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April Pattern Discussion


jaxjagman

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Euro 12z sped up the system on todays run towards the end of the work week.It's showing some cape of 1.5k+ in the western Valley,showalter -4 Thursday.Some wet bulbs of 10-11k ft,still looks capped.Lots of energy floating around south of the valley looking at the 500 mb.It still has potential.

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DAY 4-8 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0357 AM CDT SUN MAR 30 2014

   VALID 021200Z - 071200Z

   ...DISCUSSION...
   DAY 4-5/

   MODELS APPEAR TO BE CONVERGING TOWARD A SLOWER...MORE AMPLIFIED
   SOLUTION REGARDING THE UPPER TROUGH FORECAST TO MOVE THROUGH THE
   CNTRL AND SRN PLAINS AND MID MS VALLEY AREA BY THURSDAY /DAY 5/ WITH
   ECMWF ALSO TRENDING SLOWER...BUT STILL REMAINS THE FASTER MODEL.
   PRECEDING THIS FEATURE...RICHER GULF MOISTURE /LOW-MID 60S
   DEWPOINTS/ WILL ADVECT THROUGH THE WARM SECTOR UNDERNEATH STEEP
   MID-LEVEL LAPSE RATES RESULTING IN MODERATE-STRONG INSTABILITY OVER
   THE SRN PLAINS AND A PORTION OF THE LOWER MS VALLEY BY WEDNESDAY
   /DAY 4/. IT STILL APPEARS A FEW SEVERE STORMS COULD DEVELOP ALONG
   THE DRYLINE DAY 4 OVER THE SRN PLAINS AND NEAR THE DRYLINE/FRONT
   INTERSECTION OVER NWRN OK/SWRN KS. HOWEVER...CAPPING WILL BE A
   CONCERN FOR SEVERE STORM COVERAGE ALONG THE DRYLINE AS WELL AS
   FARTHER EAST IN WARM SECTOR. CONFIDENCE IN WHERE TO PLACE A 30% OR
   GREATER SEVERE AREA REMAINS LOW FOR DAY 4...BUT A CATEGORICAL RISK
   AREA WILL PROBABLY BE NEEDED FOR THE NEXT DAY 3 UPDATE.

   GIVEN MODEL TRENDS...IT NOW APPEARS A MORE SUBSTANTIAL SEVERE THREAT
   MIGHT DEVELOP FROM THE SRN PLAINS INTO THE LOWER-MID MS VALLEY
   REGION THURSDAY /DAY 5/ AS THE SHORTWAVE TROUGH EJECTS ENEWD
   RESULTING IN HEIGHT FALLS ACROSS THE WARM SECTOR AND A STRENGTHENING
   LLJ. STORMS MAY DEVELOP ALONG THE DRYLINE AND DRYLINE/PACIFIC FRONT
   MERGER OVER THE SRN PLAINS AS WELL AS FARTHER EAST IN THE WARM
   SECTOR. SEVERE THREAT WILL LIKELY SPREAD EWD INTO THE LOWER MS
   VALLEY AREA BY LATER THURSDAY AFTERNOON AND EVENING.

   DAY 6/

   SEVERE THREAT WILL PROBABLY DEVELOP FARTHER EAST INTO THE OH AND TN
   VALLEYS AS WELL AS A PORTION OF THE SERN STATES BY FRIDAY /DAY 6/.
   IF CURRENT TRENDS PERSIST...A PORTION OF THIS REGION MAY BE INCLUDED
   IN A CATEGORICAL RISK IN THE NEXT UPDATE.

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Euro weeklies Thursday evening hinted at an active final third of April. I was encouraged for a couple days. Unfortunately weekend ensemble runs revert back to the ridge west trough east train wreck. Best we could do is more Gulf Coastal front junk. Tough to get action up into the Mid South and the Plains can just about forget it. Hope the weekend NWP is wrong. MJO confusion seems to be driving model forecasts.

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Monteagle might end as snow per correlation coefficient CC on dual pole radar. Chatty will probably stay too warm. Shocking right? Meanwhile northeast Tenn (TRI) stands a good chance of ending as snow. Per CC the back end of that precip crossing the Upper Plateau is consistently staying snow. This should be it. 6-15 day pattern shows no strong cold fronts.

