March 26th-28th Severe Thread

[andyhb]

Based on evidence from the models, it appears a strong short wave will eject eastward from the Rockies early next week. Timing is still a bit up in the air (Euro is a bit slower than the GFS), but it appears some severe threat should exist on Tuesday and perhaps Wednesday as the fast moving feature increases upper level support, initiates strong surface cyclogenesis and a strong LLJ out of the SSW/SW develops on its east side. Instability looks plentiful, especially considering the GFS is notorious for underestimating such values this far out. There are 60s dews into Northern Minnesota and Wisconsin and the SPC mentions it in their latest Day 4-8 outlook. There are a few things that I would like to see stronger (0-6 km shear would be one of them, but vectors out of the WSW and due westerly in places should ensure they are rather perpendicular to the incoming boundary). A fast moving system like this will likely not have the problems associated with a lack of forcing out ahead of the boundary (and in turn, breaking the cap). Details on possible kinematics are bit sketchy, but a shortwave like this in thermodynamics like the following has often lead to trouble...

H5 at 150 hrs on the 12z GFS:

CAPE at 153 hrs:

Dewpoints at 156:

Snippet from Day 4-8:

WITH THIS SYSTEM DEPARTING BY DAY 5...FOCUS FOR CONVECTIVE WEATHER

SHIFTS WWD INTO THE PLAINS STARTING DAY 6 /MON 3-26/. WHILE

LARGE-SCALE RIDGING WILL LIKELY REMAIN STRONG ENOUGH OVER THE

CENTRAL THIRD OF THE CONUS TO LIMIT POTENTIAL DAY 6...A BIT GREATER

SEVERE THREAT APPEARS EVIDENT ATTM FOR DAY 7 /TUE 3-27/...AS THE GFS

AND ECMWF SHOW A BREAKDOWN OF THE RIDGE AS AN UPPER TROUGH EJECTS

NEWD ACROSS THE INTERMOUNTAIN WEST TOWARD THE PLAINS. BY THIS TIME

HOWEVER...THE MODEL DIFFERENCES ON THE SMALL SCALE AFFECT CONFIDENCE

REGARDING LOCATION AND TIMING OF SURFACE FEATURES...TO THE DEGREE

THAT GREATER CORRIDORS OF CONVECTIVE POTENTIAL ARE DIFFICULT TO

DETERMINE AT THIS TIME. FURTHER...WITH PRIOR SURFACE RIDGING ACROSS

THE GULF WHICH SHOULD LIMIT QUALITY AND SPEED OF NWD RETURN OF

LOW-LEVEL MOISTURE INTO THE PLAINS -- AND THUS WOULD MODULATE THE

OVERALL DEGREE OF THREAT...THESE FACTORS PRECLUDE AREAL OUTLINE

ATTM.

CONVECTIVE THREAT WOULD APPEAR LIKELY TO CONTINUE INTO DAY 8 /WED

3-28/...THOUGH SHIFTED EWD INTO THE MIDWEST AND POSSIBLY SWD INTO

THE SRN PLAINS. AGAIN THOUGH...UNCERTAINTY REGARDING LOCATION AND

DEGREE OF THREAT PRECLUDES ISSUANCE OF AN OUTLOOK AREA ATTM.

Snippet from Gil Sebenste's outlook on his blog:

Next week...another cold front coming through on Tuesday could give us thunderstorms

then...and the latest GFS model even shows a chance of storms on Monday

on a warm front. Uncertainty is high with the latter, so I am keeping Monday dry for

the moment. But Tuesday or early Wednesday, we could see some thunderstorms that

might be worth writing home about if we get enough heating and moisture out

ahead of it. Highs on Sunday should be in the 60s, and then, as southerly

winds return, we go back into the 70s perhaps on Monday and likely on Tuesday

before the colder air comes in.

