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July 21-22 Severe Threat


snowlover2

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SPC just issued a moderate risk for most of the southern half of MN and into western WI for tomorrow.

 

 

 

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1230 PM CDT SUN JUL 20 2014  
 
VALID 211200Z - 221200Z  

   
..THERE IS A MDT RISK OF SVR TSTMS FOR FAR SERN ND...NERN SD
 
MUCH  
OF CENTRAL AND SRN MN...AND PART OF WEST CENTRAL/NWRN WI...  
 
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM  
THE DAKOTAS EWD THROUGH THE UPPER MIDWEST...  
   
..SUMMARY
 
 
SEVERE STORMS APPEAR INCREASINGLY LIKELY ACROSS PARTS OF THE UPPER  
MIDWEST FROM MONDAY LATE AFTERNOON INTO TUESDAY MORNING. DAMAGING  
WINDS...SOME WITH SPEEDS TO HURRICANE-FORCE...SHOULD BE THE PRIMARY  
HAZARD. HOWEVER...A TORNADO THREAT AND LARGE HAIL CANNOT BE RULED  
OUT.  
   
..SYNOPSIS
 
 
A STRONG MID-UPPER LEVEL ANTICYCLONE WILL REMAIN ANCHORED OVER NM  
THROUGH DAY 2...WITH SOME HEIGHT RISES EXPECTED MONDAY MORNING  
ACROSS CENTRAL MN AND NRN WI AS THE NERN EXTENT OF THE RIDGE BUILDS  
EWD INTO THE GREAT LAKES. MEANWHILE...OF GREATER SIGNIFICANCE TO  
THE SEVERE WEATHER THREAT FROM MONDAY AFTERNOON TO TUESDAY MORNING  
IS MODELS AGREEING WITH THE TIMING OF A WELL-DEFINED SHORTWAVE  
TROUGH EXPECTED TO MOVE INTO THE CENTRAL DAKOTAS MONDAY AFTERNOON.  
THIS FEATURE IS CURRENTLY MOVING NWD THROUGH THE GREAT BASIN AND IS  
FORECAST TO ACCELERATE EWD WITHIN THE SRN EXTENT OF THE WLYS FROM  
THE NRN PLAINS TO THE UPPER GREAT LAKES REGION BY 12Z TUESDAY. AT  
THE SURFACE...A CYCLONE SHOULD BECOME CENTERED OVER CNTRL SD MONDAY  
AFTERNOON WITH A QUASI-STATIONARY FRONT NEAR THE ND/SD BORDER INTO  
NRN MN. A WIND SHIFT WILL TRAIL WWD FROM THE SURFACE LOW TO INVOF  
THE MT/WY BORDER...WHERE A LOWER SEVERE PROBABILITY IS EXPECTED. A  
40-45 KT SWLY LLJ IS EXPECTED TO EXTEND INTO NRN IA/SRN MN MONDAY  
NIGHT TO EARLY TUESDAY MORNING.  
   
..UPPER MIDWEST
 
 
GIVEN THE DEGREE OF INSTABILITY EXPECTED ACROSS PARTS OF THE ERN  
DAKOTAS EWD TO WRN WI MONDAY AFTERNOON/EVENING /MLCAPE EXCEEDING  
4000 J PER KG/ AND THE MODEL AGREEMENT IN TIMING OF THE GREAT BASIN  
SHORTWAVE TROUGH...CONFIDENCE CONTINUES TO INCREASE FOR THE  
POTENTIAL OF A FORWARD-PROPAGATING MCS FROM MONDAY EVENING TO EARLY  
TUESDAY MORNING. SEVERE WIND GUSTS...SOME AT HURRICANE-FORCE...WILL  
BE POSSIBLE ACROSS NERN SD...SERN ND...MUCH OF CENTRAL AND SRN MN  
INTO WRN WI RESULTING IN AN UPGRADE TO A MODERATE RISK FOR THIS  
REGION.  
 
