Still not a very good picture on snow accumulations. This still looks like mainly a snow/sleet storm with up to 1.5 inches of liquid equivalent possible.
Here are what the soundings for the airport are saying:
NAM has now beginning between 11:30 and midnight via bufkit... all snow through noon... mixing with sleet between 12PM and 2 PM... changing to sleet after 2 PM.. back to snow after 8:00 PM... Most of the precip falls before lunch time.
GFS has a relatively deep isothermal layer between 700 mb and 850 mb are so between 5:00 AM and 8:00 AM. Due to potentially high precip rates I still think this would be mostly snow. We could see some sleet mix kick in around 10:00 AM with a change to all sleet no later than noon... back to snow by around 6:00 PM
I'll just use a combo of these 2 to make my forecast:
Friday night: Snow... mainly after midnight
Saturday: Snow possibly mixed with sleet between 7:00AM and 11:00 AM. Snow/sleet mix between 11:00AM and 1:00 PM... Sleet between 1:00 PM and 7:00 PM...
Saturday night: Light snow decreasing to flurries later...
As of right now it looks like most of the precip will fall as snow at RDU... Some more sleet may mix in and the change over may be earlier to the south and the east.
The snow amount prediction is of very low confidence right now... Expect 6-12 inches over much of the triangle. Closer to 6 inches on the very southern and eastern regions. This would place Cary and North Raleigh at about 8-10 inches.
But again... the snow/sleet line will be influenced by mesoscale features which are very difficult to predict.
Friday, January 29, 2010
8:15 AM forecast Update
The storm should begin Friday night. Some of the early radar returns will probably not reach the ground. This precip will saturate the column and place our surface temperature below freezing, where it will potentially remain below freezing through early Monday morning.
Friday Night: Snow after 11 PM.. Possibly mixing with sleet.
Saturday: Snow mixing with and then changing to sleet after noon. Freezing rain mixed with sleet is possible between 2 and 4 pm. Changing back to snow Saturday evening.
Saturday night: A chance of light snow ending as flurries.
Total snow and sleet accumulations of 5-10 inches possible.
The triangle will be very very close to the snow/sleet transition line for most of the event.. making snowfall prediction totals very difficult. Will update again this afternoon.
Friday Night: Snow after 11 PM.. Possibly mixing with sleet.
Saturday: Snow mixing with and then changing to sleet after noon. Freezing rain mixed with sleet is possible between 2 and 4 pm. Changing back to snow Saturday evening.
Saturday night: A chance of light snow ending as flurries.
Total snow and sleet accumulations of 5-10 inches possible.
The triangle will be very very close to the snow/sleet transition line for most of the event.. making snowfall prediction totals very difficult. Will update again this afternoon.
Thursday, January 28, 2010
5:00 PM update
Hold the phone. The 18z American models just came in colder than the 12z models. This is due to a very slight shift south of the lower level features of the storm. This is why this forecast is very difficult in regards to precip type (sleet or snow at this point) and snow accumulations.
Models though have been very consistent in dropping about 1 - 1.5 inches of liquid precip. The surface temp looks plenty cold enough. I'm feeling very confident that the predominating precip type will either be sleet or snow. Really tough to guess on the snow amts.
Models though have been very consistent in dropping about 1 - 1.5 inches of liquid precip. The surface temp looks plenty cold enough. I'm feeling very confident that the predominating precip type will either be sleet or snow. Really tough to guess on the snow amts.
2:30 PM update
All of the models have trended the surface low north... therefore a bit more warm air is advecting over the cold dome. Although this could lead to an even stronger and deeper cold dome... Will need to add more sleet to the forecast and cut snow amounts in half. This is still subject to change. But again all precip would remain frozen.
