69 replies to this topic

[MnWeatherman]

All models now showing a strong shortwave to impact North Dakota, South Dakota and Minnesota on Friday. Could possibly have a large severe weather event unfold if runs persist. GFS is back on board...

[Buckeye05]

Multi-day event it looks like. The 4th and the 5th look the most interesting to me.

[andyhb]

I'd like to see a better LL wind response to be more confident in this, although obviously it's a bit early to get into finer details. It's nice to finally see the Pac jet begin to gain some steam again as we move into the latter part of Summer.

Still, the persistence of this feature within the models warrants attention and should be watched closely as we approach the weekend. FWIW, the GFS brings another upper trough across the northern States right after the initial shortwave.

[StormDude81]

Upper Plains on Friday, and Great Lakes and Ohio Valley on Saturday, shows a threat for a two day significant severe weather outbreak

[andyhb]

Upper Plains on Friday, and Great Lakes and Ohio Valley on Saturday, shows a threat for a two day significant severe weather outbreak

Yeah, let's not be throwing around language like this until we are closer in time period.

I don't agree with this statement either, btw.

[StormDude81]

Yeah, let's not be throwing around language like this until we are closer in time period.

I don't agree with this statement either, btw.

I know, but it has some potential, at the least we will see some severe storms during this period

[Buckeye05]

I know, but it has some potential, at the least we will see some severe storms during this period

I know it's been a while, but try not to use the words "significant" and "outbreak", unless you have reason to . This system has high hype potential, and looks rather "meh" per the last GFS in my opinion, for the Dakotas at least.

[StormDude81]

I know it's been a while, but try not to use the words "significant" and "outbreak", unless you have reason to . This system has high hype potential, and looks rather "meh" per the last GFS in my opinion, for the Dakotas at least.

Yep, We just have to wait and see what the models show in the upcoming days, and also last thursday during the Moderate Risk in the east, i ended having two rounds of decent severe weather

[MnWeatherman]

00Z GFS looks healthy for Friday, perhaps the best run thus far.

[andyhb]

00Z GFS looks healthy for Friday, perhaps the best run thus far.

Meh. LL wind fields are still looking crappy except for areas across southeastern SD, which will likely have EML problems indicated by the warm H7 temps. Not exactly enthused at this point, although as I mentioned, it's nice to finally see some decent mid level flow somewhere in the CONUS besides east of the GL.

[MnWeatherman]

Yeah, would definitely agree the LL wind fields are pretty crappy, if your referencing to the supercell/tornado potential, but severe weather in general appears pretty likely.

[Minnesota Meso]

Directional wind fields in the lower levels look good, but increasing speed through H85 looks poor, we really don't get much speed shear until H7 through H5, but this may be splitting hairs at this point in time, it's a long ways off and I agree it will be interesting to watch for MN on Friday. What I find more interesting though is how the through once it passes through MN develops a bit of a negative tilt as moves through WI on Saturday, we will have to see what transpires at the lower levels to see how this all play out.

[Buckeye05]

Liking the looks of Minnesota and Wisconsin. Also check out this day 4-8.


MEDIUM RANGE GUIDANCE INDICATES THAT A STRONG SHORT WAVE IMPULSE
WILL DIG SOUTHEAST OF THE CANADIAN ROCKIES BY THE BEGINNING OF THE
FORECAST PERIOD...BEFORE ACCELERATING THROUGH THE STRONGER
WESTERLIES NEAR THE CANADIAN/U.S. BORDER LATE THIS WEEK THROUGH NEXT
WEEKEND. SPREAD AMONG THE MODEL DATA BEGINS TO INCREASE RAPIDLY BY
FRIDAY/SATURDAY AS THE IMPULSE APPROACHES WHAT COULD STILL BE A
STRONGLY CONFLUENT REGIME BETWEEN THE SOUTH CENTRAL U.S. SUBTROPICAL
RIDGE...AND THE NORTHEASTERN CANADIAN POLAR VORTEX...WHICH MAY BE IN
THE PROCESS OF REDEVELOPING EASTWARD. THIS ALSO GENERALLY COINCIDES
WITH MODEL TIMING OF STRONGER SURFACE CYCLOGENESIS...WHICH COULD BE
ACCOMPANIED BY AN ORGANIZED SEVERE WEATHER THREAT...POSSIBLY
INCLUDING THE RISK FOR TORNADOES...ACROSS PARTS OF THE GREAT LAKES
REGION. AT THE PRESENT TIME...THIS POTENTIAL APPEARS HIGHEST ACROSS
PARTS OF WISCONSIN AND MICHIGAN NEXT SATURDAY /AUGUST 4/...BUT
UNCERTAINTIES ARE STILL TOO LARGE TO CONFIDENTLY DELINEATE A
REGIONAL SEVERE THREAT AREA.

[andyhb]

Yeah, if anything, Aug 4th looks potentially to be the best out of this time period, strongly worded Day 4-8 confirms that...although the 12z GFS doesn't look quite as favourable across this area.

