PARSONBROWN
Member
Huntsville AFD
So, as mentioned, it now appears that the most likely scenario takes
the core of the strong short wave just to our south as it traverses
the region. This will place the TN Valley region in a more favorable
location for wintry type precipitation, and indeed forecast snowfall
amounts have increased with this forecast package. However, we are
still probably a little conservative with snowfall amounts due to
model output changes and run-to-run inconsistencies. Nevertheless,
the trend is clear, and with better model agreement with the latest
00Z guidance suite on the placement of large scale features, this
lends increasing confidence in snowfall across the area. In addition,
given the latest suite of operational guidance, it appears that some
banding of snow and heavier snowfall rates could occur along a mid-
lvl TROWAL along the northern flank of the upr low. The exact
placement of this feature and the better, enhanced dynamic lift
associated with it are still a bit uncertain, but a reasonable
scenario does place it at least for a time across our southern Middle
TN counties and perhaps along the TN/AL border area. So, there are
still a lot of details to work out and honestly, this will probably
be an ongoing process right up until Sunday.
Anyway, rain appears likely to change over to snow generally from
W-E on Sunday morning and into the early afternoon (although timing
refinement will still occur). Given the prospects for strong dynamic
lift and even convective potential, snowfall rates could be
moderate/heavy along a band north of the low and would be sufficient
to produce accumulating snow. The best chances for this again will
occur along/near the TN border and in southern Middle TN. Current
forecast snowfall amounts there have prompted the issuance of a
Winter Storm Watch, which will go from 06Z Sunday to 00Z Monday.
But, if current model output trends hold, then the Watch may need to
be expanded to other counties in northern AL. Quite a bit of
adjustments were needed for NBM output and forecast highs were
adjusted to between the 10th-25th percentiles for Sunday, which
seemed more fitting given the strong dynamic/column cooling and
precipitation-laden scenario. Temperatures will probably be in the
30s all day, and will likely fall in the afternoon as CAA takes place
and winds back around from the N behind the departing system.
Snowfall may continue into the early evening, especially for eastern
locations. With regards to snowfall totals, we currently have amounts
less than one inch for valley locations in N Alabama, with amounts
ranging from around one inch to 3 inches in TN...and yet higher
amounts on some of the highest elevations of the plateau. But again,
these amounts are really preliminary and significant revisions are
still likely...so keep abreast of the latest forecast updates.
So, as mentioned, it now appears that the most likely scenario takes
the core of the strong short wave just to our south as it traverses
the region. This will place the TN Valley region in a more favorable
location for wintry type precipitation, and indeed forecast snowfall
amounts have increased with this forecast package. However, we are
still probably a little conservative with snowfall amounts due to
model output changes and run-to-run inconsistencies. Nevertheless,
the trend is clear, and with better model agreement with the latest
00Z guidance suite on the placement of large scale features, this
lends increasing confidence in snowfall across the area. In addition,
given the latest suite of operational guidance, it appears that some
banding of snow and heavier snowfall rates could occur along a mid-
lvl TROWAL along the northern flank of the upr low. The exact
placement of this feature and the better, enhanced dynamic lift
associated with it are still a bit uncertain, but a reasonable
scenario does place it at least for a time across our southern Middle
TN counties and perhaps along the TN/AL border area. So, there are
still a lot of details to work out and honestly, this will probably
be an ongoing process right up until Sunday.
Anyway, rain appears likely to change over to snow generally from
W-E on Sunday morning and into the early afternoon (although timing
refinement will still occur). Given the prospects for strong dynamic
lift and even convective potential, snowfall rates could be
moderate/heavy along a band north of the low and would be sufficient
to produce accumulating snow. The best chances for this again will
occur along/near the TN border and in southern Middle TN. Current
forecast snowfall amounts there have prompted the issuance of a
Winter Storm Watch, which will go from 06Z Sunday to 00Z Monday.
But, if current model output trends hold, then the Watch may need to
be expanded to other counties in northern AL. Quite a bit of
adjustments were needed for NBM output and forecast highs were
adjusted to between the 10th-25th percentiles for Sunday, which
seemed more fitting given the strong dynamic/column cooling and
precipitation-laden scenario. Temperatures will probably be in the
30s all day, and will likely fall in the afternoon as CAA takes place
and winds back around from the N behind the departing system.
Snowfall may continue into the early evening, especially for eastern
locations. With regards to snowfall totals, we currently have amounts
less than one inch for valley locations in N Alabama, with amounts
ranging from around one inch to 3 inches in TN...and yet higher
amounts on some of the highest elevations of the plateau. But again,
these amounts are really preliminary and significant revisions are
still likely...so keep abreast of the latest forecast updates.
