lakeville weather journal

Models this AM are now showing a trend of stability on the short-term forecast. A couple of things for moderation from the last entry:

1) Trough is deepening over the Columbia River basin as I write...GFS has good focus on features and movement so I will lean more towards it for the next 24-72 hrs.

2) Low level flow has shifted gently to the SE this AM. DP's were already high as a moist pool of air shifted over us early this morning from NW MN, and now RUC and GFS agree on an intensifying LLJ max over the Dakotas moving east through the short term, increasing our warmth and moistiure even more.

3) GFS paints a slight ripple at H50 around 00Z this evening that may trigger some cloudiness, but too late for convection. This ripple, however preeceeds the big story...the longwave approaching from the Rockies, and on the doorstep Friday. I will match common thought from other local WFO's and raise POPs on Friday night a bit.

4) The GFS cuts off the low over MN, as mentioned before...but right now model has no real bearing on true precipitation genesis for the event...mainly because frontal passage timing is still a real unknown. The main certainty will be temps associated with the low and the cold front...NW MN gets tagged with some unseasonably cool temps (upper 40's for highs) while the GFS MOS for KLVN show X-temp readings of mid-upper 70's. This would possibly mean that the state will be (for the period Sat-Mon) split on separate sectors of the low and the front. However, I have a hard time believing that will last long...and to point, ETA shoves the low and CFP off by late Sunday.

So...for now, the update for the Labor Day Weekend forecast:

TODAY... Sunny turning Partly Cloudy by late afternoon. High 82. Light winds from the South. Low 62.

SATURDAY thru LABOR DAY... Partly to Mostly Cloudy. 30% chance of rain. Highs in the mid-60's, lows in the low 50s.

Posted by pierre at 11:14 AM | Permalink

The last week of summer vacation for many began wet and dreary this morning as an upper level disturbance kicked off some light rain showers and keep us overcast throughout the day. As we look ahead this week, a complex forecast is in store...but nothing earth shattering.

As the upper-level low and associated cold front passes through in the early AM hours, a nice fetch of drier air will push in from Manitoba...however recent rains in SE MN will keep the atmosphere moist enough to entertain a very slight chance of a splash-and-dash shower or thundershower over the river bluff country to our SE. This will only occur with dirunal heating sufficient enough for the build, and the ETA/NAM has CAPE values progged for the validity of this feature. For the balance of MN today thru most of Thursday, we are expecting beautiful blue skies. High pressure will expand out of Nebraska tomorrow and move east over the next 36 hours.

The next forecast challange comes of course into play for the Labor Day Weekend...and already the computers are progging the typical Murphy's Law forecast. Unfortunately, more than one model is making the prediction, making the reference hard to ignore. Currently a long wave trough developing off the Pac-NW coast is progged to deepen over the Continental Divide as the upper-mid level low strengthens over eastern MT Friday. Models...and particularly the GFS...has the low strengthen dramatically as it approaches the local area Saturday. In advance, southerly flow should increase, but the models are not painting anything exciting about it. This could be due to Ernesto focusing tropical energy over the Eastern Seaboard for the term.

The low gets cut off right over (you guessed it) MN, and some slowing is predicted as this occurs, spelling a dreary holiday weekend perhaps. Mid-level temps in the GFS for the FRI-SAT period show cold pooling in the low. On the positive side...it is way too early to give really strong creedence to the models. Some things I will be looking for over the next 72 hours: a shift in the prog of the southerly flow in advance of the holiday system; some better drying, and warmer temps with the near-term Manitoba flow; better placement of tropical features in the models for benchmarking (right now none of the models really tags up on the real-time analysis as well as GFS does so I want to give them a chance to catch up.)

So, here is the first glance at the week and weekend ahead for Lakeville...

TUESDAY... Cloudy in the morning, partial clearing by noon, and drier. 20% chance of a mid-late afternoon shower. High 82. NE wind 5 mph. Low 58.

SATURDAY thru LABOR DAY... Partly to Mostly Cloudy. 30% chance of rain. Highs in the mid-70's, lows in the low 60's.

Posted by pierre at 11:47 PM | Permalink

A wild night has indeed occured across the TC metro and SE MN. Tornadic event of what some are estimating at F2-F3 nature occured across Nicollet and LeSuer counties, and the storm responsible continued to show tornadic radar signatures until recently. Storm reports contine to stream in to the NWS, and the news tonight and tomorrow will be filled with the stories about today's weather...