Snippet from MPX's AFD:

THE LATEST MEDIUM AND LONG RANGE MODELS CONTINUE TO DEPICT A

SHORTWAVE TROUGH FORECAST TO STRENGTHEN OVER THE NORTHERN PLAINS

EARLY NEXT WEEK. MUCH OF THE DYNAMICS AND FORCING DEVELOPS OVER THE

NORTHERN HALF OF OUR FORECAST AREA. STRONG CONVECTION COULD DEVELOP

OVER WEST CENTRAL MN AHEAD OF THE THICKNESS RIDGE TUESDAY

AFTERNOON/EVENING. MODEL INDICATING SOME COOLER AIR SPILLING INTO

CENTRAL MN TUESDAY NIGHT AND WEDNESDAY.

[Hoosier]

Something to watch over the coming days. Regardless of the magnitude of the severe threat, yet another abnormally far north threat for this time of year.

[andyhb]

Also of note, several of the GFS ensemble members are significantly stronger with the trough and associated height falls than the OP...

[andyhb]

Discussion from FGF, note the highlighted part:

.LONG TERM (SAT NIGHT THROUGH WED)...

A POTENTIALLY ACTIVE PERIOD MAY DEVELOP BY EARLY NEXT WEEK. THE

BEGINNING OF THE EXTENDED SHOULD BE FAIRLY QUIET WITH TEMPS

REMAINING ABOVE NORMAL FOR LATE MARCH. THERE WILL BE A LOW CHANCE

FOR SOME SHOWERS IN THE NORTH SAT NIGHT AND SUNDAY...WITH COOLER

TEMPS HERE. MODELS ARE COMING INTO GOOD AGREEMENT WITH A STRONG

SYSTEM EJECTING INTO THE NORTHERN PLAINS MONDAY NIGHT INTO WED.

THIS MAY BRING A ROUND OF ELEVATED THUNDERSTORMS TO THE REGION

MONDAY NIGHT WITH SFC BASED CONVECTION POSSIBLE TUE. BY TUE NIGHT

INTO WED...COLD AIR WILL WRAP INTO THE SYSTEM WITH PRECIP ENDING

AS SNOW IN THE NORTH. THIS SYSTEM WILL BEAR WATCHING FOR POTENTIAL

SEVERE WEATHER WITH THE GFS DEPICTING HIGH INSTABILITY/SHEAR EVEN

FOR SUMMER CONVECTION. IN ADDITION...SNOW AND WIND IS POSSIBLE ON

THE BACKSIDE OF SYSTEM WITH A VERY STRONG TEMP GRADIENT FROM SW TO

NW ACROSS THE FORECAST AREA.

There are substantial similarities in the synoptics right now and May 25th, 2008, by the way.

[Derek30]

Regardless of the magnitude of the severe threat, yet another abnormally far north threat for this time of year.

You got that right. I had my first storm activity this past Monday evening in southern Manitoba. Impressive lightning display and heavy rainfall.

I've heard rumblings around this forum regarding the northern tier having above average severe activity this spring and summer. Will be interesting to see how this pans out.

For me, it looks like next week's system will bring me some rain and maybe a few inches of wet snow on the backside.

Would be cool to get some thundersnow

[Thundersnow12]

There are substantial similarities in the synoptics right now and May 25th, 2008, by the way.

I don't know if I'd go that far..

[andyhb]

I don't know if I'd go that far..

Should've added "placement of the trough/SLP" after the synoptics part.

[andyhb]

18z GFS just went pretty nasty with dynamics aloft on Tuesday, although the surface temps and moisture are anomalously low compared to the 12z run, especially considering the 18z has a much stronger surface low.

ARX also highlighted the threat in their AFD:

THE WARM FRONT IS EXPECTED TO LIFT NORTH OF

THE REGION ON TUESDAY...LEAVING THE FORECAST AREA IN THE WARM SECTOR

AS A STRONG COLD FRONT APPROACHES FROM THE DAKOTAS. AFTERNOON 0-3 KM

MUCAPE VALUES ARE EXPECTED TO CLIMB TO AROUND 2100 J/KG BY LATE

TUESDAY AFTERNOON..WITH 0-6 KM BULK SHEAR VALUES OF 30 TO 35 KTS.

