Wednesday, April 2, 2014

WNTV Blog: Multi-Day Severe Threat and Heavy Midwest Snow

Chile Earthquake
The recent Chile earthquake on Tuesday evening was just another quake in the string of quakes to effect the Eastern Pacific region from North America to South America. This one, however, was MUCH greater than those in near Los Angeles, CA and Yellowstone National Park. I'm hoping this isn't turning out to be a trend...



Tsunami Threat Immediately After Quake
This raised concerns of a Tsunami just after the quake. Note the forecast wave propagation map below hours after the quake off the Chilean Coast.



Interestingly, a Tsunami Advisory had been issued for the Hawaiian Islands through the morning hours of Wednesday in fear that the potential wave could have been hazardous to swimmers or boaters!



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Multi-Day Severe Threat
As we continue through the early part of April, strong to severe thunderstorm will be possible. This multi-day severe weather threat appears to continue through the end of the week; see more on that below. Here's a picture of hail that fell in Fulton, MO on Wednesday morning.



More hail in Columbia, MO from AM Wednesday



Thanks to @BCBaseballLeag for the picture below from Columbia, MO. Glad you didn't see baseball size hail there! The good news is that weather conditions will be improving by PM Friday/Saturday, so you might be able to use that grill you've covered up!



Lackluster Severe Season Thus Far
It certainly has been a quite severe weather season thus far. As of the April, 1st the PRELIMINARY tornado count across the nation was only 70. The 2005-2012 average is around 250! Interestingly, Oklahoma City, OK averages around 42 SLIGHT RISK days and 7 MODERATE RISK days per year.



Days Since Last Tornado Warning
The graphic below from IEM, shows the number of days since the last tornado warning has been issued by any specific National Weather Service Office. Interestingly, there are several NWS offices in the central part of the country that (as of midday Wednesday) that have gone nearly 300 days or more without having a tornado warning issued in their country warning area! That certainly is a long since these are areas typically more prone to tornadic activity.



Tornado Warnings Issued January through March
This is another interesting look at how quiet this severe weather season has been. The graph below shows how many tornado warning have been issued during the January - March time frame across the nation. Note that 2014 has been nearly one of the quietest years since 1986. 2012 was a fairly active start to the year, while in 2008, there were more than 1,000 tornado warnings issue January - March!



2014 Tornado Reports
According to the Storm Prediction Center, as of April 1st, there have only been 70 PRELIMINARY tornado reports. Last year at this time, there were 153 by now; the (2005-2013) average is 244 PRELIMINARY tornado reports through April 1st.



Stormy Weather Ahead
Here's the weather outlook through PM Friday. Note the large low pressure system wrapping up over the central part of the country through then. This storm will be very dynamic with heavy rain, severe storms and shovelable snow chances.



MODERATE RISK THURSDAY
The Storm Prediction Center has issued a MODERATE RISK of severe weather for Thursday as another impluse of energy from the Pacific moves into the central part of the country. This more vigorous wave of energy will help to promote more widespread severe weather for Thursday, which would likely be in the form of large hail, damaging winds and tornadoes!
Here's the latest thinking from the Storm Prediction Center:

...ERN SRN PLAINS THROUGH LOWER-MID MS VALLEY AND WRN TN VALLEY... LATEST MODEL GUIDANCE SUGGESTS EWD PROGRESSION OF UPPER TROUGH MAY BE A TAD SLOWER THAN PREVIOUS RUNS...BUT OVERALL TRENDS REMAIN FAIRLY CONSISTENT. A LARGE WARM SECTOR CHARACTERIZED BY MID 60S DEWPOINTS WILL BE IN PLACE AT THE BEGINNING OF THE PERIOD. SOME EARLY ELEVATED CONVECTION ASSOCIATED WITH STRONG WARM ADVECTION AND A WEAK UPPER IMPULSE IS POSSIBLE ACROSS PARTS OF THE LOWER AND MID MS VALLEY...BUT SHOULD QUICKLY MOVE N AND E AND IS NOT EXPECTED TO BE A CONCERN FOR LATER AIRMASS DESTABILIZATION. BY AFTERNOON...STEEP MID LEVEL LAPSE RATES GREATER THAN 7 DEG C/KM ATOP SFC TEMPERATURES IN THE 70S TO NEAR 80 F AND MID 60S DEWPOINTS WILL RESULT IN MODERATE TO STRONG INSTABILITY WITH MLCAPE VALUES PROGGED NEAR 1500-2500 J/KG. AS THE CAP ERODES WITH SFC HEATING...IT IS POSSIBLE A STORM OR TWO MAY DEVELOP IN THE WARM SECTOR ACROSS SE MO/ERN AR AS LOW LEVEL JET INCREASES BY LATE AFTERNOON. LARGE HAIL AND STRONG WINDS WOULD BE THE MAIN THREAT WITH THESE STORMS INITIALLY. HOWEVER...THE MAIN THREAT APPEARS TO BE FURTHER WEST FROM SW/S-CNTRL MO INTO NW/N-CNTRL AR JUST AHEAD OF EWD ADVANCING COLD FRONT. DEEP LAYER SHEAR AND LOW LEVEL HODOGRAPHS WILL BE FAVORABLE FOR DISCRETE SUPERCELLS CAPABLE OF VERY LARGE HAIL...DAMAGING WIND GUSTS AND TORNADOES. AS THE FRONT QUICKLY SHIFTS EWD...LOW LEVEL SHEAR WILL INCREASE AS WILL THE TORNADO THREAT. QUESTIONS REMAIN AS TO HOW LONG STORMS WILL REMAIN DISCRETE AS THE COLD FRONT BEGINS TO MOVE MORE QUICKLY EWD AS THE UPPER TROUGH BEGINS TO EJECT EWD...BUT AT LEAST A SMALL WINDOW EXISTS AROUND 00Z FOR DISCRETE CELLS. THEREAFTER...UPWARD GROWTH INTO ONE OR MORE QLCSS ARE EXPECTED TO DEVELOP AND MOVE ACROSS SE MO/ERN AR TOWARD THE WRN OH/TN VALLEY INTO THE EVENING...ACCOMPANIED BY AN INCREASING THREAT FOR DAMAGING WINDS.