[andyhb]

12z GFS is now becoming quite interesting across the Northern Plains on Friday, with the associated vort max to the shortwave becoming negatively tilted, spreading a 40-60 kt H5 jet streak across and inducing a rather strong low level wind response within a strongly unstable warm sector that likely would be favourable for potential tornadic development. H7 temps are still a concern though.

[MnWeatherman]

Haven't seen numbers this high in quite awhile! Waiting for the 18Z GFS to see if there's any consistency to this...

[andyhb]

18z is weaker with the LL response, thus the numbers will probably be lower.

[MnWeatherman]

18z is weaker with the LL response, thus the numbers will probably be lower.

18z was a let down...

[andyhb]

Yeah, southwestern MN was just primed in that 12z run, outside of potential EML issues, the raw parameters were nasty...

3500+ J/kg of ML and SBCAPE, LCL heights under 800 m, effective SRH of 350+ m2/s2, effective shear of 50+ kts...

[MnWeatherman]

Well, at least it's evident that it doesn't take much of a LL wind field to skyrocket the tornado likelihood. I still wouldn't rule out the tornado potential, unless Thursday's runs are similar to this garbage.

[Buckeye05]

Sounds Marginal...

"NORTHERN AND CENTRAL PLAINS...
DOWNSTREAM OF THE SHORT WAVE TROUGH DIGGING ACROSS THE WESTERN
INTERNATIONAL BORDER/NORTHERN U.S. ROCKIES REGION...CLUSTERS OF
STORMS APPEAR POSSIBLE THURSDAY AND THURSDAY NIGHT. ACTIVITY LIKELY
WILL BE SUPPORTED BY DEVELOPING ZONES OF STRONGER LOWER/MID
TROPOSPHERIC WARM ADVECTION ON THE EASTERN EDGE OF WARMER AND MORE
STRONGLY CAPPING ELEVATED MIXED LAYER AIR ADVECTING EAST OF THE
ROCKIES. SUFFICIENT LOW-LEVEL MOISTURE IS EXPECTED TO EXIST ACROSS
THE REGION TO CONTRIBUTE TO MODERATELY LARGE CAPE WITH STRONG
BOUNDARY LAYER HEATING BENEATH STEEP MID-LEVEL LAPSE RATES. THIS
ENVIRONMENT PROBABLY WILL PROVE CONDUCIVE TO THE PRODUCTION OF LARGE
HAIL AND DAMAGING WIND GUSTS IN STRONGER CONVECTION. THIS MAY
BECOME ENHANCED BY INCREASING DEEP LAYER SHEAR...PARTICULARLY ACROSS
SOUTH DAKOTA DURING THE LATE AFTERNOON AND EVENING...WHERE/WHEN
PRIMARY STRENGTHENING OF MID/UPPER FORCING FOR UPWARD VERTICAL
MOTION ACROSS THE NORTHERN PLAINS IS ANTICIPATED."

[Minnesota_storms]

This looks very interesting to me.

Yeah, southwestern MN was just primed in that 12z run

here
We could use the rain. all of us. Hoping this brings a lot.

[andyhb]

This looks very interesting to me.


here
We could use the rain. all of us. Hoping this brings a lot.

That was the 12z run yesterday, fyi.

[Minnesota Meso]

MPX is cranking up their wording in the Afternoon AFD, but they put out the caveat of timing. To me, as of now It looks more like overnight Friday which should limit it some what, but I still have concerns for WI on Saturday. And I know that statement covers two different threads so I apologize in advance.

OVER THE PAST FEW DAYS...MODELS HAVE BEEN TRENDING TOWARD A
PERSISTENT...STRONG DIFLUENT FLOW /SOUTHERN-NORTHERN JET
INTERACTION/ ACROSS THE NORTHERN PLAINS FRIDAY. THESE TWO JETS
WILL COMBINE TO CREATE A POWERFUL JET OF 100-110 KT JET ACROSS MN
SATURDAY. BASED ON THE LATEST SFC AND UPPER UPPER PARAMETERS OF
THE GFS/EC...THIS SYSTEM HAS THE POTENTIAL OF A SIGNIFICANT SEVERE
WX OUTBREAK. ALTHOUGH THE SFC FRONT IS FORECAST TO BE EAST OF OUR
FA SATURDAY AFTN...IF THIS FRONT SLOWS A BIT...SVR WX COULD
DEVELOP ACROSS THE EASTERN FA SATURDAY AFTN. IN ADDITION TO THE
SVR WX POSSIBILITIES...STRONG UPPER DIFLUENT SHOULD CREATE THE
ENVIRONMENT OF A LINE OR NUMEROUS SHRA/TSRA LATE FRIDAY
NIGHT...INTO SATURDAY MORNING. THERE STILL REMAINS SOME
UNCERTAINTIES IN TERMS OF THE ORIENTATION OF THE LLJ AND SFC LOW
ALONG THE CANADIAN BORDER. BEST FORCING/MOISTURE REMAINS JUST
NORTH OF OUR FA...BUT DUE TO STRENGTH ALONE OF THIS
SYSTEM...SHRA/TSRA SHOULD DEVELOP.

