Saturday, March 21, 2009
Rain moving in Sunday.. more on the way Tuesday..
Models are coming in line that southern MB will be seeing two waves of precipitation starting tomorrow. On Sunday, a band of showers and possible thunderstorms will develop along the MB/SK border and progress eastward through the day, likely reaching Winnipeg and the Red River valley by late afternoon. Rainfall could be heavy at times, with amounts of 15-25 mm possible Sunday night over the Red River valley. This band of rain will move off by Monday morning, with little additional rainfall expected Monday into Monday evening. However another wave of precipitation is expected to move into southern MB overnight Monday into Tuesday as a storm system moves up over the Dakotas. This system is forecast to give another 15-25 mm of rain over southern MB, likely changing to snow over western MB Tuesday as colder air wraps on the backside of the storm. This colder air will likely change any lingering rain to snow over the Red River valley Tuesday night into Wednesday, with accumulations of 10 cm possible. All in all, it looks like a prolonged period of unsettled weather moving in between Sunday and Wednesday, with significant precipitation amounts that will elevate flooding concerns throughout southern MB. Stay tuned..
Posted by rob at 9:11 AM
Subscribe to: Post Comments (Atom)
Rob... so there is a chance that the embedded thunderstorms could make it to the Winnipeg area Sunday night>??ReplyDelete
Or will the thunderstorms turn to all rain by that time??
When they talk about "elevated" convection....and they talk about "surface based storms"....what would cause the storms to be one or the other????
The source region of the air parcels convecting or, in other words, the cause of the storms.ReplyDelete
If the air is originating at the surface because of free convection (overturning on a hot day) or a front or the like, then it's surface-based. If, like would happen in this case, the air parcels are coming from a layer above the surface (925 mb, 850 mb, thereabouts) with warm and moist air being forced to lift to its LFC, then this is considered elevated convection.
Models going crazy with QPF and convection for Sunday nite/Monday morning in S Manitoba. Although the LLJ will be a very impressive 65 kts... nose will be aimed at central/northern Manitoba. Will have to rely on embedded waves and broad isentropic lift to generate convection. I still suspect QPF may be a bit too high.ReplyDelete
Winter storm warnings out for northern and central AB/SK with a watch for N Manitoba. This is in region of strong 700 hPa thermal gradient. Good deformation type snow band likely to set up starting tonite.
Interesting to note the erosion of left over stratus from NE to SE... that dry easterly flow is trying to work its magic. Clearing line appears to be at Bird's Hill now. However, higher level clouds are advecting westwards at the same time.ReplyDelete
Excerpt from NWS Grand ForksReplyDelete
FOR SUNDAY/SUN NIGHT...A BAND OF SHOWERS AND EMBEDDED STORMS ARE
EXPECTED TO MOVE FROM WEST TO EAST THROUGH THE NIGHT. VERY STRONG
850MB MOISTURE TRANSPORT AND SOME INSTABILITY WITH SHOWALTERS
AROUND ZERO WILL ADD TO THE ELEVATED THUNDERSTORM THREAT.
PRECIPITABLE WATERS WILL ALSO RISE TO AROUND OR OVER 1
INCH...ALONG WITH SFC DEWPOINTS AT LEAST INTO THE 40S FOR MOST
AREAS BY SUNDAY EVENING. THIS RAIN AND WARM TEMPS WILL IMPACT THE
CURRENT FLOOD SITUATION...REFER TO THE HYDROLOGY SECTION OF THIS
AFD. TEMPS WILL BE TRICKY AND BE WARMEST IN THE SOUTH AND WHERE
THERE IS NO SNOW LEFT. WE HAVE ISSUED A FLOOD WATCH FOR THE VALLEY
AND POINTS WEST FOR SUNDAY NIGHT THROUGH MONDAY NIGHT...WITH
WILKIN/CLAY AND NORMAN COUNTY IN AN AREAL FLOOD WARNING WITH
NUMEROUS ROAD CLOSURES AND BREAKOUT OVERLAND FLOODING FROM RIVERS.
