Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
939 PM EST Sat Dec 20 2014
weak disturbance exits tonight. Weak high pressure crosses Sunday.
Middle level shortwave clips mountains Monday. Strong low pressure system
lifts northeast across the Ohio Valley through Christmas evening.
Near term /through Sunday/...
9:30 PM update...not too many changes made to the current
forecast. Updated earlier to add a few snow flurries by Beckley.
Don/T think there is much left touching the ground on the west
side of the mountains. Have noticed several hours of light snow at
Bluefield. Expect a solid stratus deck across the area overnight
with the shortwave. The current forecast has things covered well.
middle level baroclinic Leaf over the area early this afternoon
drifts east-northeastward out of the area tonight as an upper level short wave trough
crosses. Weak high pressure settles into the forecast late tonight
beneath upper level ridging in the wake of the short wave trough...and
then begins drifting east-northeastward out of the area Sunday afternoon...as
the upper level flow starts to back to the SW.
Low level moisture remains in place at persistent 800 mb-9 inversion
although the stratocu had broken up across most of WV. With little
flow to work with...this is likely to reform tonight or at the
latest first thing Sunday morning on mixing. Daytime mixing will
eventually lead to a more cellular cumulus field Sunday afternoon with a
significant decrease in cloud amount by the end of the day Sunday.
Lows looked good in light of latest guidance for tonight although
bias corrected values were higher. Continuing the trend of lower
highs with another day of stratocu for Sunday. The late day
clearing should still allow temperatures to break 40 across much of
Short term /Sunday night through Tuesday/...
middle level ridge axis crosses Sunday night bringing a drier air
mass to the area. However...BUFKIT soundings suggest upper level
clouds will blanket the area...with low level stratus forming
along the western slopes and eastern mountains Sunday night into
Models indicate a developing weak surface low pressure along the
southeast coast...meanwhile...at the middle levels...a weak shortwave
crosses the area on Monday. These two systems could squeeze some
moisture across the eastern mountains and produce low chance for
precipitation there. Expect light rain...with pockets of light
freezing rain where temperatures could remain at or below
freezing...and some light snow with this scenario. Temperatures
across The Lowlands will be in the upper 30s Monday night.
The weak middle level wave could bring light precipitation across southeast Ohio
by Tuesday. Increased probability of precipitation to high chance across southeast Ohio
and southern WV where models show some agreement in their quantitative precipitation forecast
Weak flow becomes gentle to moderate from the south and southeast
from the surface to h850...to bring warm air advection. Therefore...temperatures
will be a bit warmer than the past few days. Generally...highs on
Monday could reach into the middle 50s...and into the lower 60s on
Tuesday as warm air advection becomes stronger.
Long term /Tuesday night through Saturday/...
active weather pattern continues in the long term period...with a
deepening upper trough across the Central Plains at the beginning of
period...with a surface low moving northeast out of the Gulf states
towards the region. Strong southerly winds will develop out ahead of
the system...with good moisture transport into the area as a result.
This is a strong system...with strong pressure falls/bombogenesis as
the low moves towards the region. Cold front still prognosticated to move
through the area Wednesday...with falling temperatures...strong
gusty winds along and behind the front due to tight pressure
gradient...and potential for strong winds aloft to mix down...and even a
slight chance for thunder...mainly across the west...as the front
moves into the region. Starting to look more and more like winter
precipitation will not be a huge hazard with this system...due to
the overall speed...and the fact that by the time enough cold air is
in place...bulk of moisture should have exited. In addition...still
quite a bit of uncertainty as to how much will actually be able to
stick to the ground if ground temperatures are too warm as
temperatures will rise into the 50s out ahead of the system.
However...will still see a change over to snow Wednesday night into
Thursday...along with falling temperatures. Will continue to
maintain severe weather potential statement.
On Thursday...upper low lifts north across Canada...becoming nearly
stacked with surface low. Still a chance for some light snow shower
activity on Thursday...but will gradually see a drying trend from
south to north as the system pulls away.
Another front approaches late in the extended.
Aviation /03z Sunday through Thursday/...
ckb observation missing since 13z on account of a comms issue which
is being investigated...issued taf with amend not schedule.
Expect the stratocu deck to return overnight and will be slow to
break up tomorrow. Expect clearing after 20z. Believe it will be
Surface flow will remain calm to light and variable...while light west
to SW flow aloft will be most werly Sunday morning.
Forecast confidence and alternate scenarios through 00z Monday...
Forecast confidence: low to medium on the timing and placement of
the stratus deck...high otherwise.
Alternate scenarios: timing of the stratus deck retreating nwwd
early on and then returning / reforming overnight tonight could
Experimental table of flight category objectively shows consistency
of weather forecast office forecast to available model information:
h = high: taf consistent with all models or all but one model.
M = medium: taf has varying level of consistency with models.
L = low: taf inconsistent with all models or all but one model.
Date sun 12/21/14
UTC 1hrly 02 03 04 05 06 07 08 09 10 11 12 13
EST 1hrly 21 22 23 00 01 02 03 04 05 06 07 08
crw consistency h h h h M M M M M M M M
heights consistency M M M M M M M M M M M M
bkw consistency h h h M M M M M M M M M
ekn consistency h h h h M M M M M M M M
pkb consistency h h h h h h h M M M M M
ckb consistency h h h M M M M M M M M M
After 00z Monday...
IFR possible in mountains late Sunday night and Monday in a wintry
mix. IFR possible in rain Tuesday night into Wednesday...changing to
snow showers late Wednesday...as an intense low pressure center