...but we may not be "out of the woods" yet. The graphic above shows the radar picture as of this writing, as well as position of the weather system. Strong instability is now concentrated just east of the surface low over the Sioux Empire, and out across the plains of southwest MN, where temps AND dewpoints remain in the mid-70's. Meanwhile, the trough approaching the Red River Valley is keeping some elevated storms rolling into western and northern MN. There is a fair chance that we could see remnants of one or both of these convective areas spread into the TC metro sometime after midnight.

The cold front should swing through by 9am tomorrow, and bringing with it some drier air that will filter in by mid afternoon. Clearing drier skies will mean temps rebounding a bit into the 80's, for the weekend. Will hope to look at the models and write up a revised weekend forecast in the morning.

Posted by pierre at 9:03 PM | Permalink

...NOW... The severe weather situation for the Twin Cities metro continues to intensify and worsen. A cluster of tornadic cells (as confirmed by radar and storm spotters in Nicollet County around 1715CDT) has formed near the Mankato area, and is proceeding ENE in the warm sector, where surface bulk shear levels are highest. Additional cells are popping to the north and east of this area near Lakeville, but are in cooler airmass and not as explosive. Extreme hight falls are adding to continued instability, with local pressure falling rapidly through the afternoon.

A second line of storms has just cleared Stearns County, and has passed through STC southeasterly along I-94, and training down the frontal boundary. This line is beggining to bow a little, and shows evidence of strong wind and hail potential.

These two independant MCS clusters/lines are converging on the Metro Area at this time.

I have also circled in purple and area of genesis for further storm development tonight. This area of SW and SC MN is primed...temps have been in the upper 80's, and dewpoints in the mid-70's...and now the tornadic warm sector storms in Nicollet Co. show proof the cap has eroded.

Please stay tuned to local television and radio news stations for updates on warnings as the night progresses.

TORNADO WATCH UNTIL MIDNIGHT...FLASH FLOOD WATCH UNTIL 5AM

Posted by pierre at 5:36 PM | Permalink

The morning of a storm day kicked off with a line of severe thunderstorms passing through the Twin Cities, developing just after sunrise. The culprit remains a tropically moist, and extremely unstable airmass over the area interacting with a quasi-stationary frontal boundary draped across southern MN. The SPC issued WW 740 across the area for Severe Thunderstorms until 1600 CDT. As described above in the graphic, the threat for large hail and damaging winds continue as thunderstorms continue to develop this afternoon in the WW area.

The next focus of severe potential is the advancing short wave(s). The primary wave has crossed the SD Badlands, and now is providing punch for elevated convection in ND...a large tornadic cell has exploded near BIS, and this trend will continue along the wave as it trekks across Dakota. Meanwhile the warm sector will advance slowly ahead of the trough, bringing more potential for convection over southwest and into central MN through the evening, The self-evident triple-point will be co-located with a deepening sfc low now near PIR, and advancing to the Sioux Empire. As the warm sector has remained cloudless throughout the day, some capping may be in place. And we have seen that the majority of the development has been at the nose of the LLJ in the cool sector north of the front. As the whole system slides ESE, the area remains primed for further development.

MPX has just issued a Flash Flood Watch as well as I finish this post, and their afternoon forecast discussion should be out soon. Will update later on after new products and grids are complete.

THIS EVENING...Thunderstorms likely, with heavy rain and possibly severe with damaging winds and hail. Temps remain around 65. Chance of rain 80%.

FRIDAY...partly cloudy in the AM, and then clearing. High 82.

Posted by pierre at 2:15 PM | Permalink

Well, here it is...the start of the MN State Fair tomorrow and with it a Murphy's Law-typical forcast for thunderstorms. We certainly have seen a climate change over the last 24 hours...it is downright tropical in some areas, with dewpoints in the upper 60's and lower 70's. About 4am this morning the TC Metro was boomed from their beds to a strong line of thunderstorms that carried with it some soaking rain, frequent lighning, and wind. Those storms pushed out a nice boundary that "settled" along the stationary front that sits prominently about 20 miles south of here. NOAA's MESONET shows it nicely:

As does the MPX WSR-88D:

On the first image, I penciled in the boundary...which would be the red curved line with the humps. Notice the stations to the south of the line colored purplish-red (temps 80F+) and with winds from the south. North of the line the stations are hot pink (temps 70-79F) and winds from the northeast . I also pointed out the location of our station.