FOR MON/TUE...THE MOTHER LOW WILL SLOWLY MOVE INTO THE AREA AND
PRODUCE THE POTENTIAL FOR SIGNIFICANT PRECIPITATION. THE DEVILS
LAKE BASIN MAY CHANGE OVER TO SNOW LATE IN THE DAY TUE...BUT THE
ECMWF KEEPS IT ALL RAIN THROUGH THE DAY TUE...AND WILL CONTINUE
WITH RAIN THROUGH THE DAY. THIS SYSTEM IS VERY COMPLEX...AND A
SHIFT OF ONLY 50 MILES EAST OR WEST WILL PLAY A LARGE PART ON WHO
GETS HOW MUCH PRECIP AND WHAT THE FORM IS...STAY TUNED.
Download this...and listen...seems pretty dire!
I think Anonymous meant to try this out...just downloaded it!ReplyDelete
It does seem pretty serious!
Link does not work with mozilla.. have to use internet explorerReplyDelete
The rain showers that are forming in southern Manitoba right now is kind of a surprise!ReplyDelete
I did not expect any rain tonight!!!!
That band of rain moving through Sunday night will be coming down fast and heavy.. general amounts of 15-25 mm possible within 6 hours or so. That will likely cause drainage problems with our frozen ground. Watch out for major ponding of water for the Monday morning commute. Then a more general rain Tuesday, perhaps another 15-25 mm, but spread over a longer time period of 18 hours, before changing to wet snow Tuesday night. Such a scenario will challenge our drainage systems this upcoming week, and can lead to extensive basement flooding. A rainstorm at the end of March 2004 produced extensive basement flooding when we had 40-50 mm of rain within 24 hours on top of a 20 cm snowpack. Some communities had to declare local states of emergency due to extensive overland flooding.ReplyDelete
By the way, for those of you who have one, you may want to dust off those rain gauges and set them up tomorrow to monitor rainfall amounts this week. Feel free to post any amounts on my blog to keep everyone up to date on storm amounts.ReplyDelete
Showers in SW Manitoba don't surprise me... best low level moisture return was temporarily diverted to Saskatchewan. Those showers will likely break up as they encounter the dry easterly flow. Eventually the cloud line will push back to the northeast. When exactly is a trickier question.ReplyDelete
Another question for Rob or Dave. Does EC have access to forecasting tools such as isentropic analysis (X-section of isentropic and momentum surfaces) or Q vector analysis? Picking out areas of frontogenetic forcing, CSI, LLJ would be a lot easier...
Why does the National weather service radar have 2 different scales???ReplyDelete
Looking at it tonight it show precip. that is at the "top" of the scale!
Other times they switch the scale to something you would see on a more regular occurence!
The "top of the scale" radar image is using a setting known as "clear air mode". It basically is at an ultra sensitive setting to highlight moisture fields and boundaries in the lowest levels of the atmosphere when pcpn is not occurring (hence the name). The setting is so sensitive it can detect bugs, birds and dust. Radar will usually switch to normal precip mode when precipitation is approaching or within radar range.
Here is my breakdown (numbers for RRV and area):ReplyDelete
GFS: 45 to 50mm
NAM: 50 to 55mm
ENS: 25 to 35mm * High Probability
I have figured that averaging as many models as you can find will often yield a good number. Right now I think 30 to 50mm of precipitation is a reasonable estimate for the RRV between Winnipeg and Fargo. I would expect some areas to see higher amounts, and others lower amounts, especially because of the potential for convective cells. The ENS (Ensemble) gives a high probability (>80%) chance of more than 25mm of precipitation over the RRV. The ensemble tends fairly conservative, in terms of its predictions, so I would expect that its numbers are a good base to build from.
It looks like the vast majority of the precipitation will be rain, however the potential remains for heavy snow on the backside of this system, should the precipitation change over quickly.
Looking at the radar this morning I almost fell out of my chair!ReplyDelete
There is the biggest thunderstorm that i have ever seen in Southern Manitoba......oh.....ya the radar is on the "snow" mode.....