THE THERMODYNAMIC SETUP REMAINS SIMILAR TO THE INITIAL DAY 2  
ISSUANCE...WITH CONTINUED EVAPOTRANSPIRATION AND POLEWARD MOISTURE  
TRANSPORT YIELDING INCREASINGLY RICH BOUNDARY LAYER MOISTURE BENEATH  
AN EML CAPPING INVERSION ACROSS ERN SD INTO CNTRL/SRN MN. SURFACE  
DEW POINTS WILL REACH INTO THE 70S AS MEAN MIXING RATIOS APPROACH  
18-20 G/KG. WITH VERY STEEP MID-LEVEL LAPSE RATES AROUND 7.5-9.0 DEG  
C/KM IN THE 700-500 MB LAYER...AN EXTREMELY UNSTABLE AIR MASS SHOULD  
DEVELOP.  
 
LARGE-SCALE ASCENT ATTENDANT TO THE PROGRESSIVE SHORTWAVE TROUGH  
WILL MOVE INTO ND/NRN SD MONDAY AFTERNOON. THIS ASCENT COMBINED  
WITH ISENTROPIC LIFT SHOULD RESULT IN A MIX OF SCATTERED ELEVATED  
AND SURFACE-BASED STORMS BY MID-LATE AFTERNOON. ALTHOUGH STRONGER  
MID-LEVEL WLYS WILL BE CONFINED TO THE CANADIAN PRAIRIES...  
SUFFICIENT DEEP-LAYER SHEAR WILL EXIST FOR MULTICELLS/TRANSIENT  
SUPERCELLS SUPPORTING ALL SEVERE HAZARDS WITH THE INITIAL STORMS. A  
CONTINUED LIKELIHOOD EXISTS FOR MLCIN BEING MINIMIZED NEAR THE  
SURFACE CYCLONE AND ADJACENT WARM SECTOR WHERE SURFACE TEMPERATURES  
SHOULD REACH AT LEAST THE UPPER 90S. THUS...AN AMALGAMATION OF  
UPDRAFTS SHOULD YIELD A DEEPENING COLD POOL...WITH AN UPSCALE GROWTH  
INTO AN MCS --- PRODUCING SVR WIND GUSTS --- APPEARING TO BE MORE  
LIKELY THE ERN DAKOTAS INTO MN AND WRN WI THROUGH MONDAY NIGHT/EARLY  
TUESDAY MORNING.  
 
..PETERS.. 07/20/2014  

 

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Moderate risk area pulled pretty far to the NW and decreased in size. MSP now just in the slight risk.

I dig the tiny Milwaukee/Chicago slight risk area D2.

 

Yeah, that's one of the smaller Day 2 risks I remember seeing issued, although it does cover a large population center.

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0z 4km NAM breaks out discrete convection across nrn IL/SE WI between 0-3z as does the op NAM but looks more widespread. Will be interesting to watch if we do get CI and how long it holds off. With extreme instability/moisture and maybe 35kts of shear. Who knows

 

Yeah I'm hoping I can get out and shoot some lightning tomorrow night, but not sure if we'll see convection unzip this far southwest along the CF.

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Clear skies, and bright sunshine.  Currently 84 here with a Dew Point of 69. Wind is SSW @ 8 with gusts to about 20 right now.  Feels muggy out there, only saving grace is the breeze.  Getting new windows put in today (nice landlord have I ) so, the AC is off until they finish, which should be in about an hour or so. 

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New outlook sounds a bit pessimistic

 

 


