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Wintry More SE Snow ? (1/16-1/18)

If I were in NE GA, I would be absolutely pissed right now. That snowhole is there in some form with a lot of guidance.
 
Shawn said:
If I were in NE GA, I would be absolutely pissed right now. That snowhole is there in some form with a lot of guidance.
Click to expand...

Seems like the models are trying to connect the expansion on precip over the Carolinas into the expansion over East AL-thrust Central GA...aligns with what Simmons was referring to with the jet streak.


Sent from my iPad using Tapatalk
 
meanwhile at the MRX funky bunch ranch:
DualImage.php


* WHAT...Snow is expected. Plan on slippery road conditions,
including during the evening commute. Total snow accumulations
of 1 to 3 inches are expected.

* WHERE...Portions of East Tennessee.

* WHEN...Until 7 PM EST /6 PM CST/ this evening.
 
Flo said:
Are temps going to be an issue?
Click to expand...

Likely. It's a timing thing. The new discussion sounds about right until we get more information from today's guidance and see what is happening to our West:

CAE:

An positively tilted upper level trough over the Great Lakes
and Mid Mississippi Valley will shift east and become more
amplified by this evening. This will push a cold front
currently extending from WV through the Tennessee Valley to
southeast Texas into the forecast area during the predawn hours
Wednesday. Moderate 500mb height falls resulting from the
amplifying trough will result in increasing dynamical forcing
over the frontal boundary during the 09z-18z time frame. There
is not much issue with the upper forcing with this short lived
event, however moisture is somewhat limited with precipitable
water values increasing to around 0.6-0.7 inches in a narrow
zone just ahead of the frontal boundary. Have increased pops to
high chance and likely across the northern part of the forecast
area with lower chance pops across the CSRA and southeast
Midlands with the highest pops focused on the 09z-15z time
frame. QPF is another uncertain factor with all model guidance
showing generally light amounts and ensemble guidance ranging
from no QPF to as much as a quarter inch liquid accumulation
leading to more uncertainty and adding to the complexity of this
forecast.

A look at model time heights show the best moisture is below the
favored dendritic snow growth although there is some moisture
available for a short period of time. Forecast soundings indicate
the surface and near surface layers remain above freezing or
cool to right around freezing as the front pushes through the
region and there could be a few hour period where precipitation
occurs initially as rain or a rain snow mix and then changing
over to snow as the deeper moisture is shifting out of the area.
So the key to this event will be how long will the moisture be
within the snow growth zone when there is significant lift
occurring and can the near surface layer get cold enough to
support accumulating snowfall. Ground temperatures are another
limiting factor with observed soil temps in the 40s today and
with max temperatures today expecting in the 50s which should
help those soil temps warm a bit further. Also, this type of
event where there is the lack of a strong surface low off the
coast helping bring moisture in from the atlantic and the cold
air is chasing the deeper moisture historically does not favor
accumulating snowfall for high impact events.

All in all, can see a scenario where there is a brief
changeover to snow for a period of time long enough to
accumulate up to an inch of snow possibly in the far northern
Midlands of Lancaster and Chesterfield counties, although
confidence remains low due to factors mentioned above. Further
south, would not be surprised to see some snow flakes across the
central Midlands but am not confident it would occur long
enough after the changeover to accumulate much more than a
dusting if that. After coordination with RAH/GSP/ILM, have
decided to post winter weather advisory for an inch or less of
snow accumulation in Lancaster and Chesterfield, an area where
confidence is highest.
 
Shawn said:
Likely. It's a timing thing. The new discussion sounds about right until we get more information from today's guidance and see what is happening to our West:

CAE:

An positively tilted upper level trough over the Great Lakes
and Mid Mississippi Valley will shift east and become more
amplified by this evening. This will push a cold front
currently extending from WV through the Tennessee Valley to
southeast Texas into the forecast area during the predawn hours
Wednesday. Moderate 500mb height falls resulting from the
amplifying trough will result in increasing dynamical forcing
over the frontal boundary during the 09z-18z time frame. There
is not much issue with the upper forcing with this short lived
event, however moisture is somewhat limited with precipitable
water values increasing to around 0.6-0.7 inches in a narrow
zone just ahead of the frontal boundary. Have increased pops to
high chance and likely across the northern part of the forecast
area with lower chance pops across the CSRA and southeast
Midlands with the highest pops focused on the 09z-15z time
frame. QPF is another uncertain factor with all model guidance
showing generally light amounts and ensemble guidance ranging
from no QPF to as much as a quarter inch liquid accumulation
leading to more uncertainty and adding to the complexity of this
forecast.