0-1 KM SHEAR VALUES ARE EXPECTED TO CLIMB TO AROUND 20 KTS. WILL

CONTINUE TO MONITOR FOR SEVERE THUNDERSTORM POTENTIAL WITH THIS

SYSTEM...ESPECIALLY IF MODEL TRENDS CONTINUE.

[Minnesota Meso]

I've been watching this the last 36 hrs or so, almost started the thread myself. This whole setup looks to be either very interesting or simply a rain event for the Upper Mississippi Valley with generic T-storms. IMO the big player here will be the pesky cut off upper low. Where will it exit the east coast?? To far north and the SE US ridge will move west towards the TX area and essentially cut off the low level moisture feed from the gulf, at little further south will delay the western move of the ridge and allow rich low level moisture to funnel north all the way to the Canadian border.

I'm Just a amateur weather nut or , if you will. So my question for the pro's is what do you think is more probable???

Just the same what a incredible March it is, historic warmth, with one severe event already in MN, and we are talking about another one?? Just one word comes to mind that I can post here, INSANE!!!

[andyhb]

I've been watching this the last 36 hrs or so, almost started the thread myself. This whole setup looks to be either very interesting or simply a rain event for the Upper Mississippi Valley with generic T-storms. IMO the big player here will be the pesky cut off upper low. Where will it exit the east coast?? To far north and the SE US ridge will move west towards the TX area and essentially cut off the low level moisture feed from the gulf, at little further south will delay the western move of the ridge and allow rich low level moisture to funnel north all the way to the Canadian border.

I'm Just a amateur weather nut or , if you will. So my question for the pro's is what do you think is more probable???

Just the same what a incredible March it is, historic warmth, with one severe event already in MN, and we are talking about another one?? Just one word comes to mind that I can post here, INSANE!!!

As this next trough digs on the west coast, it will likely shunt the ridge east, which will in turn force the cut-off eastward and off shore eventually, likely by around Day 4 or 5. You will then probably get at least a day and a half of return flow from the Gulf prior to the next system, which is still pretty much as juiced as it was prior to the system this week. Temperatures are still in the 50s and 60s behind this cut-off, which means once the ridge returns later this week, there will probably be plenty of warmth in front of this next short wave, which if we have the types of kinematics the 18z GFS and 12z Euro are suggesting, would probably mean trouble..

[cyclone77]

Getting a little too excited looking at some of these forecast soundings. Obviously a little early to look too closely at those, but I couldn't resist. Definitely an interesting feature to watch in the next several days...

[andyhb]

00z GFS has the closed low exiting the east coast by Day 4, that leaves 2-3 days of return flow out of a very warm Gulf for this system to work with.

Upper/mid level jet streak associated with it is much stronger at 114 than at the same time frame on the 12z/18z runs.

[baroclinic_instability]

This topic was started in the wrong thread. Plains/MN belongs in central/western.

[andyhb]

^{This is one of those times where I wish we had the good ole' consolidated C/W forum, since areas of the GL/OV forum are also likely to be included here...maybe a move to the general forum may be the best option?}

[baroclinic_instability]

^{This is one of those times where I wish we had the good ole' consolidated C/W forum, since areas of the GL/OV forum are also likely to be included here...maybe a move to the general forum may be the best option?}

The threat exists in both, so it is up to Hoosier how he wants the threat discussed in Lakes/OV since it may extend into that geographic region as well. Trust me...I am not a fan of having multiple discos either, but it is the way it has to be for now. Right now I don't believe the threat is big enough to be in the main disco atm.

[cyclone77]

Yeah this setup favors areas pretty close to where the dividing line is between the western/central and GL subs lie. Bound to happen from time to time. Personally I never really liked the split of the forums, but it is what it is. What I never understood is the need for all the divisions in the forums to begin with, as you usually click on threads you're interested in anyway which naturally excludes threads outside of your area of interest.