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Have had big, sloppy wet flakes here in Morristown for about the last hour now. Right now it's just about 100% snow actually and it's really been coming down hard!! It's very strange with the trees blooming an the green grass. It's pretty but it looks like things are not happy

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Instability parameters aren't the only ones involved in a severe setup, with the 00z Euro solution, there is a lot more making that a potent solution than just instability. For example, the trough has a broad base allowing forcing to overspread the warm sector well ahead of any boundary and allowing discrete convection to develop. In addition, the position of the surface low would be pretty favorable for a severe event in Dixie Alley and there are strong wind fields present through the column. Obviously it's a ways out and things will change, but this is a period to watch.

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12Z Euro echos/strengthens the forecast above. Iff it is a perfect prog Monday will feature a Mid South Mauler severe wx set-up. Long way out and lots can go wrong, but confidence is good deep moisture will be in place. We have no just-in-time Plains moisture issue over in the South - it'll be juicy. Euro runs hint at new jet stream energy pushing out of TX/OK after the weekend Plains system ejects into the Upper Midwest. New surface low is shown developing in the Middle Mississippi Valley. If all the above comes together the Mid South faces all severe weather threats on Monday. It is Day 7 and it is just a forecast, but certainly interesting to discuss.

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DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0351 AM CDT WED APR 23 2014

VALID 261200Z - 011200Z

...DISCUSSION...
..SIGNIFICANT MULTI-DAY SEVERE EVENT EXPECTED ACROSS PORTIONS OF THE
CENTRAL AND SOUTHERN PLAINS SATURDAY AND SUNDAY AND ACROSS THE MS
VALLEY AND MID SOUTH ON MONDAY...STRONG TORNADOES ARE POSSIBLE...

MEDIUM RANGE FORECAST CONTINUES TO BE HEAVILY WEIGHTED TOWARD THE
ECMWF DUE TO RUN-TO-RUN CONSISTENCY REGARDING THE 500MB EVOLUTION OF
WRN U.S. TROUGH. CONCERNS REGARDING POLAR FRONT UNDERCUTTING STRONG
SWLY FLOW ALOFT HAVE ABATED THIS MORNING. LATEST GUIDANCE DEEPENS
LEE CYCLONE OVER SERN CO SATURDAY AFTERNOON WITH SUBSEQUENT MOVEMENT
INTO WRN KS ON SUNDAY. INTENSE 500MB SPEED MAX APPROACHING 90KT
SHOULD ROUND THE BASE OF THE TROUGH ALONG THE AZ/MEXICAN BORDER THEN
EJECT INTO SWRN KS EARLY SUNDAY. AS A RESULT SFC LOW IS NOT
EXPECTED TO ADVANCE APPRECIABLY EWD UNTIL LATER MONDAY AS SECONDARY
MID-LEVEL SPEED MAX DEVELOPS FROM NORTH TX INTO THE LOWER OH RIVER
VALLEY.

MODERATE TO EXTREME INSTABILITY SHOULD DEVELOP EAST OF THE DRYLINE
SATURDAY AFTERNOON ALONG ERN PLUME OF STEEP LAPSE RATES. STRONGLY
DIFLUENT FLOW ALOFT SHOULD ENCOURAGE VIGOROUS SUPERCELL DEVELOPMENT
FROM PORTIONS OF WCNTRL TX...NWD INTO KS. VERY LARGE HAIL AND
TORNADOES CAN BE EXPECTED WITH THIS ACTIVITY.

IT/S NOT ENTIRELY CLEAR HOW FAR EAST THE DRYLINE WILL MIX SUNDAY AS
LOWEST PRESSURES WILL REMAIN FOCUSED ACROSS THE HIGH PLAINS OF WRN
KS. MODELS MIX DRYLINE EAST OF I-35 CORRIDOR ACROSS OK BY 18Z
SUNDAY BUT THE DAY5 FORECAST WILL ACCOUNT FOR DRYLINE NOT MIXING
ACROSS THE PLAINS AS FAST AS MODELS CURRENTLY DEPICT. AS A
RESULT...SUBSTANTIAL MID-LEVEL FLOW SHOULD OVERSPREAD THE
MOIST/BUOYANT WARM SECTOR AND ANOTHER DIURNALLY-INITIATED ROUND OF
POTENTIALLY TORNADIC SUPERCELLS COULD EVOLVE.

LATER MONDAY IT APPEARS THE SFC FRONT/DRYLINE SHOULD ADVANCE INTO
THE MS VALLEY. SCATTERED-NUMEROUS SUPERCELLS SHOULD EVOLVE AHEAD OF
THE FRONT FROM LA...NWD INTO MO AND POSSIBLY AS FAR EAST AS MIDDLE
TN. TORNADOES AND LARGE HAIL REMAIN POSSIBLE WITH WARM-SECTOR
CONVECTION.

..DARROW.. 04/23/2014

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