On the second image, the boundary is seen as a thin line of radar return extending from Hutchinson (HCD) through Lakeville (LVN) and southeast towards Stanton (SYN). I enclosed the area to look in a white elipse.

So what is the big deal?? Well, a couple of things. First, this demonstrates the fluid dynamics of the atmosphere in a very graphical way. Second, it means two very different airmasses are colliding with each other at the boundary. For the radar to pick it up like this is impressive.

Dewpoints will remain high as a short wave pushes down over the front range causing pressure to fall precipitously ahead of the system that could spawn more heavy storms tomorrow. The models have the low picked out commonly over the Great Plains trekking from central NE in the AM to over the Couteau des Praries by 3pm and then in central MN by 6pm. Instability will be hampered only by the possibility of atmospheric capping over southern MN. The morning cloud fields will tell the tale of possibility in this realm. Overall however, all evidence points to a significant rain event at the least, and possibly a severe wind and hail event at the most, with some tornadic potential more for SE MN. Here is a prelim forecast...hope to update throughout the day tomorrow as the situation warrants....

THURSDAY...Partly Cloudy and humid. 50% chance of thunderstorms after 4pm, some with heavy rain, hail, and damaging wind. East winds 5-10, turning southeast. High 84. Low 63. Rain ending after 10pm

SATURDAY...Partly Cloudy. High 78. Low 58.

Posted by pierre at 6:57 PM | Permalink

The past 5 days or so since my last entry has been dry, pleasant, and cooler. It would seem that autumnal weather is knocking on Minnesota's doorstep...and all the typical indicators are in place. Our average temp in August so far has dropped to 72F from 77F in July. Likewise, average relative humidity has dropped precipitously from 61% in July to 28% in August. We received almost all of our precipitation in the beggining of the month after the polar jet decided to slide back south from a north-of-60 position in the end of July. This shift coincided with the seasonal setup of the desert SW monsoon, and that feature remains in place as a driving force in US weather today.

As the monsoonal ridge remains anchored over AZ and NM, the polar jet remains in a relatively fixed zonal flow. The jet core remains hovering over our latitudes, and the impulses that do get translated into other than fair weather are typically spawned of lee-side of the Rockies troughs. So long that the monsoon contiunues in the SW, we will remain in this pattern.

One of the impulses is forming up right now, and a couple preceeding short waves have spun downstream to contend with. Both the NAM/ETA and the GFS paint a jet max between 500MB and 300MB that sweeps ENE'ward over MN, allowing the first short wave to develop convection and best forcing over NW MN later today. The second shortwave will propogate the jet core more easterly over the Dakotas and should develop an MCS that will persist into EC MN for tomorrow AM's commute.

The main lee wave that is generating our mid-week break from the norm is currently progged to move into the eastern Dakotas by late Thursday into Fri AM. Models aim precip bulleyes over central MN, with some ESE propogation through Fri. Your mid-to-end-of-week forecast for Lakeville...

TUESDAY...Mostly cloudy in the morning, turning partly cloudy in the afternoon. High 84 with light NE winds. Low 60.

THURSDAY...Partly cloudy and humid, 30% chance of showers and thunderstorms in the afternoon. Then a 50% chance of thunderstorms after dark. High 84, low 63.

Posted by pierre at 7:58 AM | Permalink

Over and over I say how spoiled we have been this summer. It only continues! This last week I took a hiatus from the journal with some other projects and distractions needing attention...and the weather was seasonal and tame to boot. As we enter one of the last weekends of summer for many, my eye turns again to a pretty textbook setup for convection. The pattern has shifted a bit more prospectively, as the GFS and NAM models both swung precip chances ahead in the calendar.

Currently, low level moisture is already in place throughout the region as cloud remnants from a Dakota MCS last night breezed in overnight and simmered in the dirunal sun. With dewpoints steady throughout the region in the low-mid 60's, and some pushing 70 out west, this will be the most attributable factor in atmospheric instability preceeding the cold front that is progged to sweep through early Monday AM. Indeed precipitable H2O values push over 2" in two pools according to the model ensemble - Northcentral through western MN late saturday PM and over the Sioux Empire for Sunday. Theta-E is on par with other dyn's, including a strengthening LLJ nosing up over the Sioux Empire. Upglide and advection promoted by the LLJ will tap the p-wat from FAR east towards the central lakes of MN, forcing convection Sat night.