A look at model time heights show the best moisture is below the
favored dendritic snow growth although there is some moisture
available for a short period of time. Forecast soundings indicate
the surface and near surface layers remain above freezing or
cool to right around freezing as the front pushes through the
region and there could be a few hour period where precipitation
occurs initially as rain or a rain snow mix and then changing
over to snow as the deeper moisture is shifting out of the area.
So the key to this event will be how long will the moisture be
within the snow growth zone when there is significant lift
occurring and can the near surface layer get cold enough to
support accumulating snowfall. Ground temperatures are another
limiting factor with observed soil temps in the 40s today and
with max temperatures today expecting in the 50s which should
help those soil temps warm a bit further. Also, this type of
event where there is the lack of a strong surface low off the
coast helping bring moisture in from the atlantic and the cold
air is chasing the deeper moisture historically does not favor
accumulating snowfall for high impact events.

All in all, can see a scenario where there is a brief
changeover to snow for a period of time long enough to
accumulate up to an inch of snow possibly in the far northern
Midlands of Lancaster and Chesterfield counties, although
confidence remains low due to factors mentioned above. Further
south, would not be surprised to see some snow flakes across the
central Midlands but am not confident it would occur long
enough after the changeover to accumulate much more than a
dusting if that. After coordination with RAH/GSP/ILM, have
decided to post winter weather advisory for an inch or less of
snow accumulation in Lancaster and Chesterfield, an area where
confidence is highest.
Click to expand...
After reading that I'll stick to nada for Irmo and Lexington..
 
Flo said:
After reading that I'll stick to nada for Irmo and Lexington..
Click to expand...

They have no reason to add any kind of advisories or panic to the area at this point. It doesn't mean it won't happen, but if they put in what new guidance says, they will cause a lot of panic that could cause a whole lot of problems around here.

Right now they say 0.5 inch. in the forecast for Lexington. That's smart.
 
Hmmm FFC Running "late" with their AFD.. Guess a lot of thought/work going into it.. Since they ve expanded WWA Area few hours ago
 
426
FXUS64 KBMX 160918
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
318 AM CST Tue Jan 16 2018

.SHORT TERM...
Today and tonight.

The Arctic front has moved into Northwest Alabama and will be making
its way through the forecast area this morning and afternoon. A band
of heavy snow is currently ongoing in eastern Arkansas and western
Tennessee. The eastern edge of this band should reach our
northwestern CWA border around 12z, likely with less intensity than
currently observed. Models are in general agreement with the idea of
a weakening band in the QPF output, but a swath of 700mb RH values
near 100% appears healthy across the entire CWA along with
saturation through the column. This system has been overperforming
across the Memphis and Paducah areas, and with that in mind, we have
raised accumulations across the entire area to the 1 to 1.5 inch
range. A relative minimum seems likely somewhere in the CWA as the
isentropic lift takes a pause before lift increases in association
with the upper-level trough. This minimum may actually occur
across the northwestern part of the area, and the focus could
shift to a second wave farther east in the afternoon and evening.

The approaching vort max at 500mb appears very impressive this
afternoon into tonight and will have an opportunity to enhance the
snow band as it moves east of I-59. PWAT values will surge in this
zone, and additional lift could result in snowfall amounts exceeding
our current forecast. The ECMWF, several European Ensemble members,
and the Regional Canadian indicate the potential for 2-4 inch
amounts along and east of I-59 all the way to our eastern and
southern borders. This scenario will be monitored for a possible
upgrade to a Winter Storm Warning. Impacts could be significant
across our entire forecast area due to temperatures falling into
the 20s and teens as the snow falls. A Wind Chill Advisory has
been issued for the entire area for tonight and Wednesday morning
for wind chills of 5 above zero to 5 below zero.

87/Grantham
 
Gfs, finally joining the party outright into the Carolinas. Whew.

Still playing catchup, though. ;)
 
Claycochaser said:
426
FXUS64 KBMX 160918
AFDBMX

Area Forecast Discussion
National Weather Service Birmingham AL
318 AM CST Tue Jan 16 2018

.SHORT TERM...
Today and tonight.

