lakeville weather journal

As noted this AM, impressive moisture stream continues to dominate the weather pattern. Looking at 00Z model runs tonight, there is no sign of relief either, as we are stuck in a very wet pattern for the next seven days minimum. GFS paints dewpts no lower than 55 through mid-next week! Viewing other synoptics: currently weak--but evident from wshft--sfc boundary is currently KINL-KBJI-KATY and back into srn SD before running into multiple outflow signatures on the sfc plots...due to impressive MCS and squall running across all of NE. Matchup with water vapor img shows cyclogenesis rolling off the CO front range...a feature progged slightly better by 00Z GFS run. At around 1000mb, this will be the focus of the energy from a very elongated and negatively-tilted upper trough about to cut off into a stacked low by late tomorrow.

Synoptic features tomorrow show the low over KATY at noon (GFS based...NAM lost consistency from 12Z-00Z runs). Frontal boundary will begin gradual push east as upper low cuts off and cold pool deepens over the Dakotas. Ahead of the front and the low, MN will experience dewpoints pushing 70, and enough radiant dirurnal heating for CAPE values of 1500J/kg plus. Big question is if init is frontal lifting or upper dynamics...jet streak progged to wrap the upper low with max couplet joining the LLJ over SW MN around 20Z. Theta-E ridging not as prevelant from weaker frontal dynamics. This may change, however, with a katabatic effect off the Couteau des Prairies...and only later models (maybe a mid-moring RUC run) will have this feature tagged if it crops up.

As cold pool bulges southeasterly, front will move from southwest to northeast as main 990 low remains anchored near KTVF. Convective development will init along and ahead of front overnight Wed into Thurs AM. HPC prog charts occlud the front Thurs AM over NoDak, however I think convective dynamics tomorrow may have a different push to the synoptics...only time will tell. For now, concentrating on 'recent norms' and some eval of MOS, best forecasted init looks like the 20Z timeframe tomorrow in sw MN. Good potential for MCS development and severe storms does exist. Will also keep temps bumped up from MOS, as they have consistently run (as they do) cooler...

Wednesday...Mostly cloudy, muggy, and warm. High of 82. 60% chance of thunderstorms after 4pm, some could be severe. Low 62. South winds 10-15 mph.
Thursday...AM showers and thunderstorms give way to partly cloudy skies. High 75. Southwest wind 10-15 mph. 30% chance of a shower or thunderstorm after 6pm. Low 55.
Friday...Mostly cloudy. High 76. 40% chance of a shower or thunderstorm. Low 57.

Posted by pierre at 10:50 PM | Permalink

Very a-typical pattern this week to analyze synopically. Currently, surface based low spinning over KGFK with a secondary downstream MCS/outflow borne low over Sioux Narrows, Ont. From these cyclones comes a very slight boundary along the MN/Dak borders. Ahead of the surface front, strong southerly flow from Gulf raised dewpoints dramatically overnight. Most stations now reporting low 60's from KCWA westward this morning at 11Z. Upper trough will make its last move before cutting off from the polar jet today, advancing the front only slightly and causing enough of a ripple effect to trigger late-day convection.

After this happens, models show the trough cutting off at H50 and upwards initially, and parking over the KRAP area by late tomorrow. Good news - warm/mild conditions will persist through the week. Bad news (or maybe good news for some) rainy conditions will persist as well for our area as we remain on the eastern side of the low. NAM has the system deepening to the H70-H85 levels by the weekend. GFS long-range shows the cutoff and stacked low moving off to the Great Lakes by late Saturday, and a resurgence of the upper jet nosing in by Monday.

Over the period, challenge will be incorporating mesoanalysis with the synoptic, and formulating better if and when statements on precip and max temps. For now, we are going to tweak the MOS ensembles a bit to give you a quick 3-day forecast:

Tuesday...Mostly cloudy, muggy, and warm. High 82. Rain moves in after 4pm. Chance of rain and thunder 50%. Low 60. Wind south 5-10mph.
Wednesday...Mostly cloudy. Still humid and warm. High 76. 40% chance of rain. Low 57. Wind south-southwest 5-10.
Thursday...Mostly cloudy. High 72. 30% chance of rain. Low 55.

Posted by pierre at 6:21 AM | Permalink

I hate to gloat, but I am extremely proud of my 00Z analysis last night. WFO's and even the SPC had initially discounted the modeling of CAPEs and Li's...except when things started to really pop - right around 1400CDT *weird...thats what I said would happen*.

