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June 1st - 12th Severe Weather Thread


andyhb

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Interesting looking threat tomorrow as well for areas closer to my backyard...

...CNTRL AND WRN MT...NRN ID...ERN WA...

STRONG HEATING WILL CONTRIBUTE TO MODERATE INSTABILITY...AND

SCATTERED STORMS ARE LIKELY BY AFTERNOON...FORMING ON THE HIGHER

TERRAIN INCLUDING THE ID/WRN MT BORDER FROM SMN TO GTF...AS WELL AS

ACROSS S CNTRL MT NEAR BILLINGS. LARGE HAIL AND DAMAGING WINDS WILL

BE POSSIBLE IN BOTH AREAS...BUT WRN MT/NRN ID AND ERN WA WILL HAVE

THE MOST FAVORABLE SHEAR PROFILES FOR SUPERCELLS WHICH COULD ALLOW

FOR A FEW HAILSTONES TO APPROACH 1.75 - 2.00 INCHES. ISOLATED

TORNADOES WILL BE POSSIBLE...ESPECIALLY IF LCL HEIGHTS END UP BEING

AT LEAST MARGINALLY LOW. THE STRONG FLOW AND STEEP LAPSE RATES ALSO

SUGGEST A FEW STORMS MAY BOW WITH AN ENHANCED WIND THREAT.

THE SEVERE THREAT WILL EXTEND FARTHER W ACROSS NRN ID AND ERN

WA...AND PERHAPS FAR NERN ORE...AND...THE THREAT MAY PERSIST WELL

INTO THE EVENING AS THE BULK OF THE UPPER HEIGHT FALLS AND COLD

FRONT EMERGE. THE ZONE IMMEDIATELY ALONG AND E OF THE COLD FRONT

WILL HAVE THE MOST FAVORABLE SHEAR PROFILES FOR TORNADOES...WITH AT

LEAST MARGINAL INSTABILITY REMAINING LATE.

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Day 6 and 7 highlighted on the new Day 4-8...second time this year that a D7 has been outlooked...

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0357 AM CDT MON JUN 04 2012

VALID 071200Z - 121200Z

..DISCUSSION

MEDIUM-RANGE MODELS IN FAIRLY GOOD AGREEMENT THROUGH THE

MEDIUM-RANGE PERIOD THIS RUN...WITH BOTH DEPICTING A SLOW EJECTION

OF THE WRN U.S. TROUGH/LOW EWD ACROSS THE INTERMOUNTAIN REGION DAYS

4-5 /THU. AND FRI. JUNE 7-8/ AND INTO/ACROSS THE PLAINS THROUGH THE

REMAINDER OF THE PERIOD.

SOME SEVERE POTENTIAL CAN BE EXPECTED DAY 4 ACROSS THE NRN PLAINS AS

A WEAK SHORT-WAVE FEATURE MOVES THROUGH THE MEAN RIDGE...AND THEN

DAY 5 OVER THE NRN INTERMOUNTAIN REGION AS THE MAIN TROUGH BEGINS

PROGRESSING ACROSS THE NWRN CONUS.

HOWEVER...A MORE WIDESPREAD THREAT SHOULD EVOLVE BEGINNING DAY 6

/SAT. JUNE 9/...AS CONTINUED EWD PROGRESS OF THE UPPER TROUGH/LOW

ACROSS THE INTERMOUNTAIN REGION DRIVES A STRONG COLD FRONT INTO THE

NRN PLAINS REGION. IT APPEARS ATTM THAT THIS THREAT SHOULD CONTINUE

DAY 7 /SUN. JUNE 10/ -- OVER THE NRN PLAINS/UPPER MS VALLEY...WITH

SOME THREAT POSSIBLY EXTENDING SWWD ACROSS THE CENTRAL PLAINS WHERE

MODELS HINT AT SECONDARY LOW DEVELOPMENT ALONG THE TRAILING PORTION

OF THE FRONT.

LATE IN THE PERIOD...THE GFS BECOMES A BIT FASTER WITH THE EWD

MOVEMENT OF THE SYSTEM...AND THUS CONFIDENCE IS LIMITED DAY

8...PRECLUDING INTRODUCTION OF ANY THREAT AREA. HOWEVER...WILL

INTRODUCE DAY 6 AND DAY 7 RISK AREAS -- FOCUSED OVER THE NRN PLAINS

REGION DAY 6 AND EXTENDING EWD TOWARD THE UPPER MS VALLEY DAY 7.

WITH A VERY UNSTABLE AIRMASS LIKELY TO BE IN PLACE AHEAD OF THE

FRONT AND AMPLE SHEAR EXPECTED...FAIRLY WIDESPREAD POTENTIAL FOR

LARGE HAIL AND DAMAGING WINDS -- AND POSSIBLY A COUPLE OF TORNADOES

-- WARRANTS INTRODUCTION OF THE THREAT AREAS THIS FORECAST.

..GOSS.. 06/04/2012

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Will end this thread on the 10th now that we have a possible synoptically evident event on the horizon this weekend.

Derek should take interest into this as well, I will also inform my relatives in Manitoba to watch the weather closely.

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Will end this thread on the 10th now that we have a possible synoptically evident event on the horizon this weekend.

Derek should take interest into this as well, I will also inform my relatives in Manitoba to watch the weather closely.