Yeah, snow mode will exaggerate radar returns with rain or thunderstorms. Hopefully they can switch the radar to rain mode for this upcoming event. Nonetheless, impressive convection for this time of year with thunderstorm cells of 40-45K feet this morning over SW MB! Pretty good lightning showing up with hail possible.ReplyDelete
There's a possibility we may see some thunder tonight in the RRV as upper trough approaches with good low level jet. Currently, EC forecasting 10-15 mm for Winnipeg and much of the RRV tonight although I wouldn't be surprised to see amounts of 15-25 mm due to convective input. Watch out for major ponding of water tomorrow morning.
We then get a break Monday before the next wave moves in Monday night into Tuesday. Looks like another 10-20 mm for most areas Tuesday, except local 20-30 mm closer to the US border and over the RRV. GFS still indicating a change to snow for the RRV as early as Tuesday morning, while the GLB is indicating more rain for us as the Dakota low continues to feed warmer air aloft from the southeast. That may in fact lead to a narrow but significant band of freezing rain along western portions of the RRV where the air aloft is warm enough for rain, but northerly winds in the low levels draw in subfreezing air at the surface.
GLB then slows down upper low over Lake of the Woods through Thursday now bringing accumulating snow to RRV both Wednesday and Thursday.. possibly giving 10-20 cm over those 2 days. Blechhh.. what a messy week coming up, and more importantly, a more serious situation developing for flooding concerns throughout southern MB.. not only RRV. Given the prolonged duration of this event and the precipitation amounts involved, I think there's a growing possibility of extensive overland flooding this week across southern MB owing to our frozen ground and melting snowpack.
Gotta love the forecast for Rapid City, SD.. 18C today, blizzard tomorrow giving 30-45 cm of snow by Tuesday along with wind gusts to 100 km/h!ReplyDelete
Looks like south western Manitoba will be getting a whole lot of rain this afternoon!ReplyDelete
The radar is starting to light up like a Christmas tree!
Look....all those thunderstorms starting to form south of the border!
Brandon already reporting a thunderstorm as of 9:00 AM
There is a severe thunderstorm warning out for Bottineau, ND. 100km/h straight-line winds are possible. The best part...It is +1 in Bottineau.ReplyDelete
One of the most complex and interesting storms I have every followed, I think we will all have learned some important lessons by this time next week.
Question is will those severe thunderstorms make it over the border and affect southern Manitoba????ReplyDelete
Oh....very interesting system indeed!
I did not think it would be possible to get even a regular thunderstorm when it is so cold!
Damaging 100 km/h winds confirmed at the Minot air force base!ReplyDelete
Severe thunderstorm warning, blizzard watch, flood watch all at the same time for them!!!
General rainfall amounts of 12-17 mm this morning northwest of Brandon according to CWB network.. with more on the way. Some sites recording wind gusts of 50-60 km/h.ReplyDelete
Daniel(s?) (How many different Daniels are on here, anyhow? :))ReplyDelete
The thunderstorms are forming because of a good feed of heat and moisture off the surface coupled with steep mid-level lapse rates. If you look at the 12Z Bismarck sounding you'll see exactly that, and if you force a parcel of air (say, by lifting it over the warm front) you can get 900 j/kg of CAPE. In fact, SPC mesoanalysis has over 1000 j/kg over the region now.
As for the question about isentropic analysis, well, not to the extent NWS has. EC's is very rudimentary but we make do.
Yeah.. what's up with so many Dan and Daniel's... have of us posting here have that name lol.ReplyDelete
The interesting weather continues. Impressive convection as has been noted. Whole complex looks fairly progressive.. however the potential for cells building back into the LLJ will have to be monitored. This would lead to training of cells over the same areas (propagation vector and advection vector canceling each other out).
Nice clear slot forming over SE Manitoba... this could lead to further destabilization and will have to be watched.
LLJ shifts east tonite and RRV valley will be under the gun. 70 kts screaming right off the gulf.
It should be able to tap 850 hPa dewpoints between 10 to 12 C over the central plains.. amazing. Surface warm front looks to stay south.. but with all that instability and lift from upper wave... another round of convection is likely.
