Ice Storm!
As I mentioned a couple of days ago, the NWS FTW picked up on it first this morning and now the models are locked in on it...the upper level system is indeed digging more than expected. The result is an even more intense upper level low developing and moving across the area on Thursday..slower than earlier model forecasts.
At the same time, the arctic front is apparently intent on coming in faster than forecast....pretty typical for strong, shallow arctic airmasses. The models never handle these events well at all and forecasters get suckered every time. :-) Here at 16z, it is already past Tulsa and OKC and knocking on the door of Wichita Falls. Precip is already erupting just behind the front in OK.
As far as the severe thunderstorm threat, it is very high today through Thursday...even behind the front. The main threat will be hail. The best chance for surface based supercells has shifted further WSW as a result of the upper low/trough coming in slower. The triple point and dryline appear to stay well SW of the DFW area down around Brownwood to Brady to Junction vicinity where I would be if I were chasing today. I think the tornado threat will be a bit better down there. Up in N TX and S/SE OK, storms will erupt along the front as a squall line....and a pretty good one at that. :-) I just don't see support for discreet supercells forming out ahead of it today....the upper energy and dynamics are lagging too far to the west.
Back to the impending ice storm. Current indications are that impressive upper air dynamics will focus on N TX and S OK (The Red River Valley) for strong elevated convection behind the front. With dewpoints forecast to drop into the mid 20's, wet bulbing (evaporative cooling) should slam us to or below freezing by sometime Thursday morning. The strongest dynamics aloft move across later in the 18-00z time frame resulting in intense elevated convection and yes....sleet or snow with lightning and thunder! :-) This should produce copious amounts of freezing rain and sleet and even small hail across the area with a better chance of snow later in the event and in particular across the Red River valley into S OK. Fortunately, ground temperatures are balmy, so only bridges/overpasses, trees, and power lines are going to freeze.
The hedache in these types of events is just how much freezing rain will occur. It's always a delicate balancing act which is impossible this far in advance to determine with any sort of accuracy. Freezing rain events mostly occur in a narrow geographic area as well making it even more of a headache to forecast. It's a crap shoot at this point. If things evolve to support freezing rain, then this could certainly end up being a significant storm with heavy glazing of ice. If the air column is abit colder, then it would all be sleet..and still a pretty darned significant event...but relatively harmless.
Keep an eye on this one folks. it is going to be a wild event and certainly one that makes this weather weenie all giddy. :-Þ If the upper air system digs and intensifies even more, then the event becomes even more significant.
More later as conditions warrant. ;-)
At the same time, the arctic front is apparently intent on coming in faster than forecast....pretty typical for strong, shallow arctic airmasses. The models never handle these events well at all and forecasters get suckered every time. :-) Here at 16z, it is already past Tulsa and OKC and knocking on the door of Wichita Falls. Precip is already erupting just behind the front in OK.
As far as the severe thunderstorm threat, it is very high today through Thursday...even behind the front. The main threat will be hail. The best chance for surface based supercells has shifted further WSW as a result of the upper low/trough coming in slower. The triple point and dryline appear to stay well SW of the DFW area down around Brownwood to Brady to Junction vicinity where I would be if I were chasing today. I think the tornado threat will be a bit better down there. Up in N TX and S/SE OK, storms will erupt along the front as a squall line....and a pretty good one at that. :-) I just don't see support for discreet supercells forming out ahead of it today....the upper energy and dynamics are lagging too far to the west.
Back to the impending ice storm. Current indications are that impressive upper air dynamics will focus on N TX and S OK (The Red River Valley) for strong elevated convection behind the front. With dewpoints forecast to drop into the mid 20's, wet bulbing (evaporative cooling) should slam us to or below freezing by sometime Thursday morning. The strongest dynamics aloft move across later in the 18-00z time frame resulting in intense elevated convection and yes....sleet or snow with lightning and thunder! :-) This should produce copious amounts of freezing rain and sleet and even small hail across the area with a better chance of snow later in the event and in particular across the Red River valley into S OK. Fortunately, ground temperatures are balmy, so only bridges/overpasses, trees, and power lines are going to freeze.
The hedache in these types of events is just how much freezing rain will occur. It's always a delicate balancing act which is impossible this far in advance to determine with any sort of accuracy. Freezing rain events mostly occur in a narrow geographic area as well making it even more of a headache to forecast. It's a crap shoot at this point. If things evolve to support freezing rain, then this could certainly end up being a significant storm with heavy glazing of ice. If the air column is abit colder, then it would all be sleet..and still a pretty darned significant event...but relatively harmless.
Keep an eye on this one folks. it is going to be a wild event and certainly one that makes this weather weenie all giddy. :-Þ If the upper air system digs and intensifies even more, then the event becomes even more significant.
More later as conditions warrant. ;-)
posted by Steve Miller TX at 11/29/2006 10:20:00 AM
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