This looks to be our *last* winter storm of the season, as northern stream blocking and the Pacific longwave patterns WILL be shifting after this storm. Warmer weather looks to be well on its way by early-mid April.
Here are some of the main points, with more details below them:
1.) Track of the low is becoming more confident. The low looks to track through the Ohio Valley in an ideal position to bring the area heavy snow, ice, and gusty winds.
- Current ensemble consensus is shown in this map:
There are several arguments in favor of going against the ECMWF (which is shown below):
- Blocking is too strong on the model. This is a result of its amplification bias, which tends to split the jet stream apart too "much" and for too long of a time because it amplifies the Polar blocking pattern more so than it needs too.
- The ECMWF has been showing a southern bias all winter (which is unusual), and therefore, its likely that its both too weak, and too far south.
2.) Moisture will be quite sufficient with this system. The system itself will tap into the Subtropical Jet, which will provide it with more than enough moisture to produce heavy precipitation.
- The GFS has circumvented the deepest moisture further to the southeast due to the development of the secondary low off of the coast of the Carolinas. The development of the secondary low will determine the extent of the precipitation due to the fact that if the secondary low forms much quicker than expected, the flow of moisture will be cut-off into the Ohio Valley. This will depend heavily on the strength of the blocking, and strength of the low pressure system itself, which is discussed below.
3.) Cold air will definitely be in place. Based on the latest forecasted thermal profiles, they look to be nearly IDEAL for snow late Saturday night through Sunday. 850 millibar temperatures will be in the -3 to -8 degree range across the area during the snowstorm, which is more than sufficient for excellent ice crystal production ("efficient" snowfall).
- The 06z and 12z GFS forecasts clearly show the ideal thermal profiles for snow AREAWIDE. Although it is possible that sleet, freezing rain, and even plain rain mix in (especially in the initial stages of the storm), the majority of the time, precipitation will be in the form of snow. Surface temperatures during the times of heaviest snow on both GFS runs were below 30, while 850 millibar temperatures were in the range of -4 to -6. Low level thermal properties is also trending colder on the models, so I don't see precipitation type being a major issue with this winter storm.
4.) Strength of this system is still in question, because it will depend on the strength of the downstream blocking pattern, the strength of the lead shortwave, and how quickly a secondary low pressure system develops to our east, just off of the coast of North Carolina. Other than that, this system looks to fairly strong, and probably strong enough to produce strong, gusty winds.
-It's likely that the system maintains a strength in between 993 and 997 millibars, before the primary takes over. This is all depending on the strength of the lead shortwave, which could be underestimated, especially in a pattern like this. I won't make a call like that though, as its only based on speculation. This will be resolved in coming days.
That's about all of the details I will provide now.
Also, I will be leaving this Friday afternoon for the wonderful state of Florida. NO updates will be released after that until I have a chance to access the internet on Tuesday. For updates on this potential winter storm, refer to your local broadcast meteorologist, and/or visit the NWS's website at www.crh.noaa.gov/iwx for further details.
Don't forget to like NWS Northern Indiana on Facebook as well for the latest updates.
Remember.. This event is FAR from set in stone, and some details, especially with regards to initial precipitation types and amounts are still in question, but its ENTIRELY possible that we see at least moderate snow amounts (3-6 inches of snow), and moderate icing amounts (0.05 to 0.25 inches of ice.).
Here are some of the main points, with more details below them:
1.) Track of the low is becoming more confident. The low looks to track through the Ohio Valley in an ideal position to bring the area heavy snow, ice, and gusty winds.
- Current ensemble consensus is shown in this map:
There are several arguments in favor of going against the ECMWF (which is shown below):
- Blocking is too strong on the model. This is a result of its amplification bias, which tends to split the jet stream apart too "much" and for too long of a time because it amplifies the Polar blocking pattern more so than it needs too.
- The ECMWF has been showing a southern bias all winter (which is unusual), and therefore, its likely that its both too weak, and too far south.
GFS (below the ECMWF chart) vs. ECMWF
 |
| 12z ECMWF has the primary low down near the Gulf Coast. |
 |
| 12z GFS has a more reasonable solution with the primary low in Kentucky, before transferring to the secondary farther east. |
 |
| This is the 06z GFS, which is a bit further north than the 12z GFS is. These discrepancies are being resolved though, and we now have general model agreement (disregarding the ECMWF). |
2.) Moisture will be quite sufficient with this system. The system itself will tap into the Subtropical Jet, which will provide it with more than enough moisture to produce heavy precipitation.
- The GFS has circumvented the deepest moisture further to the southeast due to the development of the secondary low off of the coast of the Carolinas. The development of the secondary low will determine the extent of the precipitation due to the fact that if the secondary low forms much quicker than expected, the flow of moisture will be cut-off into the Ohio Valley. This will depend heavily on the strength of the blocking, and strength of the low pressure system itself, which is discussed below.
 |
| 06z GFS 6 hour precipitation forecast at hour 102 |
 |
| 12z GFS trended slower with the system, but with heavier precipitation in the Ohio Valley/Lower Great Lakes. This needs to be watched. |
- The GGEM is also quite moist with this system, bringing heavy snow banding, but mainly for areas along and east of North-Central Indiana (Fort Wayne, Toledo, Southeast Michigan, NW Ohio, etc.).
- The 06z and 12z GFS forecasts clearly show the ideal thermal profiles for snow AREAWIDE. Although it is possible that sleet, freezing rain, and even plain rain mix in (especially in the initial stages of the storm), the majority of the time, precipitation will be in the form of snow. Surface temperatures during the times of heaviest snow on both GFS runs were below 30, while 850 millibar temperatures were in the range of -4 to -6. Low level thermal properties is also trending colder on the models, so I don't see precipitation type being a major issue with this winter storm.
4.) Strength of this system is still in question, because it will depend on the strength of the downstream blocking pattern, the strength of the lead shortwave, and how quickly a secondary low pressure system develops to our east, just off of the coast of North Carolina. Other than that, this system looks to fairly strong, and probably strong enough to produce strong, gusty winds.
-It's likely that the system maintains a strength in between 993 and 997 millibars, before the primary takes over. This is all depending on the strength of the lead shortwave, which could be underestimated, especially in a pattern like this. I won't make a call like that though, as its only based on speculation. This will be resolved in coming days.
That's about all of the details I will provide now.
Also, I will be leaving this Friday afternoon for the wonderful state of Florida. NO updates will be released after that until I have a chance to access the internet on Tuesday. For updates on this potential winter storm, refer to your local broadcast meteorologist, and/or visit the NWS's website at www.crh.noaa.gov/iwx for further details.
Don't forget to like NWS Northern Indiana on Facebook as well for the latest updates.
Remember.. This event is FAR from set in stone, and some details, especially with regards to initial precipitation types and amounts are still in question, but its ENTIRELY possible that we see at least moderate snow amounts (3-6 inches of snow), and moderate icing amounts (0.05 to 0.25 inches of ice.).
Did you order this just because you're going to Florida?!? -Mom :)
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