Severe Threat Friday
Here's the latest thinking from the Storm Prediction Center regarding Friday's storm potential:

...PORTION OF THE SERN STATES THROUGH TN AND OH VALLEYS... A PRE-FRONTAL SQUALL LINE SHOULD BE IN PROGRESS OVER THE OH...TN AND LOWER MS VALLEYS EARLY FRIDAY. SUFFICIENT PRE-CONVECTIVE INSTABILITY WILL EXIST IN THE PRESENCE OF STRONG DEEP LAYER WINDS FOR A THREAT OF DAMAGING WIND AS ACTIVITY DEVELOPS EWD DURING THE MORNING INTO THE EARLY AFTERNOON. HOWEVER...TENDENCY WILL BE FOR MOIST AXIS TO EVENTUALLY BE PINCHED OFF OVER THE OH VALLEY...WHILE THE STRONGER LOW-MID LEVEL WINDS AND DEEPER FORCING GRADUALLY LIFT NEWD AWAY FROM THE MORE UNSTABLE WARM SECTOR PRESENT OVER THE SERN STATES. THIS SUGGESTS GREATER SEVERE THREAT WILL BE FROM MORNING INTO MID AFTERNOON.



Heavy Precipitation Outlook
The several day rain/thunder event will have several inches of precipitation falling across the middle part of the country. Unfortunately, this could lead to some flooding in parts of the Ohio Valley.



Winter Weather Headlines
Here are the winter weather headlines that have been posted by the National Weather Service. Note that some within the winter storm warned area (in pink) could see as much as 6" to 12" or more through Friday.



Upper Midwest Snow Potential





Probability of at Least 4" Snow or More
The probability of at least 4" of snow or more through AM Saturday appears to be the greatest across east-central Minnesota through the U.P. of Michigan. In fact, it's almost 100% that northern Wisconsin and the U.P of Michigan will in fact see 4" or more. The Twin Cities has a 70% chance of seeing at least 4" of snow or more.



Probability of at Least 8" of Snow or More
The probability of at least 8" of snow or more drops a bit, but is still




Minneapolis Snow Stats
By the way, as of Wednesday, April 2nd, the Twin Cities had seen 63.0" of snow this season. In order to get to the 3rd snowiest season on record, we'd still have to get another +2ft. of snow! However, we only need another 12.5" to get to the 10th snowiest season on record. Here's a list of the top seasonal snows in the Twin Cities:




April Snow Stats
Here's another interesting stat for you... If current forecasts hold, we could certainly be close to one of our top 3 April snowfalls on record! Here's a list of the top 10 April snowfalls on record for the Twin Cities:

"Heavy snows in April are fairly common in Minnesota's past. The transition from winter to spring can spawn some rather strong storms and given the right conditions, can also tap into leftover cool air from the winter. Looking through historical anecdotes, the greatest chance of having a large snowstorm appears to be in the first half of the month. One of the greatest April snowstorms (besides the April 5-7, 2008 event) was the storm that began on April 5, 1933. The old Pigeon River Bridge crossing in Cook County saw 28 inches in one day from that storm. This still stands as the 24 hour state record for snowfall in April. Two Harbors in Lake County saw 17 inches of snow from the 1933 storm. The largest April snowstorm in recent memory is the April 17-19, 2013 event that brought 17.7 inches at Duluth and 7.3 inches in the Twin Cities."

See the full story on Historical April Snows from the UofM Climatology Department HERE:





Thanks for checking in and have a great rest of your week! Don't forget to follow me on Twitter @TNelsonWNTV