Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
250 PM EST Sat Dec 7 2013
high pressure passes north this evening. Warm front lifts north late
tonight with widespread mixed precipitation tonight through Sunday
night. Another system passes south Monday night and Tuesday.
Near term /through Sunday/...
tricky forecast hinged very heavily on temperature profiles tonight
and tomorrow. For this evening...high pressure passes to the
north...and satellite shows clouds breaking up across northwest County Warning Area this
afternoon. Front that passed through over last couple days lifts
north as a warm front tonight into tomorrow...bringing another hefty
dose of precipitation to the forecast area...and especially eastern
half. Initially temperatures surface up through 850mb below 0...so cold
enough to start as snow across the south...with precipitation spreading to
the north through the night. Warm air advection takes over with southerly flow and
begins warming from 850mb down and will see a transition zone
develop and move north. From south to north...will first get sleet
mixing in as warm nose inches north...then transitioning to rain as
warm nose becomes established. For much of the mountains in
WV...surface temperatures will remain at or below freezing through much of
the day...so freezing rain a large threat and have upgraded Raleigh
and Fayette to a Winter Storm Warning...and Webster and Nicholas to
a Winter Weather Advisory. Went with the advisory there because in
these southeast flow events...typically western portions of Webster and
Nicholas warm up...while just extreme eastern portions of the
counties are in the impact zone. Higher elevations will also warm
more quickly as 850 temperatures rise...so have less ice accumulation
across higher ridges.
Models in good agreement on this warming aloft...however subtle
difference create discrepancies on just when snow changes to
rain...which in turn has a large impact on icing potential. GFS is
the fastest bringing 0c line north...followed by European model (ecmwf) then the NAM
and rap. However...European model (ecmwf) never gets as warm as other models. Went
with a blend of GFS and NAM to depict the warm nose through middle
morning...and then switched to NAM only which has higher detail with
On the liquid precipitation side of things...additional rain falling on
already soggy ground leads to concerns about potential
flooding...and have Flood Watch going into the short term forecast
Have non-diurnal temperature curve starting around 06z tonight...as
gradual warming moves in from the south and at higher elevations of
the northern mountains. Used the cooler mav as a starting point for
hourly temperatures during the non-diurnal period.
Short term /Sunday night through Tuesday/...
no significant changes were made since previous forecast.
Precipitation will be ongoing at the beginning of the period..with
another wave of low pressure riding northeast into the area Sunday
night...bringing a brief period of enhanced precipitation to the
region. Warmer air will continue to move into the region during the
day and night Sunday...eventually eroding enough of the cold air in
place across the mountainous counties...that freezing rain should
change over to all rain by late Sunday night/early Monday. Still
though...expecting up to another tenth of an inch or so of ice
across mountain zones...particularly eastern slopes. Will probably
go ahead and issue another Flood Watch across areas that received
the heavier rain on Thursday and Friday. Although quantitative precipitation forecast wont be as
great...and precipitable water values expected to top out at only around an inch or
so...with many area creeks and streams running high...along with
waves enhancing precipitation at times...will err on the side of
Bulk of precipitation will taper off later in the day Monday as cold
frontal boundary sinks south across the region...and stalls out to
the south. Another wave will ride north along this boundary on
Tuesday. Still plenty of uncertainty concerning track/westward
extend of moisture associated with this disturbance...so for
now...just held onto chance probability of precipitation...particularly across the eastern
half of the County Warning Area. Regardless...should have enough cold air in place
that bulk of precipitation will be in the form of snow on Tuesday.
High pressure will start to nudge in from the west later Tuesday
evening...with gradually drying...and clearing weather.
Long term /Tuesday night through Saturday/...
Canadian high pressure finally takes control Tuesday and lasts the
remainder of the work week...under dry west to northwest flow aloft.
This will bring lots of sunshine but cold temperatures through middle
week...then a slow warming trend into the 40s by Friday as the high
center slides east of the area. With dry air in place and lack of
clouds...expect large diurnal ranges in temperatures this
week...bringing quite cold nights.
Aviation /20z Saturday through Thursday/...
precipitation has ended across County Warning Area for now...as IFR ceilings are
gradually improving to MVFR...and expect continued improvement to
VFR across much of County Warning Area through the afternoon as high pressure
quickly moves in and then back out. One exception is bkw where
northerly flow has fog and low stratus penned in for now. Do
expect this to improve...but remain MVFR ceilings into tonight.
Surface wave moves north tonight into tomorrow...pushing cold
front back north as a warm front and bringing renewed precipitation to
the forecast area. This precipitation should start as snow...with IFR
visibilities and dropping ceilings. As warmer air moves in...precipitation type
will transition to sleet then rain with MVFR visibilities and MVFR
to IFR ceilings. Issue becomes surface temperatures...and could get a
good dose of freezing rain in mountain valleys...including bkw.
Other southern sites...crw and heights...should warm up enough for
just rain and/or sleet...while northern sites are expected to
remain mostly snow and sleet. However...trends will need to be
monitored for small scale temperature issues which may complicate
Forecast confidence and alternate scenarios through 18z Sunday...
Forecast confidence: medium.
Alternate scenarios: timing of ceiling improvements today may vary.
Timing of Cat drops tonight...and p-type changes may vary tonight
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 20 21 22 23 00 01 02 03 04 05 06 07
EST 1hrly 15 16 17 18 19 20 21 22 23 00 01 02
crw consistency h h h h h h h h h h h h
heights consistency h h h h h h h h h h h h
bkw consistency h h h h h h h h h h h h
ekn consistency M h h h h h h h h h h h
pkb consistency h h h h h h h h h h h h
ckb consistency h h h h h h h h h h h h
After 18z Sunday...
IFR expected to linger into at least Sunday night. IFR possible
again Monday night into Tuesday in snow.
runoff is beginning to slow across the County Warning Area...and
most rivers have or will soon crest. Flood warnings still in
effect along portions of the Elk...Buckhannon...and Tygart Valley
In addition...more rainfall is expected Sunday into Sunday
night...which may cause additional rises on rivers...especially in
West Virginia zones. This additional rain may also cause flooding
along small creeks and streams. Flood Watch posted for Sunday
afternoon into Monday afternoon.
additional parts for Parkersburg ASOS are expected to arrive Monday.
Automated observations will be unavailable at times until then.
WV...Flood Watch from Sunday afternoon through Monday afternoon for
Winter Weather Advisory from 4 am to 7 PM EST Sunday for
Winter Storm Warning from 4 am to 7 PM EST Sunday for wvz035-
Winter Storm Warning from 4 am Sunday to 4 am EST Monday for
Kentucky...Flood Watch from Sunday afternoon through Monday afternoon for