Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
1233 PM EST Friday Dec 6 2013
slow moving cold front continues southeast with abundant
precipitation through tonight. Brief high pressure Saturday.
Another wet system Sunday and Monday.
Near term /through tonight/...
1015 am update...significant changes made to grids based on model
output and current radar/obs. Slowed onset of wintry weather
across southeast Ohio as cold air continues to hang just northwest of County Warning Area...and
expect additional wave to keep it nearly stationary into this
Areas of moderate to heavy rain continue on the radar scoop this
morning. Many creeks and small streams are rising rapidly.
However...areas of rain show signs of breaking up and becoming
more scattered in nature...and the rain accumulation should begin
to subside. In the other hand...additional precipitation in the
form of snow will affect southeast Ohio and portions of WV today and
Increased snowfall expected across southeast Ohio and The Lowlands
of West Virginia per westward guidance showing and areas of heavy
snowfall across and west of Perry County. Therefore...issued a
Winter Storm Warning for snow for Perry County as expect 3 to 5
inches...and winter weather advisories for
Vinton...Morgan...Athens and Washington counties in southeast
Ohio through tonight.
Sref probabilities suggest up to 80 percent for snowfall greater
than 4 inches over Perry County and west. Models indicate cold
advection under northwest flow at 850 mb reaching minus 5c by
Used the bias consensus NAM blended with the MOS for temperature
through the period.
Short term /Saturday through Sunday/...
only minor differences with the large scale features in run to run
comparisons of various short term model output. Not much change with
the overall previous forecast for Saturday. Surface front and axis of
deep layer moisture continues to push off to the southeast during
the day Saturday. Precipitation chances will wind down from west to east
during the 12z-18z time frame mainly east of the Ohio River. Drying
in the middle-levels during this time frame suggests the potential for
the end of precipitation to potentially be sleet/freezing rain. This bears
watching of course but amounts should remain on the light side.
Clouds may be slow to break east of the Ohio as usual with continued
cold advection but even here should see some late day partly cloudy
skies. Meanwhile...southeast Ohio zones should see breaks in the clouds by
Things begin to change rapidly overnight Saturday night as surface high
pressure pushes off to our northeast and the next wave of low
pressure rides northeast along the front to our southeast. Temperatures
should fall during the evening hours Sat night into the low/middle 20s
most lowland locations before leveling off as dense cloud cover
moves overhead and wind direction quickly veers from north at 00z
sun to the east by 12z sun. Meanwhile...deep layer moisture prognosticated
to arrive again from south to north between 12z and 18z sun...and as
such have bumped up probability of precipitation to categorical pretty much everywhere
except the northwest zones by 18z sun. Precipitation type at this point
appears to transition from snow to sleet/freezing rain to finally rain by
around the 18z-19z time frame for the crw-heights corridor south into
the coalfields...and for the pkb-ckb area by around 21z. Coded up a
quick half inch to an inch of snow for much of The Lowlands early
Sunday morning prior to the changeover. The northwest zones may
remain in an all snow or wintry mix all day...where these locations
may see a bit more total snow by late Sunday...perhaps around
1.0-1.5 inches. Also...there continues to be a greater concern for a
fairly prolonged freezing rain event for the eastern mountains per
latest guidance from sun middle afternoon into sun evening and into
early overnight Monday. As Sunday afternoon is still five periods
out...opted to not issue any ice highlights due to ongoing
highlights...as well as to allow the day shift to take another look
at the event.
Temperatures on Sunday night will continue to slowly rise during the
overnight hours as moisture continues to flow into the area...have
continued the non-diurnal temperature curve which the previous shift had a
good handle on. A good chance of precipitation will continue during the
overnight hours...but precipitation by early Monday morning should be all
rain except perhaps the far northern reaches of Perry County Ohio and
a few sheltered deep valleys of the eastern mountains. Will also
need to continue to monitor water as well. With precipitation received from
this current round...it may not take too terribly much for flooding
with Sunday and Sunday night/S round.
Long term /Sunday night through Thursday/...
reasonable model agreement with the last in a series of low pressure
systems to affect our area this period. Low center lifts north just
to the west of our area Monday...before sweeping a cold front through
Monday night and ending precipitation. Ahead of the low...stubborn
cold air damming is noted on the models on east facing slopes of the
west virginian mountains...with a good warm surge west of the
mountains Sunday night and Monday. Thus...expect a period of
freezing rain on east facing slopes before changing to all rain
Monday morning. Elsewhere...rain. Amount of quantitative precipitation forecast looks to be possibly
heavy...and will have to watch water problems closely in addition to
current rainfall events. With strong anticyclonic curvature in the
surface high building in behind the system Monday night...Post
frontal snow showers do not look as potent and long lived as one
would think in the cold advection upslope flow. Thus...minor snow
accumulations expected. High pressure builds in Tuesday through
Thursday with dry and cold weather.
Aviation /17z Friday through Tuesday/...
general rule through the night will be IFR ceilings with MVFR to
IFR visibilities as large storm system continues to impact the
region. Should start to see ceilings improve early Saturday
morning across southeast Ohio...then improvement to MVFR at taf sites
during the day Saturday as the system pulls away. This afternoon
precipitation should be mainly rain but then precipitation type becomes a
tough call at time as cold air begins to filter in from the west.
Western taf sites will be the first to change...going from rain to
sleet to snow over a several hour time period. Can not rule out a
very brief period of freezing rain...however pavement with be warm
and wet so should not get any ice accumulation except possibly on
elevated surfaces. Light snow showers will decrease from west to
east Saturday morning.
Forecast confidence and alternate scenarios through 18z Saturday...
Forecast confidence: medium.
Alternate scenarios: timing of categorical and precipitation changes may vary.
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.
UTC 1hrly 14 15 16 17 18 19 20 21 22 23 00 01
EST 1hrly 09 10 11 12 13 14 15 16 17 18 19 20
crw consistency h h h h h h h h h M h M
heights consistency h h h h h h h h h M M M
bkw consistency h h h h M M M M M M M h
ekn consistency h h h h h h h h h h M M
pkb consistency h h h h h h h h h h M h
ckb consistency h h h h h h h h h h h M
After 18z Saturday...
IFR possible Sunday and Monday.
significant rises are occurring/expected on rivers in response to
ongoing...prolonged rain which is expected to last through today.
Rivers that are especially vulnerable include...but are not
limited to -- the Little Sandy including Grayson...the West Fork
including Clarksburg...the little
Kanawha...mud...Pocatalico...Tygart Valley...and Symmes Creek.
Rises are also expected on small creeks and streams that drain
into these larger...main Stem waterways.
Another wet system will effect the region on Sunday and Monday. With
the rivers already running high from the current event...the
threat of river flooding remains...and even increases.
repairs continue at Parkersburg ASOS...and automated observations
may be unavailable.
WV...Flood Watch through Saturday morning for wvz005>011-013>020-
Ohio...Flood Watch through Saturday morning for ohz067-075-076-
Winter Weather Advisory until 1 am EST Saturday for ohz067-075-
Winter Storm Warning until 1 am EST Saturday for ohz066.
Kentucky...Flood Watch through Saturday morning for kyz101>103-105.