Severe weather concerns early this week followed by a cooling trend with a hard freeze potential late week

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A very nice weekend wrapping up with some scattered high clouds and temperatures in the 60s and 70s, warmest out west. This week we’ll be dealing with the year’s first chance at thunderstorms. Severe weather is at least a possibility with the greatest risk in Mid Missouri east of Kansas City and west of STL.  As is always the case, timing will be an issue to contend with, a faster cold front on Tuesday pushes that chance toward STL while a slower evolution would bring that chance westward to KC.

Overall, we’ll begin to return to a cooler pattern as the upper level winds return to the western ridge/eastern trough pattern they have “defaulted” to so often during February.  This will bring about a return to dry weather as well, so if your area misses the early week rain chances, that could conceivably be it for the month.  It will be nearing April by this time next week, so the cold simply doesn’t have the power it once did 4-6 weeks ago, and it will begin to moderate by early NEXT week.

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Take a look at this meteogram (for KC) showing the dip with a few nights below freezing late this week.  The trend has been colder over the past few days and it’s possible it may be downright chilly but bright next Fri/Sat. We’re still several weeks away from the average date of the last frost and freeze so it’s still too early to be planting sensitive plants. If you’ve rushed the season a bit, here’s your alert to be ready to cover things up late this week.

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This map shows the average last date of a hard freeze.  A hard freeze is a temperature of 28F or lower for three or more hours.  It used to be known as a “killing freeze”.  All of the area is still well within the window of a killing freeze.  Parts of S IL begin to move beyond it by the middle of next week, but the rest remain vulnerable well into early April.  The urban core areas of KC/STL usually are a little ahead of the more rural areas, thanks to the heat island effect.

LAST HARD FREEZE

Severe weather chances are greatest from SW-central MO and really in between the east and western districts.  That’s where the line of storms is expected to erupt according to the higher resolution computer model guidance and the biggest risk is large hail.  Storms would weaken as they headed eastward toward the eastern district. There is at least a marginal risk over most of the area.

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Rainfall becomes harder to predict as we move into the thunderstorm season, as it all depends upon where the storms develop and track.  Often times just a few miles can separate areas missed completely from areas getting downpours.  This can be seen on these model charts, but all seem to agree the highest totals will be north of the region along the MO/IA state line with quarter to 1/2″ amounts elsewhere.

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The week in review:

Last week the main story was some very warm weather over the Plains late last weekend which expanded into the Midwest Monday ahead of a cold front.  Highs warmed well into the 80s and even some 90s over Kansas and Nebraska.   The first map shows Sunday afternoon temperatures:

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Monday readings were near or above 90 over western and central KS and NE. Kansas City set a record high of 83 breaking the old record of 82, set just three years ago in the very warm Spring of 2012.

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The front which helped bring in the warmth cooled things down midweek while an upper level system brought the first measurable rains to much of the western district this month.  Prior to this event, KC had no measurable rain for March.

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The west remains extremely dry relative to average for March to date with only 25-50% of the average March rain.  The east is also dry with 50-90% of the average March rains, while extreme SEMO/SW IL is much wetter than average.

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The very warm last 7 days have helped bring March into warmer than average levels in the west, while the eastern district remains slightly below average.  For the U.S. in general, the month so far has been warm west and north and cool south central and northeast.

 

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Southern Hemisphere Tropics:

Peak season in the southern hemisphere tropical cyclone season continues, although there were fewer storms than the four mentioned last week.

Tropical Cyclone Nathan (18P) which has been looping around off the Queensland Coast since early in the month finally made landfall on the Cape York Peninsula.  The system finally organized into a small, but strong tropical cyclone. The system then regenerated in the Gulf of Carpentaria, then made a second landfall over Arnhem Land near Gove.  From there, the system moved back over water just off the north coast of the Northern Territory.

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Nathan may remain just far enough offshore to remain around most of this week.

Tropical Cyclone Reuben (20P) developed southeast of Fiji and northeast of NZ’s north island late week.  The system was far from land and at the edge of the warmer waters and was already showing signs of morphing into a mid latitude gale low as of Sunday afternoon.

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We’ll have another update out next weekend as we look into the opening days of April.

 

 

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