Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Jackson Kentucky
337 am EST Sat Nov 22 2014
Short term...(today through sunday)
issued at 337 am EST Sat Nov 22 2014
The latest surface map features a large area of high pressure across
the eastern Continental U.S....with low pressure cruising through Ontario.
Aloft...fairly progressive flow is in place...with a weaker short
wave moving through the Ohio Valley. A stronger vorticity is rotating
along northern Mexico...while additional short wave energy is moving
across the Pacific northwest.
Another chilly night has been on tap for eastern Kentucky...although
not as cold as last night. There are a few valleys in the far east
remaining in the upper teens...while low to middle 20s are common in the
broader valleys. Ridgetops are in the 30s thanks to light south to
southeast winds. A decent 850 mb jet has developed across the Ohio Valley
overnight...with light precipitation breaking out across most of
Indiana and down into western Kentucky. The latest hrrr may support a
few sprinkles across the I-64 corridor towards dawn...however given
the dry air in place chances of measurable precipitation look low.
Once the sprinkles skirt by to the north early this morning...dry
conditions will remain in place thanks to low level southeasterly
flow. Highs today will approach the 60 degree mark in
places...temperatures that we have not seen in about a week and a
half. Meanwhile...northern stream short wave energy will traverse the
U.S./Canadian border...while the southern stream vorticity continues to
slide east. The vorticity will then swing more northeast...reaching the
Tennessee Valley by late in the day on Sunday. This will result in
surface low pressure organizing across the plains...eventually
conglomerating across the Ohio Valley late in the period.
Eastern Kentucky will enjoy a milder night tonight...as warm air
advection continues out ahead of the approaching system from the
west. Lows will bottom out in the lower 30s in the more sheltered
valleys in the east...while other locations will see upper 30s and
lower 40s. A warm front/mid-level short wave will approach the area
from the southwest on Sunday...with widespread shower activity
breaking out across eastern Kentucky in the afternoon. Have continued
to downplay the quantitative precipitation forecast amounts in the far east with downslope flow in
place. Despite the showers moving in...highs will make it back into
the upper 50s and lower 60s.
Long term...(sunday night through friday)
issued at 337 am EST Sat Nov 22 2014
Still some question as to how fast the trough axis shifts to the
north Sunday evening. GFS is much more progressive on bringing the
dry slot in quickly Sunday evening...while the European model (ecmwf) holds it back
early on. Basic thinking is that even if the dry slot moves in
faster...we may still get development into the warm sector through
the night or possibly even some measurable drizzle. Thus...will
maintain high chance to likely probability of precipitation through the first half of the
night...with drizzle becoming more likely as the night progresses.
On Monday...a sharp cold front will push into and cross the area.
This should again bring higher chances for showers as it crosses the
area through early to middle afternoon. In the wake of the
front...temperatures will take a tumble in the afternoon and evening
hours. After climbing into the low 60s...temperatures by the evening
should settle back into the 40s. Still looks like a windy day...with
925mb winds topping 35 knots as the front crosses the area. Any
shower activity may actually help to mix down some isolated higher
gusts to 40 or 45 miles per hour.
Surface high pressure should move into the Ohio River valley Monday
night with dry weather returning. Attention will then turn to a
possible noreaster as an area of low pressure moves up the eastern
US coast. 00z European model (ecmwf) has shifted the track of this low back to the
west...bringing moisture into the Appalachian Mountains. Going to
maintain the dry forecast...but if this system trends any farther
west...may need to insert some probability of precipitation by Wednesday.
Models really diverge thereafter as we head into Thanksgiving day.
GFS builds a ridge over the Ohio River valley...suggesting
temperatures may reach into the 50s...while the European model (ecmwf) digs out
another sharp trough and would put temperatures more into the 30s
with a good chance for snow. Clearly this is a large difference in
the models...and puts lots of uncertainty on the Thanksgiving
forecast and beyond. For now...will go with a compromised
forecast...with a slight edge towards the colder European model (ecmwf) as it has
been very consistent on the colder solution. Will also maintain low
probability of precipitation Wednesday night into Thursday night...and go with a mixture of
rain/snow through this period. It does look regardless of
Thanksgiving day...models point to a much colder end to the
week...with temperatures staying well below normal into Friday and
Saturday. We should see drier weather for Friday and Saturday.
Aviation...(for the 06z tafs through 06z Saturday night)
issued at 105 am EST Sat Nov 22 2014
Besides some passing cloud cover from time to time...mainly at or above
10k feet above ground level...VFR conditions will reign through the period. Winds
will remain out of the south and southeast...remaining at or around 5
kts through the period.