The Arctic front has moved into Northwest Alabama and will be making
its way through the forecast area this morning and afternoon. A band
of heavy snow is currently ongoing in eastern Arkansas and western
Tennessee. The eastern edge of this band should reach our
northwestern CWA border around 12z, likely with less intensity than
currently observed. Models are in general agreement with the idea of
a weakening band in the QPF output, but a swath of 700mb RH values
near 100% appears healthy across the entire CWA along with
saturation through the column. This system has been overperforming
across the Memphis and Paducah areas, and with that in mind, we have
raised accumulations across the entire area to the 1 to 1.5 inch
range. A relative minimum seems likely somewhere in the CWA as the
isentropic lift takes a pause before lift increases in association
with the upper-level trough. This minimum may actually occur
across the northwestern part of the area, and the focus could
shift to a second wave farther east in the afternoon and evening.

The approaching vort max at 500mb appears very impressive this
afternoon into tonight and will have an opportunity to enhance the
snow band as it moves east of I-59. PWAT values will surge in this
zone, and additional lift could result in snowfall amounts exceeding
our current forecast. The ECMWF, several European Ensemble members,
and the Regional Canadian indicate the potential for 2-4 inch
amounts along and east of I-59 all the way to our eastern and
southern borders. This scenario will be monitored for a possible
upgrade to a Winter Storm Warning. Impacts could be significant
across our entire forecast area due to temperatures falling into
the 20s and teens as the snow falls. A Wind Chill Advisory has
been issued for the entire area for tonight and Wednesday morning
for wind chills of 5 above zero to 5 below zero.

87/Grantham
Click to expand...


Let’s hope he’s right, because some of the model output for N AL looked awful.
 
Scary wording from HUN:
The forecast through the rest of the day remains challenging as
several factors may work against parts of the TN Valley and cause
little to no snow to be observed across portions of the area. As
stated above, the snow will not quite reach the area until just
before daybreak, per hires guidance, and then slowly shift eastward
through the day. These hires models also indicate that the snow band
will generally diminish as it crosses into the central portion of
the forecast area, before it redevelops across the southeast. One
caveat to this is how poorly models have handled the current band of
snow. With observed totals exceeding 3 inches in some areas of
western Tennessee, am generally inclined to believe that the models
are also overdoing the drying trend over the forecast area. However,
as the upper level jet becomes more oriented in a north- south
direction and lifts to the north, we may lose out on the enhanced
lift aloft. Despite this weakening trend of the lift/snow band, most
of the area should still see snow totals up to 0.5 inch, with areas
across NW Alabama, and southern Middle Tennessee possibly exceeding 1
inch before the band weakens as it shifts southward
 
Stormlover said:
Scary wording from HUN:
The forecast through the rest of the day remains challenging as
several factors may work against parts of the TN Valley and cause
little to no snow to be observed across portions of the area. As
stated above, the snow will not quite reach the area until just
before daybreak, per hires guidance, and then slowly shift eastward
through the day. These hires models also indicate that the snow band
will generally diminish as it crosses into the central portion of
the forecast area, before it redevelops across the southeast. One
caveat to this is how poorly models have handled the current band of
snow. With observed totals exceeding 3 inches in some areas of
western Tennessee, am generally inclined to believe that the models
are also overdoing the drying trend over the forecast area. However,
as the upper level jet becomes more oriented in a north- south
direction and lifts to the north, we may lose out on the enhanced
lift aloft. Despite this weakening trend of the lift/snow band, most
of the area should still see snow totals up to 0.5 inch, with areas
across NW Alabama, and southern Middle Tennessee possibly exceeding 1
inch before the band weakens as it shifts southward
Click to expand...
not scary so much as those dudes know what's up.. smart guys.
 
purely diurnal snows, even in Jan, are always a funky bizness in the south.
 
NWS in Birmingham seems rather confident than what most models are showing in regards to accumulation. They must believe it’ll overperform as well. They are saying widespread 1-1.5 inches. Interesting
 
Parker said:
NWS in Birmingham seems rather confident than what most models are showing in regards to accumulation. They must believe it’ll overperform as well. They are saying widespread 1-1.5 inches. Interesting
Click to expand...
And mentioned a possible upgrade to a warning later...
 
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