Thursday, February 04, 2016

Clipper system to bring snow across southern Manitoba this weekend

Map valid 6 pm Saturday evening shows band of snow and ice
over SW Manitoba pushing east as clipper system from SK
tracks across southern MB this weekend
A clipper system is forecast to track across southern Manitoba this weekend bringing an area of snow with it Saturday afternoon into Sunday. At this point, it looks like an inital band of snow will push across the regions Saturday afternoon, with possibly 2-4 cm of snow for Winnipeg and the RRV along with a risk of ice pellets over SW MB.  This band of snow will push off Saturday evening before another area of snow with the main clipper spreads across the area Saturday night into Sunday. At this point, models are suggesting the bulk of snow will fall mainly across western MB from Dauphin to Pilot Mound into North Dakota (10-15 cm possible) with lesser amounts of 5-10 cm for Winnipeg and 5 cm or less over SE Manitoba.  In addition, gusty NW winds are expected behind the system Sunday, so blowing and drifting snow will likely result in reduced visibilities in rural areas, especially west of Winnipeg to the SK border and south to the ND border.  Colder weather will follow in the wake of this system for the start of the new work week with highs in the minus teens and lows in the minus 20s for the first half of the week. 
 
Snowfall amounts (inches) forecast by NAM model valid
late Sunday. Bulk of snow expected north and west of Winnipeg
UPDATE: (Friday evening) NWS has issued blizzard watches for eastern ND and high wind watches for western ND for Sunday. Strong NW winds gusting to 80-90 km/h are expected on the backside of this system over much of North Dakota Sunday. The strong winds combined with falling or fresh snow will lead to poor visibilities in blowing snow especially over eastern ND and the RRV.  Although the strongest winds are expected in ND with this system, winds will be gusty over southwest MB and the southern RRV as well, so be prepared for  poor travelling conditions Sunday into Sunday night, especially south and west of Winnipeg.  

UPDATE: (Saturday afternoon):  A blowing snow advisory has been issued for Winnipeg and the Red River valley for Sunday as strong NW winds of 50-60 gusting to 70-80 km/h develop overnight into Sunday morning. The strong winds will combine with fresh or falling snow to produce poor visibilities in open areas, with blizzard-like conditions possible in some areas, especially in the southern RRV.  The extent of blowing snow will depend on how much new snow falls overnight and Sunday, which currently looks to be in the 5 cm range for most of the RRV, including Winnipeg.  Conditions should improve Sunday evening as winds decrease.  Note that NWS has issued blizzard warnings for eastern ND for Sunday, inlcluding the RRV from Pembina to the South Dakota border.

Friday, January 29, 2016

Mild end to January.. February to start on a cold note..

Other than a midmonth cold snap, temperatures
have been mainly above normal in January
January is ending on a mild note as another flow of mild Pacific air floods across the Prairies into southern Manitoba. Balmy west winds pushed temperatures up to +3.2C in Winnipeg today, some 14C above normal for late January and just 1.2C off the record high for the date (4.4C in 1992)   Above normal temperatures will continue over the weekend, although they will be cooling off from Friday's values with highs near freezing Saturday and -5 Sunday. The mild end to the month will ensure that January ends up above normal with an average temperature of around -14.5C, or 2C above the normal January mean of -16.4C.  This will be the fifth consecutive month with above normal temperatures in Winnipeg and southern Manitoba, stretching back to last September.



Turning colder for first half of February

Upper pattern for 2nd week of February
suggests below normal temps for MB/Ont
The outlook for February looks colder, at least for the first half of the month as the upper weather pattern changes to allow more prolonged periods of Arctic air into Manitoba. Long range models are indicating that the Arctic vortex over Baffin Island will dig an upper trof across Hudson Bay into eastern North America, while an upper ridge builds over the West Coast. This type of setup usually means a more sustained period of below normal temperatures for southern Manitoba. This will likely mean a colder than normal first half of February.. before hopefully a pattern change to milder weather for the latter half of the month.