Further to the point about elevated convection.. that is why looking at MUCAPE (Most Unstable CAPE) is more useful than looking at SBCAPE (Surface Base CAPE) or MLCAPE (Mixed Layer CAPE). MUCAPE is calculated by lifting parcels from various pressure levels and finding the maximum instability.ReplyDelete
It is very unfortunate that EC does not have access to some of those tools. EC is being handicapped by having to use older forecasting techniques... NWS has a big advantage there. I cannot believe our government will not better fund and equip our weather service. *end of rant*
Flood warning issued for all of northern Dakota!ReplyDelete
1-2 inches of rain will fall with embedded convection will really drive those totals through the roof!
Looks like southwestern Manitoba is really getting pummeled today!
If what is happening out there today is any indication of what it will be like tonight in the RRV then you better get the rubber boots ready folks!!!!
Severe Thunderstorm Watch issued for parts of SW Manitoba.ReplyDelete
Thats the earliest Severe Thunderstorm Watch I've ever noticed issued for anywhere in Manitoba, in terms of the fact that it is only March 22.
Severe thunderstorm watch mainly for winds.. although I think the greater impact will be from rain. According to CWB mesonet, there is an area of rainfall between 25-35 mm already through the Hartney/Rossburn/Shoal Lake areas. These are unofficial amounts, but they look reasonable given the radar returns. That must be leading to some local flooding in that area. Here in Charleswood, many residential ditches are at bank full or overflowing onto properties.. and this is before we have any rain! I have a feeling there will be extensive overland flooding in our area by Wednesday with flooded basements and local road closures.ReplyDelete
I'd have to agree with the overland flooding idea.ReplyDelete
Here in the SE area of the city ditches all over the area are filled to the top and overflowing onto sidewalks in some areas.
Around Bishop Grandin Blvd the ditches are so full they're flooding up onto the gravel shoulders in places. Any more rain/snow/any precipitation will only cause these levels to rise and I can very well see some areas being somewhat flooded, along with some underpasses around the city too.
+23 in Rapid City today, +1 tomorrow with 30cm + of snow...and we thought Manitoba's weather was variable.ReplyDelete
looks like a nice clear break about come thru Winnipeg. This is ahead of convective blow off from storms developing in eastern N Dakota. Here we go...ReplyDelete
On the West Bank RR facing SE to BG Bridge.. Shore channel 15 feet of open water (is home to several new geese. I don't think that storm sewer they are rushing down Chevrier/Crescent drive will be there on time.ReplyDelete
Assume the Geese have used those south winds to get here early
Temperatures a lot warmer down in Grand Forks and Fargo... even though they are also north of the warm front.ReplyDelete
Pool of higher dewpoints down there aswell.. approx 7 C. In Winnipeg we are still getting dried out by the SE flow with a dewpoint of 1 C.
If surface dewpoints do not come much.. we will be dealing with a lot of evaporative cooling... Rob, what do you think temps will be like when that convection rolls thru?
I suspect those higher dewpoints will advect in this evening as the showers approach, and the low levels moisten up from the south. Dewpoints getting up to the +10C mark now over southwest ND.. quite the dryline between RAP (-5C) and PIR (+10C)ReplyDelete
Some impressive rainfall totals over western MB today from CWB mesonet..ReplyDelete
Rivers....... 45 mm
Rossburn..... 40 mm
Hamiota...... 38 mm
Shoal Lake... 35 mm
Minnedosa.... 26 mm
Another unofficial station in Strathclair is reporting 42 mm today. These are significant amounts given they fell within 12 hours over frozen ground and a heavy snowpack. And more on the way tomorrow..
Oh boy.... look at the thunderstorms erupting in the dry slot in far western North Dakota!ReplyDelete
Is this March or May????
Also note the heavy convection heading into the Grand forks region!!!
Just looking at the conditions in western ND (+13 temp, +9 DP), weak severe thunderstorms certainly aren't as unusual as severe storms at +1.ReplyDelete
I wish I could get an aerial view of some of these flood(ed/ing) areas.