Ok, enough of that...MCS/line that did form along the shortwave/frontal boundary has pushed into WI now (2200CDT). Dissipation of the frontal boundary is prevalent as winds are calm behind the storms, and there has been no real appreciative temp or moisture change in the atmosphere. Dewpoints remain elevated...still at pre-convection values of mid-lower 60's. Looking at MADIS plot, definitive frontal boundary is showing in western MN, from BJI-AXN-MML. Temps are beginning to drop a bit, but telltale wind shift and dewpoint drops are indicated by the reports. NAM seems to have best handle on initialization, as well as placement of the frontal feature for the near-term forecast period. The model progs the front to begin some meager motion eastward overnight. LLJ still progged to have one last surge from the south in advance of the front, and I think timing looks good on that being the impetus for TSRA redevelopment sometime after 07Z...with initiation on the nose of the LLJ, in south-central MN. Expect another line of activity, more showery in nature, to fill in from MKT-STC-GPZ into the morning commute. Some more stalling will occur as the front tries to push further into WI, bringing into play the possibility of training along, and just behind, the boundary as the southerly flow continues to push along and over the front. NAM targets some precip bullseyes over the ern tier of MN counties pushing the 1.5" mark by 18Z. Sunrise will also aid slight elevated redev.

After 18Z, however, things will rapidly change. Expect cool inflow behind the CFP from the northwest...dynamically backfilling, as the pressure gradient will simply not be there to warrant anything over 10kts. So, some partial drying will happen late tomorrow and into the first part of Friday. Then the holiday weekend progs got a bit more interesting...12ZGFS run paints a low to slide down the Canadian and Montana front range tomorrow, over the Powder River basin Friday, and into the Sioux Empire by mid-Saturday. Upper level dynamics are of greater concern for the system...jet goes zonal after tomorrow, and upper low associated with this next wave is progged to become negatively tilted, and somewhat cut off by Saturday. Also, GFS paints a bit of divergence in the jet as the mid- and lower-level flows in advance of the system return to a south-southwesterly orientation. Future model runs will need to resolve the scenario better...right now it either looks to be a cold-pool rainmaker, or a developing severe weather threat, or possibly both depending where you are! Right now, however, I have confidence of a rain event late Saturday. Sunday and Memorial Day look to be tamer, drier, and comfortable.

Thursday...showers and thunderstorms likely before noon. High 66. Low 48. Southwest wind turning northwest 5-10 mph. Rain chance 60%.
Friday...Partly cloudy and comfortable. High 74. East wind 5 mph. Low 50.
Saturday...Mostly cloudy. Thunderstorms develop in the afternoon. High 72. Low 45.
Sunday...Mostly cloudy. High 72. Low 46.
Memorial Day...Sunny. High 74. Low 54.

Posted by pierre at 9:46 PM | Permalink

00Z model run tonight did shed some more light on specs for both short- and long-term forecasting. Short term synopsis remained unchanged. Elements I was looking for to confirm any severe weather potential tomorrow did show up...particularly CAPE values of 1000-1500J/kg tomorrow afternoon across the sern 1/3 of MN. Also, vert motion max's progged through the mid levels in same locales and Li's from 2-4 riding a nice moisture plume through the entire day would make one think we may have a rough Wednesday afternoon...and we just may. The question is initiation. Very mature squall/MCS line attm in Ern Dakotas will spread debris and remnants eastward overnight. Extent will be deciding factor for tomorrows weather day. My bet is for sufficient breakup and clearing to give us a decent shot at diurnal heating. With a still strong southerly LLJ and the progged vert motion, I think the CAP will not form. Expect initiation along a BJI-AXN line initially, in area of H70 convergent flow...let's say 18Z and thereafter. Secondary init will be off a shortwave impluse ejecting ahead of the chief and resident longwave. This will cause forcing in the max CAPE between 20-22Z and from STC-ULM. Mean storm motion from 220, as has been for this storm system.

Short wave will run east and bring MCS/squall with it overnight Wed, and one last surge of the southern LLJ will re-prime the atmosphere...a feature very pronounced by both NAM and GFS. Expect a "final round" of storms Thurs AM, and finally pushing through with the long wave CFP late Thurs afternoon. Bulk of energy will translate into an intense mid-upper low that will park south of Hudson Bay. Friday into Saturday, GFS ensemble points to another shortwave from Alberta that will ride a zonal jet off the MT front ranges. Powered by a cool fetch, another rainmaker will run a 50/50 chance of rain Saturday PM. Still a bit out for certain yet, but it looks like a wet start to the holiday weekend. Cooler, yes, but not cold. Here you go...including a peek at the weekend!

