

There should be some convection that forms near the Missouri/Iowa border later tonight that will move ENE.  How that evolves will definitely have an impact on tomorrow

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Agreed, I'm cautiously optimistic for tomorrow seeing as there's no real convection behind the line right moving through now. 

The 18z 4km NAM and 12z WRF-ARW both look downright nasty near Hillsdale.  Still though, the shear values should be 30 knots-ish so it would be pretty unlikely to get highly organized supercells.

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New day 1

 

 

 DAY 1 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   1154 PM CDT TUE JUL 12 2016

   VALID 131200Z - 141200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE AREA FROM THE
   CNTRL PLAINS INTO THE UPPER GREAT LAKES...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE SRN HIGH PLAINS ACROSS
   THE CNTRL PLAINS AND INTO THE OH VALLEY AND GREAT LAKES...

   ...SUMMARY...
   SCATTERED SEVERE THUNDERSTORMS WILL BE POSSIBLE WEDNESDAY FROM THE
   CENTRAL PLAINS NORTHEASTWARD ACROSS THE GREAT LAKES WITH WIND THE
   MAIN THREAT.

   ...SYNOPSIS...
   THE MAIN UPPER TROUGH WILL EXTEND FROM ONTARIO SWWD ACROSS THE NRN
   PLAINS DURING THE DAY...AND WILL TAKE ON MORE OF A POSITIVE TILT
   OVERNIGHT AS IT SHIFTS INTO THE GREAT LAKES. A BELT OF RELATIVELY
   STRONG MID TO HIGH-LEVEL FLOW WILL SPREAD EWD ACROSS MUCH OF THE
   REGION WITH MAIN JET CORE FROM THE MID MO VALLEY NEWD ACROSS THE
   GREAT LAKES. AT THE SURFACE...LOW PRESSURE WILL SHIFT NEWD ACROSS
   ONTARIO WITH A WEAKER SECONDARY LOW OVER THE SRN PLAINS. IN BETWEEN
   THE TWO LOWS WILL BE A RATHER WEAK SFC PATTERN WITH A WEAK BOUNDARY
   FROM CNTRL KS INTO ERN NEB/IA BY LATE AFTERNOON. S OF THIS
   BOUNDARY...AMPLE MOISTURE AND INSTABILITY WILL EXIST WITH UPPER 60S
   TO LOWER 70S F DEWPOINTS BENEATH COOL MIDLEVEL TEMPERATURES.

   ...CNTRL PLAINS INTO THE GREAT LAKES AND OH VALLEY...
   INITIALLY...THE LOW-LEVEL JET WILL BE SWLY/VEERED WITH WARM
   ADVECTION FOCUSED ACROSS IL WHERE SOME EARLY AND WEAK THUNDERSTORM
   ACTIVITY IS EXPECTED. SPORADIC SEVERE IS POSSIBLE AS THIS EARLY
   ACTIVITY CONTINUES EWD ACROSS MO/IL/IND/LOWER MI AND OH DURING THE
   AFTERNOON WITH ISOLATED DAMAGING WIND POSSIBLE. TO THE W...STRONG
   HEATING WILL OCCUR NEAR THE SFC TROUGH ACROSS THE CNTRL HIGH PLAINS
   WITH A COOLER BUT MORE MOIST AIR MASS OVER ERN NEB AND KS NEWD
   TOWARD LAKE MICHIGAN. STRONG INSTABILITY WILL ALREADY BE IN PLACE
   EARLY IN THE DAY OVER THE CNTRL PLAINS WITH EARLY INITIATION
   DEPICTED BY SEVERAL MODELS OVER ERN KS/NEB INTO IA. STEEP LAPSE
   RATES ALOFT AND LONG HODOGRAPHS SUGGEST SOME HAIL THREAT WITH THESE
   STORMS.  BY AFTERNOON...INDICATIONS ARE THAT AN MCS MAY FORM IN
   CLOSER PROXIMITY TO THE WARMER AIR MASS ALONG THE I-70 CORRIDOR ON
   THE NOSE OF THE LOW-LEVEL JET. DAMAGING WINDS AND HAIL WOULD BE THE
   MAIN THREATS INTO THE EVENING WITH THE GREATEST RISK ACROSS ERN
   KS...SERN NEB...MO...SRN IA AND WRN IL. WHILE A CORRIDOR OF GREATER
   SEVERE WIND RISK MAY EXIST WITHIN THE OVERALL
   SLIGHT...PREDICTABILITY ISSUES GIVEN SUBTLE SFC PATTERN AND EFFECTS
   OF EARLY ACTIVITY CURRENTLY PRECLUDE AN UPGRADE TO ENHANCED RISK.


   ELSEWHERE...VERY STRONG HEATING WILL LIKELY LEAD TO ISOLATED STORMS
   OVER THE SRN HIGH PLAINS WITH A THREAT OF HAIL FOR A FEW HOURS.
   LAPSE RATES WILL BE STEEP SFC AND ALOFT...WITH WEAK BUT VEERING
   WINDS WITH HEIGHT SUPPORTING A FEW SLOW-MOVING CORES.

   ..JEWELL/ROGERS.. 07/13/2016

 

post-4544-0-88075900-1468387663_thumb.gi

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The NAM / 4km NAM really has a good environment for severe weather in northern Missouri and eastern Iowa tomorrow. 3400-5000 J/kg of CAPE and 50kt of effective shear. Low 0-3km SRH values would make for a lower chance of low-level mesocyclones and tornadoes, but medium 0-3km SRH values could develop later in the day in Missouri.

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