I am definitely interested. Both the GFS and Euro are showing good potential. Looks like a good MCS threat for southern MB Saturday night with a surface based threat on Sunday afternoon/early evening.

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Parts of MT about to be upgraded to a tornado watch...

MESOSCALE DISCUSSION 1059

NWS STORM PREDICTION CENTER NORMAN OK

0628 PM CDT MON JUN 04 2012

AREAS AFFECTED...W/N-CNTRL MT

CONCERNING...SEVERE THUNDERSTORM WATCH 354...

VALID 042328Z - 050030Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 354

CONTINUES.

SUMMARY...PORTIONS OF WW 354 IN W/N-CNTRL MT WILL BE UPGRADED TO A

TORNADO WATCH BY 00Z.

DISCUSSION...A COUPLE OF SUPERCELLS CROSSING THE CONTINENTAL DIVIDE

SHOULD PROGRESS INTO AN INCREASINGLY FAVORABLE AIR MASS FOR

POTENTIAL TORNADIC DEVELOPMENT BY EARLY EVENING. ALTHOUGH SURFACE

DEW POINT DEPRESSIONS AROUND 25 TO 35 DEG F AT GTF/HLN ARE CURRENTLY

A MITIGATING FACTOR TO TORNADIC POTENTIAL...SURFACE DEW POINTS HAVE

INCREASED INTO THE MIDDLE TO UPPER 50S AT HVR TO LWT. WITH LOW-LEVEL

ELYS EXPECTED TO STRENGTHEN WITH APPROACH OF SHORT WAVE TROUGH OVER

NRN CA...ADVECTION OF RICHER LOW-LEVEL MOISTURE COMBINED WITH

INCREASING LOW-LEVEL SHEAR WILL INCREASE THE TORNADIC RISK THIS

EVENING.

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Impressive wording on the tornado watch for MT, 50/50 tor probs...

DISCUSSION...SUPERCELLS MENTIONED IN SVR WW 354 ARE EXPECTED TO

STRENGTHEN AND DEVELOP LWR BASES AS THEY ENCOUNTER INCREASINGLY

MOIST LOW LVL ESELY FLOW ACROSS N CNTRL MT. GREAT FALLS MT VWP

SAMPLES THE 25 KT ELY CURRENT VERY WELL. WITH THE LOW LVL ELY FLOW

LIKELY TO STRENGTHEN AS THE CA/ORE UPR TROUGH ASSUMES MORE OF A

NEGATIVE TILT/ACCELERATES NNEWD...AND AS TEMP-DEW POINT SPREADS

DECREASE LATER THIS EVE...ENVIRONMENT WILL BECOME MORE FAVORABLE FOR

LOW LVL MESOCYCLONES/POSSIBLE TORNADOES. A CONDITIONAL RISK WILL

EXIST FOR ONE OR TWO STRONG TORNADOES.

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...A TORNADO WARNING REMAINS IN EFFECT UNTIL 845 PM MDT FOR NORTH

CENTRAL CHOUTEAU COUNTY...

AT 819 PM MDT...TRAINED WEATHER SPOTTERS REPORTED A FUNNEL CLOUD

NEAR HIGHWAY 87 NORTH OF LOMA. THIS DANGEROUS STORM IS LOCATED 12

MILES NORTH OF LOMA...OR 20 MILES WEST OF BIG SANDY...MOVING NORTH

AT 40 MPH.

THE TORNADO WILL OTHERWISE REMAIN OVER MAINLY RURAL AREAS OF

CHOUTEAU COUNTY.

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Still learning the model thing here but I noticed that the best wind/shear parameters don't overlay the best CAPE/Instability. They look to be separated by the front. This might lead to a lack of upper level support I would assume? Just thinking this could be a caveat, but correct me if i'm wrong.

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Still learning the model thing here but I noticed that the best wind/shear parameters don't overlay the best CAPE/Instability. They look to be separated by the front. This might lead to a lack of upper level support I would assume? Just thinking this could be a caveat, but correct me if i'm wrong.

This has been a recurring theme of 2012. You'll look at the H5 forecast for a particular medium-range setup and get excited, only to later realize the front is 300 miles southeast of the best dynamics. This is being discussed over at Stormtrack, as well. A couple people have mentioned this tends to be the result of troughs becoming positive-tilt during ejection into the Plains, of which we've had no shortage whatsoever lately.

Actually, though, the 12z GFS looks more optimistic than last night's. Solid 40-50 kt. midlevel flow overspreads the dryline in central ND on Saturday afternoon. I still don't like the lack of strong, backed low-level flow, though; a slightly more progressive solution likely would help here. As of now I don't see myself making the 15-hour haul for this setup, but if later solutions trend toward a 30+ kt. LLJ and more low-level hodograph curvature, that could change. Not having a passport, I'd also need a near-guarantee that the setup won't shift north at the last minute (as N Plains events so often do), since that would put it into MB. :lol:

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Gotta say, with some of these verbatims (particularly the GFS), Saturday is one of the more impressive synpotic setups I've seen for Southern Manitoba in some time, could be right in Derek's wheelhouse. I'd consider taking a trip out there to visit relatives and chase if I wasn't so busy this upcoming week and a half.

This will likely highly depend on the placement of the warm front though.

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