[andyhb]

00z GFS/NAM definitely paint Minnesota as a potential hot spot Friday afternoon/evening, with access to a backed low level wind field across most of the state, with locally stronger LL shear closer to the sfc low and warm front, and the mid level jet nosing into the state from the west, shear/forcing should be adequate, add that in with expected August moisture/instability fields and apparent manageable LCL heights and EML temps, could be an active day across the state, as the latest AFD suggests...

Still a tad early IMO to be really interested, but it is getting there, to an extent. Stronger LL flow would certainly make this more potentially volatile.

[MnWeatherman]

Still not seeing much of a real tornado threat for Friday. If 850mb southerly winds are able to ramp up to 35kt+, then I,ll get excited.

[andyhb]

Still not seeing much of a real tornado threat for Friday. If 850mb southerly winds are able to ramp up to 35kt+, then I,ll get excited.

You probably will only need around 25-30 kts, remember this is August and we have plenty of instability to partially offset lower shear, that said, I would like to see some ramping up also, and there are other factors that could screw up this as well, as with any severe setup.

D3 mentioning possible discrete supercells ahead of the front, although keeping the wording modest for now, which I agree with.

...NRN PLAINS INTO UPR MS VLY/UPR GREAT LAKES REGION... DESPITE THE AFOREMENTIONED UNCERTAINTIES...IT SEEMS MORE PROBABLE THAN NOT THAT SUFFICIENT DESTABILIZATION AND STRENGTHENING OF SHEAR WILL TAKE PLACE...IN THE PRESENCE OF INCREASING LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION...TO SUPPORT SLIGHT RISK PROBABILITIES ACROSS THE EASTERN DAKOTAS THROUGH MUCH OF MINNESOTA FRIDAY/FRIDAY NIGHT. DISCRETE SUPERCELLS MAY NOT BE OUT OF THE QUESTION ALONG AND AHEAD OF A SOUTHEASTWARD ADVANCING COLD FRONT...HOWEVER IT SEEMS CONVECTION IS MORE LIKELY TO TAKE THE FORM OF ONE OR TWO EVOLVING STORMS CLUSTERS...OR A BROKEN SQUALL LINE...BY FRIDAY EVENING...WITH DAMAGING WIND GUSTS AND HAIL THE MORE PROMINENT SEVERE THREATS.

[MnWeatherman]

LL wind fields look good on the 12z NAM and GFS

[andyhb]

Yes...yes they do.

SYSTEM ON FRIDAY HAS THE POTENTIAL FOR WIDESPREAD THUNDERSTORMS AND WHAT LOOKS LIKE THE BEST SEVERE THREAT WE HAVE HAD IN A WHILE. FAVORABLE UPPER FLOW PATTERN WITH THE SUBTROPICAL AND POLAR JETS COMING TOGETHER AND GOOD THICKNESS DIFFLUENCE OUT AHEAD OF THE UPPER LOW AND COOLING HEIGHTS SUGGEST LIKELY POPS. THERE WILL ALSO BE NICE OVERLAP OF SHEAR AND INSTABILITY. GFS HAS 40-55KTS AT 500MB BY 06Z SATURDAY TO GO ALONG WITH 2000-2500 J/KG OF MUCAPE. THE UPPER LOW LOOKS MORE LIKE SOMETHING TYPICALLY OBSERVED IN SEPT/OCT...BUT WITH AUGUST WARMTH. A LITTLE WARM AT 850-700MB...BUT 9-11C AT 700MB IS NOT A SHOW STOPPER BY ANY MEANS. PRIMARY AREA OF FOCUS IS IN CENTRAL MN AND NORTHWEST WI.

[andyhb]

CIPS Warm Season for the 12z NAM at 60 hrs is popping 6/17/10 as an analog...

[Buckeye05]

CIPS Warm Season for the 12z NAM at 60 hrs is popping 6/17/10 as an analog...

Geez. Skeptical of anything that prolific but still...

[andyhb]

NAM also has most of Minnesota capped on Friday, so I'm still rather cautious to approach this, although MPX's wording certainly raised an eyebrow.

[Buckeye05]

700mb rule does not apply in the Northern Plains due to higher ground elevation according to John Daviess. I'm not really sure how to judge capping in that case.

[andyhb]

700mb rule does not apply in the Northern Plains due to higher ground elevation according to John Daviess. I'm not really sure how to judge capping in that case.

That's a good point, forgot about that. The H7 temps aren't overly inhibiting in this case anyway, FGF's CWA looks good per the 00z NAM.

[nwburbschaser]

Do you see much of a tornado threat Andy?