Wednesday...Partly Cloudy. 60% Chance of Thunderstorms, some could be heavy to severe, mainly after 2pm. High 76. S winds 15-20 mph. Mostly cloudy after dark, low 52.
Thursday...Mostly Cloudy. 60% Chance of Thunderstorms before noon. High 72. Clearing skies and less humid after dark. Low 47.
Friday...Partly cloudy. High 68. Northwest wind 5-10. Low 48.
Saturday...Chance of thunderstorms. High 72. Low 50.
Sunday...Mostly cloudy. High 58. Low 42.
Memorial Day...Partly Cloudy. High 62. Low 45.

Posted by pierre at 12:40 AM | Permalink

Today's 12Z model runs are running in a dead heat...so the forecast certainty is solidifying nicely in the near term period. Last 48 hours has seen an impressive southerly flow set up camp in the region. H70 LLJ with max cores of 60kts have been streaming TX cT and entrance-tapped guld moisture to the upper Mississippi River valley. The cores are deep-running, and surface winds have seen 20-30kt sustained conditions with gusts well over 40-50kts in some areas where downmixing has been most prevalent. Main energy trigger has been long wave trough now running from Great Slave Lake in the NWT to the Four Corners. Progs have this feature digging even further south than originally expected, spelling out a delay of CFP from the associated sfc front now draped across the James River Valley in the Dakotas.

Now (23Z on the 22nd) several instability showers have sprouted in the warm sector dominating the North Star State. TCU's visible on GEOS and out the window all quads here in Lakeville. Deck of StratoCu and Stratus also has built into the mid-level. Due to minor low level capping, along with the swift southerly flow, these are rainmakers, but not much else attm. Progs show some diminished strength in the LLJ core after 00Z, and we should see development curb as a result. However, both models prog the H70 jet to reorganize in earnest, especially after the 06Z window, compelled by rapid mid-level cyclogenesis over srn SK. Secondary LLJ max also progged from NE through IA for strengthening over the same period. Models have somewhat of a different view of "what happens next". NAM has more confidence in morning TSRA and remnants keeping instability at bay through tomorrow, whereas GFS paints a more tame AM and a PM period with more convective potential. 00Z model runs will have to resolve this disagreement, as well as questions of severe potentials. SPC now has us back under the slight risk for tomorrow. Soundings forecast vertical shear along the front as it slowly moves into wrn MN. Hopes are 00Z model will incorporate a better ensemble to either support or deny the threat, as the current 12Z run does not do much more than confirm what we already have - warm humid, windy, and somewhat wet.

I will plan on an update after the 00Z models are accessible....late tonight. Also, a look at the holiday weekend forecast. Short term forecast...Mostly cloudy 40% chance of a stray shower or thunderstorm tonight. Low 56. Tomorrow AM, 50% chance of showers and thunderstorms, mostly cloudy, temps in the 70's.

Posted by pierre at 5:51 PM | Permalink

As the seasons continue to shift, the models are finally looking towards a promise of instability and precipitation that is more characteristic of the month. Weekend is ending on a mainly cloudy note...stratus deck riding on a cool low level adevection push from Lake Superior moved in overnight, plunging the low here at Lakeville to 40. Surface front responsible for keeping yesterday's 85°F heat at bay overnight has started moving back NE over the southwestern part of the state after noon today. GFS is much more aggressive with this feature, accenting the WAA and publishing max surface temps for the metro well into mid-70's in MOS. This has been stymied by the st deck and a few splash-and-dash showers that have sprouted late this afternoon across the area. As of 15Z, 990-1000mb low cirulating around the Powder River basin of WY, and its extent of eastern progress was main key to placement of the aforementioned front. Models have struggled (as they always do with the badland lows) with placement, depth, and effect of this low. Current data plots are now showing definitve troughing over the western Dakota badlands, with some central circulation over the Black Hills. The sat img and UDX 88D img confirm the central pressure defecit, coupled with current LLJ position fired off some +TSRA just off the Hills. Looking at the 00Z and then again 12Z model runs today, I have to toss off NAM...it just never pinpointed these features, whereas the GFS - especially in the 12Z run - is almost dead-center.

This follows guidance used by the local NWS-WFO's as well, and looking ahead on the GFS we can start to piece together the outlook for the next 72-120hrs with a little more certainty. As the Black Hills-Powder River low continues to deepen over the next 24 hrs, pressure gradient will intensify over our area as a southerly LLJ accelerates overnight and into Monday, streaming TX heat and Gulf moisture into the region. By noon tomorrow, it should be breezy and much warmer as the WAA takes over. Convection will most likely fire on the nose of the LLJ, which looks to hook up with the ULJ in a couplet near JMS-FAR by mid-tuesday. ABR and MPX WFO's are looking at these features with some certainty of a MCS or at least a training-type squall that moves out of the James River valley and into wrn MN by late tuesday-early wednesday. After that round, however, we are all scratching our heads about the main longwave upper trough, and associated cold front to roll off the front range in the wake. Upper winds will be the definitive ingregient for Wednesday...any veering off of the coupled structure will spell severe potential. A more agressive couplet could either push the system through faster, or just create more instability for rainmakers. One GFS element having some bearing is the prog of PWATs and TD's acrs the area. 1.5" to 1.75" pot's acrs the Dakotas were remaked as abv climatological norm for this time of yr. That same area of moisture will be backed in earnest by lusher, greener fields in MN. TD progs show us in a mid-60's range, against max heating of only mid-upper 70's for Wednesday. Shld the front be pushing acrs the ern Dakotas by 00Z/24th, we could see some heavy rains Wednesday night.

