Friday, October 31, 2008

Ideal conditions for Halloween

It won't be quite as mild as yesterday's 17-20C weather, but conditions will still be ideal for trick or treaters this evening as a ridge of high pressure moves across southern MB today. Mainly clear skies are expected this evening with light winds and seasonable temperatures. After an afternoon high of +7C today, look for 6 pm temperatures around +4C dropping to +1C by 9 pm.  Best of all, there will be no snow or mud to track through as conditions have been dry for several days now.  Last year, after some rain and wet snow in the afternoon, conditions cleared for the evening with temperatures of +2C at 6 pm falling to -4C by 9 pm.  Two years ago, kids had to track through 10 cm of snow on the ground after a snowstorm on Oct 30th dumped 12 cm of snow in Winnipeg.  

Some Halloween weather highlights for Winnipeg since 1953..

Warmest Halloween…. 1999 - 6 pm temp: 15C
Coldest Halloween….1996 - 6 pm temp: -9C
Wettest Halloween… 2000 - 11.6 mm rain
Whitest Halloween.. 1971 - 18 cm snow on ground  
"Scariest" Halloween.. 1979
Rain changing to wet snow, Temp +1C, winds N 48 km/h 

Thursday, October 30, 2008

Nice finish to October

Some pleasant fall weather will finish up the month of October over southern MB with mainly sunny skies and nice temperatures. In fact, today Winnipeg will get into the mid teens as we get into a brief warm sector that brought some record temperatures in the low 20s across southwest MB and southern SK Wednesday. Cooler air moving in  later this afternoon will prevent Winnipeg from reaching the low 20s as happened further west. Temperatures will be a bit cooler on Friday with highs in the 7-10C range, but conditions should be ideal for trick or treaters Friday evening with mainly clear skies, light SE winds and temperatures around +5C.

Monday, October 27, 2008

Warming trend this week..cooler for Halloween

After a chilly night tonight (-6 to -9C most places) the weather will get a lot nicer this week as warmer air moves in from the west. Sunny skies and light southwest winds will boost temperatures to normal highs of +7C on Tuesday, then look for double digit highs of 10-13c for Wednesday and Thursday with sunshine and breezy conditions. Unfortunately a cold front will drop through southern MB late Thursday ushering a cooler airmass just in time for Halloween Friday. The good news is that it should be clear and dry for Halloween and winds should be dropping off by evening, with temperatures expected to be in the -2 to -5C range for Halloween evening. 

Thursday, October 23, 2008

Taste of winter on tap for Sunday

A strong cold front will push across southern MB late Saturday driving in the coldest airmass of the season so far Saturday night into Sunday across the area. The cold air will be ushered in by strong northwest winds gusting to 70 km/h, with locally higher gusts off the lakes.  Temperatures on Sunday will struggle to reach +3 or 4 degrees, and those gusty northwest winds will make it feel 5 to 10 degrees colder. Most areas in southern MB will likely wake up to see some snowflurries Sunday morning, but localities southeast of Lakes Manitoba and Winnipeg may see heavier bands of lake effect snow Saturday night into Sunday as those cold northwest winds sweep over the open lake waters.  Lake water - 850mb temperature differentials will be approaching 20C by Sunday morning, which is favourable for narrow bands of heavy lake effect snow. Note also that lake levels are running a little higher than normal right now, so northwest gales of 35 to 45 knots over the lakes may produce some shoreline erosion on the eastern shores of Lake Winnipeg and Lake Manitoba. Fortunately it appears this arctic blast will be short lived as lighter winds and moderating temperature are forecast for Monday and Tuesday.  

Monday, October 20, 2008

Nice week ahead.. Major cool down next week?

It should be a fairly nice week ahead across southern MB with generally near normal temperatures much of the week. There will be a band of rain moving across the Red River valley Tuesday night into Wednesday morning (perhaps 5 mm or so), but the rest of the week looks dry and seasonably mild with highs in the 10-13C by Friday or Saturday.  Unfortunately long range models are showing a significant outbreak of cold weather by Sunday the 26th which will likely result in below normal temperatures for the last week of October. In fact, if the models are right, the airmass will be cold enough for the first snowflurries of the year across much of southern MB, with the potential for snowsqualls off the MB lakes.  So be prepared for a chilly Halloween (yet again!), along with the possibility of some of the white stuff around.