850 mb temperature anomalies for 1st and 2nd weeks of February
shows sustained cold pattern coming up (ECMWF EPS guidance)  

 

A colder than normal February would be at odds with what history suggests February will be like during strong El Nino years (as we have this year)   A composite temperature plot of the past 6 strongest El Ninos since 1950 (image left) shows a tendency of above normal temperatures over the Northern Plains (and southern Prairies)  During the last very strong El Nino in 1997-98, February ended up as the warmest February on record in Winnipeg with a mean monthly temperature of -4.6C, some 9C above normal. The 2nd warmest February in Winnipeg, in 1878, was also during another very strong El Nino year. But there have been some exceptions.The Februarys of 1958 and 1966 were colder than normal in southern Manitoba, especially 1966 which featured a brutal cold snap in mid February that saw temperatures plummet to -45.0C in Winnipeg on the 18th, the second coldest temperature ever recorded here since 1872. But take heart, even in those cold Februarys, temperatures turned milder in the latter part of the month, including a record high of +11.7C in Feb 1958 on the 25th, Winnipeg' all time warmest February temperature. So if we do get that cold weather that is currently being suggested over the next two weeks, there's a good possibility that it won't last the entire month.

Tuesday, January 26, 2016

Snowy Wednesday morning commute.. then a mild slushy afternoon..

Weather map valid 6 am Wed morning shows area
of snow over RRV (blue) with freezing rain (red)
over southwest Manitoba (RGEM model)
A quick moving storm system over northern Alberta will be dropping southeast into southern Manitoba overnight, bringing a wintery mix of precipitation to the area. Snow will be spreading into the Parklands and northern Interlake regions after midnight reaching Winnipeg and the Red River valley by 5 am Wednesday morning. Snow will likely be heavy at times through the morning rush hour in Winnipeg with 5 to 10 cm possible between 6 am and noon. That will have a significant impact on the morning commute due to snow covered roads and poor visibility so plan on taking extra time getting to work or school Wednesday morning.  Further west, snow will likely mix with or change to freezing rain over southwest Manitoba where freezing rain warnings are in effect.

Meteogram for Winnipeg from ECMWF model shows
heavy burst of snow through Wed am rush hour
For Winnipeg, snow will taper off by noon before things will get a lot slushier in the afternoon as our winds shift into the west tapping milder air from Saskatchewan. This will send temperatures above freezing in the Red River valley including Winnipeg with afternoon highs near +2C expected. That will mean a lot of slush and melting snow on the roads into the evening rush hour, so make sure you have plenty of washer fluid if you're out driving Wednesday.    

Tuesday, January 12, 2016

Staying cold into next week.. then a warming trend

Southern MB will be locked into a cold weather pattern for the next little while until a moderating trend begins next week.  Temperatures this week will continue below normal (normal highs -13C, lows -23C) with a reinforcing shot of Arctic air this weekend when temperatures will struggle in the mid minus 20s, and lows in the minus 30s. This will be the longest stretch of below normal temperatures in southern MB since at least August. Long range guidance is hinting of a moderating trend by the middle of next week, with temperatures hopefully rising into the minus single digits by the end of the week.

Sunday, January 03, 2016

Mild start to January.. but colder weather on the way by next weekend

2016 is off to a mild start over southern Manitoba with temperatures above normal along with mainly sunny conditions. (Normal highs right now are -13C with lows of -23C) The mild and tranquil weather pattern is expected to continue much of this week, before a change to significantly colder weather (as in plug-in-your-car cold) moves in later in the week through next weekend.

Winnipeg forecast shows change to much colder weather by next weekend
850 mb temperature plot valid next Monday Jan 11th
from ECMWF shows large Arctic outbreak over Prairies

Temperatures this week will be mainly in the minus single digits with no significant precipitation expected through Thursday. On Friday, a storm system passing through the Dakotas will spread an area of snow across southern Manitoba, with a general 2-5 cm possible. Winds will shift into the north behind this system, heralding the arrival of much colder air for the weekend into early next week. Look for daytime temperatures in the minus 20s and nighttime lows in the minus 30s as the coldest airmass of the season pushes into the Prairies.



So once that cold air gets here, how long will it last?  The coldest core of the airmass looks like it will be coming through Sunday through Tuesday before a slight moderation next week. After that, it's tough to say how January will end up, however given past previous strong El Nino episodes, the odds favour a milder than normal January over southern MB.  Of the past 6 strong El Ninos since 1950, five Januarys were milder than normal here, including during the record strong El Ninos of 1997-98 and 1982-83.  (see composite map below)  Note that cooler than normal weather is more likely over the southern US due to a strong southern jet stream bringing more frequent storm systems and precipitation from California through Texas to the US southeast.  

JANUARY TEMPERATURE ANOMALIES DURING STRONG EL NINOS
Composite map showing average temperature anomalies in January
based on average of past 6 strong El Ninos since 1950