Tonight...Partly Cloudy, 30% chance of a stray shower. Low 52. Southeast wind 5-10mph.
Monday...Sunny. Warm and breezy. High of 83. South wind 15-20mph. Low 70.
Tuesday...Partly Cloudy and humid. High 85. Chance of thunderstorms after 4pm. Low 72.
Wednesday...Mostly Cloudy, but warm and still humid. High 76. Good chance of thunderstorms.

Posted by pierre at 5:00 PM | Permalink

Still working our way closer to MN fishing opener forecast finalization. Grids have shifted indeciseively for precip chances over the last 36 hours, however some alignment between models has begun to fall in place for Sat-Sun periods. First, a current synopsis: 0900CDT Thurs, weak cold front clearly defined by sfc wind elements on MADIS, running from Lake of the Woods, SSW to KFFM, to KATY, and then trailing back through SoDak. Really no pressure gradient along the CFB, but Canadian (AB) high pressure at fault for the boundary will move in quickly behind after passage today, causing winds to pick up quite a bit. Expect CFP at 19-20Z, with wind escalating somewhere around drive time.

Model focus then turns a watchful eye towards Fri-Sun period and precip/clds/overall synoptics to affect fishing opener. Polar jet remains zonal, with the max streak over western GL's for period. Central MN is also under main jet core, but not at a point where instability is too much of an issue. With cP high dominating through period...Albertan high entering region tonight will get reinforced by another area of high pressure sliding off Hudson's Bay, and setting up over GL's by end of period. Surface-based temps will moderate some after cfp today, but will quickly rebound as high pressure gradients subside. Dewpoints also remain moderate despite the cP moving in, thanks to some moisture retention from springmelt/greenup north of the border, with ensemble values never dropping below upper 40's/lower 50's.

General garden-variety precip chances will remain in the forecast grids from the NWS-WFO's, and I think they are merited at this point. We are talking 20-30% chc's tops here, and since the jet max is really farther north, Lakeville pops are negligible. Srn MN will remain dry. Due to the outlying possibility of surface-based advection triggering some splash-and-dash showers or isolated TSRA, but only after daytime heating max, close to 00Z Sun and 00Z Mon. As I finish off this entry, tem at 0930CDT is now 75. Today is going to get very warm in advance of the front!

Thursday...Mostly sunny, muggy, warm. High 87, calm winds turning WNW this afternoon 5-10mph. Clear tonight, low temp 54.
Friday...Clear. High 82. NNE wind 5-8 mph. Low 52.
Saturday...Clear skies turn partly cloudy. High 75. Light wind shifting SE through daytime hours. Very slight chance of passing shower or isolated thunder after 6pm. Low 55.
Mother's Day Preview...Mostly sunny, High 82.

Posted by pierre at 9:30 AM | Permalink

Well, it has been yet again another long hiatus from the weather journal. However, due to proddings from some friends and the advent of the 2007 MN Fishing Opener this weekend, it was time to get back into the swing of things.

The area has seen some unsettled weather over the last 72 hours, and presently the system has started to budge eastward as the omega block weakens its stance a bit on the Atlantic seaboard. After the frontal boundary pushes east of the area, temps and dewpoints are progged by both the GFS and NAM to remain moderate. This will keep humidity levels high, and will make the mid-week feel more June-like. The jet stream in the 48-84 hour periods is very zonal, riding the USA-CAN border. A slight dip post 120 hrs has been hinted in the GFS and EMCWF progs, but we are still far out for that to amount to any synoptic clues for more active weather approaching the weekend.

As a result, we are looking at a tame, warmer, and pleasant mid-late week forecast. Here is the three-day outlook for Lakeville:

Tuesday...Partly Cloudy, High 78. Nearly calm wind turning west 5 mph by sunset. Low 57.
Wednesday...Mostly Sunny. High 82. West wind 5-8 mph. Low 60.
Thursday...Clear. High 82. Low 58.

Posted by pierre at 4:48 PM | Permalink