Friday afternoon: A slight chance of light rain or snow. High 40
Friday night: Snow mixed with some sleet.. especially after 3:00 AM. Changing to all sleet by 7 AM. The snow and sleet could be heavy at times. low 27
Saturday: Sleet possibly mixed with snow.. changing to light snow after after 5:00 PM High 28
Total snow and sleet accumulations of 5-9 inches
Friday afternoon: A slight chance of light rain or snow. High 40
Friday night: Snow mixed with some sleet.. especially after 3:00 AM. Changing to all sleet by 7 AM. The snow and sleet could be heavy at times. low 27
Saturday: Sleet possibly mixed with snow.. changing to light snow after after 5:00 PM High 28
Total snow and sleet accumulations of 5-9 inches
Wednesday, January 27, 2010
Weekend winter storm update 11:00 PM
0z American models are in. The NAM and GFS are actually in pretty decent agreement right now, especially in regards to the triangle. Both models are showing about 1.25ish inches of liquid precip for the Triangle... most of which will fall as snow with possible snow pellets and sleet mixed in. The timing and precip intensity could still change. Still feel very confident that whatever falls will be frozen.. whether it be ice or snow. The 2 big questions from this storm are 1) will it be ice or snow? and 2) how much precip will we get. Subtle changes can lead to different results in regards to both of these question.
Now.. with the above caution in mind... taken literally these two models show snow amounts of around a foot for the triangle. Could be more or less depending on how much sleet is present.
Friday afternoon - 30% chance of afternoon snow - High near 40
Friday night - Snow... possibly mixed with sleet - Low near 27
Saturday - Snow tapering off to flurries in the evening. High near 29
Saturday night - Flurries before midnight and then clouds decreasing . Low near 19
Total accumulation of 9-15 inches possible.
Will update after the 12z data is in... sometime tomorrow afternoon/evening.
Now.. with the above caution in mind... taken literally these two models show snow amounts of around a foot for the triangle. Could be more or less depending on how much sleet is present.
Friday afternoon - 30% chance of afternoon snow - High near 40
Friday night - Snow... possibly mixed with sleet - Low near 27
Saturday - Snow tapering off to flurries in the evening. High near 29
Saturday night - Flurries before midnight and then clouds decreasing . Low near 19
Total accumulation of 9-15 inches possible.
Will update after the 12z data is in... sometime tomorrow afternoon/evening.
Friday night/ Saturday winter storm update
Basic forecast idea will remain unchanged. GFS and ECMWF keeps the low further south than the NAM and keep it virtually an all snow event with some sleet mixing in late Friday night/Early Saturday morning. NAM has much more precip but looks to be a bit over amplified. The key will be to track the 850 mb frontogenesis. Expect heavy snow bands to set up along and north of the 850ish mb low.
Will go with GFS/ECMWF blend as far as first call amounts...
Friday - 30% chance of light snow. Accumulation of less than an inch
Friday night - Snow mixed with sleet. 4-7 inches accumulation possible
Saturday - Snow mainly in the morning possibly mixed with sleet. 2-4 inch accumulations possible.
Will go with GFS/ECMWF blend as far as first call amounts...
Friday - 30% chance of light snow. Accumulation of less than an inch
Friday night - Snow mixed with sleet. 4-7 inches accumulation possible
Saturday - Snow mainly in the morning possibly mixed with sleet. 2-4 inch accumulations possible.
Tuesday, January 26, 2010
Friday Night/Saturday storm
Classic setup for a major southeastern winter storm looking more likely. A low pressure system associated with a moist southern jet will enter the continental US soon. This low pressure will move east into Texas and move into the Alabama/Mississippi coast. At the same time a fairly strong high pressure will strengthen as a polar vorticity move southeast toward the great lakes. The high pressure will spread its energy from the midwest through the great lakes. This will set up a classical cold air damming scenario with a strengthening high to the north. The low pressure will then move east/northeast off the coast of North Carolina bringing the potential of significant overrunning precipitation.
Quick model rundown: The NAM is the furthest north with a more liquid scenario. This model is an outlier. The long term of the NAM is known to have issues, therefore will through this model out for now.