Downtown Winnipeg still frost free

Although freezing temperatures have been recorded across most of southern MB by now, the growing season continues in downtown Winnipeg which has still to register a below freezing temperature so far this fall. The lowest temperature so far at the Forks weather station downtown has been 0.3C on Oct 17th.  This morning, while the temperature at Winnipeg airport dropped to a chilly low of -4.8C, the Forks station recorded a low of +1.5C, over 6 degrees warmer than the airport site.  This difference is due to a phenomenon known as the "urban heat island" effect, which basically keeps temperatures (especially nighttime temperatures) warmer in a downtown core compared to nearby rural areas which can lose heat to the environment more effectively. This prolongs the average growing season downtown by 2-4 weeks compared to the airport site. 


Sunday, October 12, 2008

Storm system brings rain and snow to southern Prairies

The storm system affecting the eastern Prairies continues to spread rain into southern MB this morning, which turns to snow across the border into Saskatchewan. Snow will continue to fall across much of southeast and southcentral SK today into tonight with snowfall totals of 10-20 cm possible by Monday, and locally up to 25 cm over higher elevations south of Moose Jaw.

For southern MB, the story will be rain today which should continue most of the day. Rainfall amounts should be about 15-25 mm over SE Manitoba including Winnipeg, with 25-35 mm possible over parts of SW Manitoba.

Thursday, October 09, 2008

Thanksgiving weekend outlook

Cool and unsettled conditions will be the main story for the upcoming Thanksgiving weekend over southern MB. A sharp frontal boundary is forecast to develop across the Dakotas on Saturday before a storm system tracks across southern MB on Sunday, followed by windy and cooler conditions on Thanksgiving Monday. The details..

Saturday should be cloudy and cool across southern MB as the frontal boundary begins to set up across the eastern Dakotas into northern Minnesota. This boundary will be separating warmer and drier conditions to the east from cool and wet conditions to the west. An area of rain will develop along this frontal boundary over the Northern Plains and spread into southern MB Saturday afternoon and evening. Rain may become heavy at times Saturday night into Sunday morning, with thunderstorms possible, as a low pressure system develops over the western Dakotas and tries to spread warmer air into southern MB. Rain from this system will continue to spread to the north and west of Winnipeg on Sunday, so there may be a break from precipitation Sunday afternoon over the Red River valley and SE Manitoba. Sunday night, a cold front from the low will sweep across Southern MB, bringing windy and cooler conditions on Monday, with clouds and a chance of showers.

My holiday weekend forecast for Winnipeg. Note that the timing of the precipitation will be subject to change based on how these systems develop over the next day or two. At this time, this is what the models are saying.. (updated Saturday morning)

Saturday..Cloudy and cool. Chance of showers this afternoon. High 9.
Saturday night..Periods of rain developing. Low 7.
Sunday..Rain heavy at times tapering off in the afternoon. Chance of a thunderstorm. Total rainfall amounts 15-25 mm. High 14.
Sunday night..Chance of showers. Low 5.
Monday..Mostly cloudy, breezy, cooler. Chance of a shower. High 8.

Saturday, October 04, 2008

Nice weekend.. showers moving in Monday

A beautiful weekend out there as the remnants of the massive upper ridge that gave record breaking warm temperatures over Alberta and western SK moves over Manitoba. We won't get quite as warm as the 25-29C readings enjoyed to our west this past week, however we will get into the mid to upper teens with plenty of sunshine both today and Sunday along with brisk south to southeast winds. Look for clouds to move in by Monday with rain developing as a frontal trough moves in from the west. Right now, rain amounts look to be in the 5-15 mm range for Winnipeg and the Red River valley, but local amounts of up to 25 mm are being hinted at by some models.

Wednesday, October 01, 2008

September a little warmer, a little wetter

September 2008 finished a little warmer and wetter than average, coming off a warmer and wetter than normal August. The mean monthly temperature at Winnipeg airport was 13.0C, or 0.7C above the 30 year average of 12.3C for September. (Sept 2008 averaged 13.3C at my site, 14.2C at the Forks) Temperatures averaged cooler than normal for the first week, then were generally near or above normal for the rest of the month. The highest temperature was a 29.2C reading on the 18th (29.6C at my site) while the lowest was -0.5C on the 27th, marking the official end of the growing season at the airport site. Elsewhere across the city however, September remained frost free with a monthly low of +1.4C at my site, and +3.4C at the Forks downtown. As a result, most flowers and gardens were still in bloom by month's end.

Rainfall for the month was above average at 77 mm (82 mm at my site - average September rainfall 52 mm) but that was mainly due to two main rain events on the 1st, and the 22-24th when thunderstorms brought locally severe thunderstorms and heavy rain. The rest of the month was fairly tranquil with minimal precipitation and frequent dry days, making for pleasant late summer weather… a welcome extension to a summer that started off cool and wet.

All in all, a pleasant end to the summer of 2008.