DAY 1 CONVECTIVE OUTLOOK    NWS STORM PREDICTION CENTER NORMAN OK  0255 PM CDT TUE JUL 22 2014    VALID 222000Z - 231200Z    ...THERE IS A SLGT RISK OF SVR TSTMS FROM KS/MO INTO SOUTHWEST LOWER  MI...    ...THERE IS A SLGT RISK OF SVR TSTMS OVER THE BLACK HILLS AND  ADJACENT REGIONS...     ..THERE IS A SLGT RISK OF SVR TSTMS OVER CNTRL OREGON       ..SUMMARY    SCATTERED SEVERE STORMS WITH WIND AND HAIL WILL OCCUR LATER TODAY  AND TONIGHT FROM THE CENTRAL PLAINS EAST-NORTHEAST TO SOUTHERN LAKE  MICHIGAN. A CLUSTER OF SEVERE STORMS IS POSSIBLE OVER THE BLACK  HILLS REGION...AND MORE ISOLATED WIND AND HAIL STORMS MAY OCCUR OVER  INTERIOR PORTIONS OF THE PACIFIC NORTHWEST.     ..KS/MO INTO SOUTHERN LAKE MI REGION    LATEST HI-RES MODEL GUIDANCE FROM THE HRRR SUGGESTS CONVECTIVE  COVERAGE THROUGH EVENING IS EXPECTED TO REMAIN SPARSE AT BEST. WHILE  SOME SHOWERS AND STORMS HAVE BEEN ONGOING ACROSS EASTERN IA...THEY  HAVE STRUGGLED TO INTENSIFY/ORGANIZE AS A STRONG CAP REMAINS OVER  THE REGION...DUE IN PART TO EARLIER CONVECTION/CLOUD COVER ACROSS  THE IA/MO/IL TRI-STATE AREA. A FEW STRONG TO SEVERE STORMS WILL  REMAIN POSSIBLE FROM SE WI INTO KS AHEAD OF THE COLD FRONT IF THEY  CAN BREACH THE CAP. BUT THE GREATER THREAT MAY DEVELOP OVERNIGHT  ACROSS PARTS OF KS/MO/IL...AS SUGGESTED BY THE 12Z NSSL-WRF. ANY  CONVECTION DEVELOPING OVERNIGHT WOULD LIKELY BE ELEVATED AND POSE  MAINLY A HAIL THREAT. GIVEN CURRENT TRENDS...THE SLIGHT RISK HAS  BEEN TRIMMED ON THE NORTH AND WESTERN EDGES AS WELL AS ACROSS PARTS  OF SRN IL INTO IND.  
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   MESOSCALE DISCUSSION 1433

   NWS STORM PREDICTION CENTER NORMAN OK

   0554 PM CDT TUE JUL 22 2014

   AREAS AFFECTED...NRN IL...SERN WI THROUGH WRN LOWER MI

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

   VALID 222254Z - 230100Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...STORMS MIGHT BECOME CAPABLE OF PRODUCING ISOLATED LARGE

   HAIL AND STRONG WIND GUSTS FROM SERN WI THROUGH WRN LOWER MI THIS

   EVENING. CONFIDENCE IN A MORE ROBUST SEVERE EVENT IS NOT

   PARTICULARLY HIGH...BUT TRENDS ARE BEING MONITORED.

   DISCUSSION...EARLY THIS EVENING A FEW STORMS HAVE DEVELOPED ALONG A

   SEWD MOVING COLD FRONT FROM NCNTRL LAKE MI SWWD INTO SERN WI. LATEST

   OBJECTIVE ANALYSIS AND FORECAST SOUNDING DATA SHOW THE ATMOSPHERE TO

   BE VERY UNSTABLE IN THE PRE-FRONTAL WARM SECTOR WITH 3000-3500 J/KG

   MLCAPE. HOWEVER...WARM TEMPERATURES AT BASE OF AN EML HAVE ADVECTED

   THROUGH MUCH OF WARM SECTOR WHICH...IN ADDITION TO APPARENT MODEST

   FRONTAL CONVERGENCE...SUGGESTS STORMS MIGHT STRUGGLE AS THEY TRY TO

   DEVELOP SEWD...ESPECIALLY WITH ONSET OF NOCTURNAL COOLING.

   NEVERTHELESS...A CONDITIONAL THREAT FOR LARGE HAIL AND DAMAGING WIND

   GUSTS EXISTS GIVEN THE DEGREE OF INSTABILITY AND MODERATE

   UNIDIRECTIONAL DEEP-LAYER WINDS.

 

 

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Had a light rain shower from a decaying high-based storm a bit ago, but that atomic cap has prevented just about all convection. Some of these mesoscale model members have a ridiculous tendency to forecast copious convection when capping is present. 14C at 700mb is about as strong as it gets.

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