One slight "anomoly" I spotted in the 12Z NAM run...3500 J/kg of CAPE plotted over the Couteau des Prairies at 00Z Sunday. CAPE values elsewhere were non-factors...The model favors the Couteau for convection genesis, so I have to wonder if this is just preferential treatment, or if an MCS will fire there as well as Central MN Sat night? One thing seems certain...should a well organized MCS fire over the Couteau, the cloud debris on Sunday may inhibit heavier pre-frontal convection later on Sunday, when the Twin Cities and Lakeville have the best shot at storms. The forthcoming model runs will have to revisit this. So my Lakeville Forecast for now...

FRIDAY NIGHT....scattered clouds, low 65. Fog possible in low areas after midnight. Light S wind to calm conditions.

SUNDAY....Muggy and warm, Partly Cloudy with high of 88. Thunderstorms develop after suppertime, move in towards sunset. Low 62. South wind 10-15 shifting to W and calming after dark.

Posted by pierre at 4:15 PM | Permalink

Forecasters scratched their heads this afternoon...the morning models showed impressive batch of potetntial for a classic sundown setup for severe weather to push across the Gopher State. Instead, residual clouds and some moderate capping has kept a steady layer of stratus buidling through the day and inhibiting daytime surface heating. That one ingredient was not present here, but over the Sioux Empire it was, and with the kick of the lee-wave trough over NE, folks between ONL and SUX are seeing stormy skies in the way of some rapid-fire convection.

Our surface front is still hanging out in Nodak, and has moved appreciably through mid-day. NOAA-MESONET data plots it out from Hallock, ND, through ABR, and SSW to just west of ONL. Satellite imagry confirms some cap weakening in the form of cumuliform buidling in west-central MN, about 120nm east of the front...typical. If the cap weakens some more, the ONL MCC should progress ENE, while new development rolls up east of the Couteau and fills-in squall line fashion. This is confirmed by precip potentials plotted in RUC runs. This places Lakeville under the weather by 2200-2300 CDT, with back building very possible from outflow. Rainfall potentential should push 1.5-2" as pWAT values remain high.

TONIGHT....Storms roll in after dark, some heavy with torrential rain and frequent lightning. STAY TUNED TO LOCAL NEWS RADIO OR TV FOR WEATHER ADVISORIES. Storms ending after 2am. Low 67.

MONDAY...Clear Skies and 84.

Posted by pierre at 6:09 PM | Permalink

Monsoon? Minnesota? Maybe? All these words fit, however monsoon and Minnesota don't seem to fit necessarily together. But the southwesterly monsoonal flow we are under the influence of is filling skies above with ingredients for another round of soaking showers and thunderstorms. As discussed yesterday, high pressure over the Lone Star State is serving as a pump for monsoonal moisture and heat from the desert southwest (incendentally, AZ and NM have been experiencing their seasonal monsoonal rains as well, with a meandering low pressure system that keeps drifring like an eddy between the Grand Canyon and the Rio Grande). The same moisture fueling the desert rains is riding a conveyor belt of air flow up to the Great Plains. Zonal (west-to-east) upper level flow skipping over the Rockies produced typical lee-side low pressure east of the Front Range and the instability kicked up a nice MCS that pushed from NE to IA ovenight. The southwestern low level flow spilled some of the MCS's precip northeastward into Lakeville this AM in the form of showers. This will only add to the ingredient batch for today/tonight as MN's turn for heavy convection returns...

A strong low pressure system is formed near Medicine Hat, AB last night and is digging in to the plains along the Canadian border. An associated surface cold front is in genesis, and by late afternoon the system will be on track for a positive orientation from TVF to ABR, as discuessed yesterday. Ahead of the front will be warm moist monsoonal air pooled up over MN. Couple the cyclonic/frontal system with a nice zonal jet max in the upper atmostphere, and the monsoonal jet max in the lower levels, converging somewhere between FAR and FFM this afternoon, and a nice profile triple-point sets up in the atmosphere. Models from the 12Z run are a little at odds on this feature, however, and timing is a little off as well. Later models and the RUC outputs may be able to clarify, as well as some RAOB data, but for now, local NWS WFO's are excited about supercells, and the SPC has issued a Public Info Statement regarding the potential.