[baroclinic_instability]

Yeah this setup favors areas pretty close to where the dividing line is between the western/central and GL subs lie. Bound to happen from time to time. Personally I never really liked the split of the forums, but it is what it is. What I never understood is the need for all the divisions in the forums to begin with, as you usually click on threads you're interested in anyway which naturally excludes threads outside of your area of interest.

I agree to a point...severe weather is a different beast than winter weather in terms of who it attracts...and the large areas severe threats can cover. I would love to see one large "severe weather" forum.

[andyhb]

Impressive hodos on the 00z GFS between 138-150 hrs across MN, WI, IA and Northern IL...juxtaposed with upper 50s and 60s dews and temps in the 60s and 70s.

[Thundersnow12]

I agree to a point...severe weather is a different beast than winter weather in terms of who it attracts...and the large areas severe threats can cover. I would love to see one large "severe weather" forum.

Yes please.

[baroclinic_instability]

Yes please.

I have brought it up to the admins, but no decisions have been made at this point. Best thing you guys can do is lobby for what you want.

[cyclone77]

I agree to a point...severe weather is a different beast than winter weather in terms of who it attracts...and the large areas severe threats can cover. I would love to see one large "severe weather" forum.

Yeah that'd be nice. Since the subs have been divided up I have a tendency to check just the lakes sub from time to time. I need to spend more time in this sub as it usually has mutual interests to the lakes. Guess I'm just lazy that way lol.

[andyhb]

Mid level temps are <5 degrees at 700 mb and <-10 (mostly <-15) at 500 mb.

[tornadotony]

Yeah, to be frank having 3 or 4 different threads for one system is asinine (see 2 March).

[thewxmann]

Hate to go into specifics so early, but moisture depth/quality should be watched in subsequent runs.

P.S. We ought to do all severe threads in the Weather Forecasting/Discussion forum from here on out, IMO.

[Hoosier]

Let's stay with subforum threads for now. Someone can create one in the Lakes/OV subforum. This threat is still quite a few days away. Later on if still looks like an event that could have significant impacts in both subforums then we can move to the main forum.

Due to the overall success of the last main forum severe thread and the positive feedback that was received, it is something that we definitely want to do for higher level/multi forum threats.

[baroclinic_instability]

Yeah, to be frank having 3 or 4 different threads for one system is asinine (see 2 March).

Yes we are dealing with that. We are trying to push significant events to the main forum. It did finally happen with the March 2nd event, but it took a while for the disco to fully transition to that thread in the main forum. Maybe someday we will have a large severe weather forum...but right now that is only an idea.

[tornadotony]

The threat exists in both, so it is up to Hoosier how he wants the threat discussed in Lakes/OV since it may extend into that geographic region as well. Trust me...I am not a fan of having multiple discos either, but it is the way it has to be for now. Right now I don't believe the threat is big enough to be in the main disco atm.

Why not just move it to the general forum and have no threads in the subforums?

[cyclone77]

Why not just move it to the general forum and have no threads in the subforums?

Yeah that would work out pretty nicely I think. That would add a lot of quality discussion too from enthusiasts/mets outside of the impacted regions.

[baroclinic_instability]

Why not just move it to the general forum and have no threads in the subforums?

It certainly is an idea, but there is resistance to that. There is resistance to a severe weather forum as well. Honestly there is no perfect way to tackle the problem. The resistance to taking the discos out of the subregions is it takes away the local discos/observations that subregions tend to create.

[baroclinic_instability]

Yeah that would work out pretty nicely I think. That would add a lot of quality discussion too from enthusiasts/mets outside of the impacted regions.

Personally I think a lot like you...and this is due to the fact severe weather attracts a completely different crowd than winter weather discussions. This is undoubtedly a winter weather board...and it is no surprise the subregions don't work as well with severe weather discos. But yes, I hate having all the severe weather minds split among subregions or forcing them to choose which disco they want to take part in.