The ECMWF is much further south and suggest an all snow event for the triangle. This model is extreme, yet is supported by most other models in regards to the more southern path
The GFS is in between the ECMWF and the NAM but leans much closer to the ECMWF. GFS bufkit shows a snow/sleet scenario for the triangle. Will lean toward a balance between these 2 models. Also.... will lean more toward snow as this is a pretty classic setup for an RDU snowfall... but most winter events in North Carolina contain a mix of precip. This will be borderline in regards to temps near the 850 level.. however surface temps will likely stay below freezing throughout the event..
With that in mind... Things can certainly change.
Friday afternoon: A chance of light snow
Friday night: Snow and sleet likely
Saturday: Snow likely
No amounts yet... too early
Quick model rundown: The NAM is the furthest north with a more liquid scenario. This model is an outlier. The long term of the NAM is known to have issues, therefore will through this model out for now.
The ECMWF is much further south and suggest an all snow event for the triangle. This model is extreme, yet is supported by most other models in regards to the more southern path
The GFS is in between the ECMWF and the NAM but leans much closer to the ECMWF. GFS bufkit shows a snow/sleet scenario for the triangle. Will lean toward a balance between these 2 models. Also.... will lean more toward snow as this is a pretty classic setup for an RDU snowfall... but most winter events in North Carolina contain a mix of precip. This will be borderline in regards to temps near the 850 level.. however surface temps will likely stay below freezing throughout the event..
With that in mind... Things can certainly change.
Friday afternoon: A chance of light snow
Friday night: Snow and sleet likely
Saturday: Snow likely
No amounts yet... too early
1/26/2010 Friday Night/Saturday Storm
**Potential Major Winter Storm this Weekend for Central North Carolina**
A quasi perfect set up for a classic winter storm could be in the works for this weekend. Models are not in complete agreement right now and timing/exact location of the arctic high and the surface low need to be worked out.
But models have been consistent in showing the potential for major winter storm for portions of the south east including North Carolina. Up to a foot of snow could fall in parts of central North Carolina. Severe ice accumulation could also occur near the triangle depending on the location of the low and how much cold air advects into the region.
Will give a much more detailed outlook after the 12z models are in.
A lot of uncertainty remains with this system... as it is still several days away from effecting the southeast.
A quasi perfect set up for a classic winter storm could be in the works for this weekend. Models are not in complete agreement right now and timing/exact location of the arctic high and the surface low need to be worked out.
But models have been consistent in showing the potential for major winter storm for portions of the south east including North Carolina. Up to a foot of snow could fall in parts of central North Carolina. Severe ice accumulation could also occur near the triangle depending on the location of the low and how much cold air advects into the region.
Will give a much more detailed outlook after the 12z models are in.
A lot of uncertainty remains with this system... as it is still several days away from effecting the southeast.
Thursday, January 7, 2010
1/8 light snow event.
Light snow will fall between midnight and daybreak.
Low level dry air and lack of a good lifting mechanism mean precip will be at a premium.
I'm expecting anywhere from a light dusting to 1/2 inch for most of the triangle. Some locations could see a maximum of one inch. Models are in very good agreement right now in keeping precip totals at less than .05 inches of liquid equivalent. This translates to just over half an inch max however, the precip should stay scattered and the models generalize scattered precip over a broad area. So not everyone will see .05 inches.
I do think most folks will wake up to a dusting to half an inch on the ground tomorrow.
Low level dry air and lack of a good lifting mechanism mean precip will be at a premium.
I'm expecting anywhere from a light dusting to 1/2 inch for most of the triangle. Some locations could see a maximum of one inch. Models are in very good agreement right now in keeping precip totals at less than .05 inches of liquid equivalent. This translates to just over half an inch max however, the precip should stay scattered and the models generalize scattered precip over a broad area. So not everyone will see .05 inches.
I do think most folks will wake up to a dusting to half an inch on the ground tomorrow.
Subscribe to:
Posts (Atom)