My expectations are guarded for now, but a betting man will favor some typical behaviors...like storm intiation over the Couteau de Praries, and then firing along the frontal boundary from there. From 6pm to 10pm the Twin Cities will be under the gun, with storms arriving at or just after mature stage, some in supercells or possibly a bow MCS or even derecho. These are all possible with todays setup...especially since models are pointing out max CAPE and theta-E values right over us at 00Z.

Updates may be warranted later today as details evolve...but for now, here is your friendly neighborhood forecast:

SATURDAY... Partly Cloudy, High 87. SSE winds 10-15 mph. 70% chance of showers and thunderstorms after 6pm. Some may be heavy to severe with torrential rains and damaging winds or hail. STAY TUNED TO LOCAL NEWS RADIO OR TV FOR WEATHER ADVISORIES. Storms ending after midnight. Low 67.

SUNDAY...Partly Cloudy and a slight chance of a lingering shower in the AM, then clearing and sunny. High 82. West winds turning NNW 5-10 by afternoon. Low 60.

MONDAY...Clear Skies and 84.

Posted by pierre at 11:39 AM | Permalink

All in all, this summer has been bar-none the best of my memory, weather wise. Temps have been seasonal or better - always. Sunshine has been plentiful. For the first half of the summer, precip was on the borderline of "just enough" and "not enough". July was alltogether too dry, and now it looks as if August may be attempting a rebound.

Previously discussed system now working its way across the Rockies. Upper flow in zonal mode will carry it over the front ranges as lower level flow becomes monsoonal from the desert SW, aided by a relatively concentrated H5 high centered over TX. Warm frontal boundary will set up as theta-E and upglide of the monsoonal flow carries NE-ward into MN today. Front will genesis in central MN this afternoon, and will be the first focus of convection for northern MN areas this evening as folks head up to cabins on the 4th-to-last weekend of summer.

Low pressure center will sweep through SK and aid propogation of the cold front to a very familiar orientation -- the system will be positively tilted like the early week system that dumped 3-5" over much of central and southern MN. This means folks from Hinkley to Marshall and points east will get wet, but not until Saturday evening...enough ingredients in the NAM/ETA model to prove the need for severe chances (cape and impressive theta-E and vort maxes align ahead and paralell to the front by 00Z Sunday). NAM also paints some impressive precip max "bullseyes" over the same areas. Folks that saw the heaviest rains earlier this week may suffer deja vu on Saturday.

TODAY...Partly Cloudy, High 87. Humidity on the increase, so it will feel hotter...SSE winds 5-10 mph. Low 72

SATURDAY...Partly Cloudy, High 92. Showers and thunderstorms develop in earnest after supper. SE wind 10-15. Chance of rain 70%. Low 65.

SUNDAY...Clear and Sunny. High 84. Low 65.

Posted by pierre at 8:14 AM | Permalink

It has been a record-setting week:

7/31 - Record High Temp: 98.8F

7/31 - Warmest Night: 85.6F

7/30 - Record High Dewpoint: 78.3F

7/30 - Record Heat Index: 112.1F

8/2 - Record Rain in 1 hour: 1.28"

8/2 - Record Daily Rain: 2.12"

The storm total for yesterday and today was a record too...dumping 3.47" here at the station in about a 24-hour period. I have to say the setup was pretty classic...we were saturated with energy -- heat and water filled the air. It was literally a steam bath before the cold front pushed through. Today we are experiencing temps back into the mid-70's, and dewpoints in the mid-50's. Although this is still a bit muggy, it doesn't come close to the last five days. Tomorrow and Friday's northwesterly flow will filter in some drier air from Saskatchewan, and the flow will become zonal once again after a cold front and associated s/w shifts through the area Saturday...this could bring some more rain to the area. Better late than never!! This summer has been way too dry. We are still in an overall deficit, however, and hopefully yesterday's storms and the future climatological predictions of back-to-normal precip for August will hold true.

Posted by pierre at 6:15 PM | Permalink

Lakevilleweather.com is back up and running. We again aplogize for the inconvenience today.

Posted by pierre at 12:25 AM | Permalink