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000
FXUS62 KRAH 181957
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
257 PM EST Sun Nov 18 2018

.SYNOPSIS...
High pressure will remain over the Mid Atlantic through the weekend.
A cold front will approach the region early next week. A
stronger cold front will cross the area Thursday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 230 PM Sunday...

Near Term: Clouds increasing from multiple directions this afternoon
as cirrus clouds move in from the west and to the south, stratus
associated with a developing wave of low pressure along the South
Carolina coast will be thickening this afternoon and moving into
southern portions of the forecast area later this evening. Short
term models were bullish on rainfall developing with this system as
it approaches and that may eventually be the case overnight but
right now, returns on radar across SC are minimal at best and so it
will take some time for this layer to moisten up to saturation. So
have introduced slight chances into the forecast this evening across
the extreme south and transitioning to the extreme east by Monday
morning. Most areas should remain mostly dry and rainfall amounts
would be a few hundredths to a tenth of an inch at best. Expect fog
and low stratus to play a role again overnight as well, particularly
in the Triad where some lower visibility values could be seen once
again by Monday morning. Temperatures this afternoon are still on
track to top out in the mid 50s to low 60s. Overnight lows will
moderate with the increase in cloud cover with most places in the
lower 40s.

&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 230 PM Sunday...

Short Term: As the coastal wave moves offshore on Monday, taking any
left over precipitation with it, attention will turn to the west as
a cold front approaches the Appalachians. With a very weak surface
low just starting to develop over VA, the main forcing for this
feature will come from the upper level trough which will begin to
dig southward through the Upper Midwest. Without a real good
moisture source, high resolution models are showing precipitation
having a hard time making it over the mountains and drying up with
downsloping surface flow. Therefore will keep conditions dry Monday
afternoon and evening. Temperatures will be warm however as warm air
advection ahead of the front ensues. Expect highs in the lower 60s
with lows Monday night in the low to upper 40s NW to SE.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 300 PM Sunday...

A weak surface cold front will be moving across the area Tuesday
morning with upper level support generally supporting a dry
frontal passage. GFS forecast soundings ahead of the front
are not impressive to say the least. PWATs are only around 0.90"
and there is only a thin saturated layer between 700 and 800 MB.
Behind the cold front a surface high pressure will slowly push
east with CAA starting behind the front Tuesday and continuing
into Thursday. This means each progressive day temperatures will
fall further below normal. By Friday afternoon high temperatures
will only be around 50 degrees (or about 10 degrees below
normal).

The cold air advection mentioned above will be due to a quasi-
stationary long wave trough axis over the eastern United States.
This will allow for multiple cold air intrusions across the
eastern United States. Thursday, a strong upper level low will
amplify over the Hudson Bay, pushing a strong cold front down
into New England. This ~1038 MB high will move through the area
late Thursday into early Friday as a backdoor front. Behind the
front much cooler temperatures are forecast, with low
temperatures Friday morning supposed to be near or below
freezing. The ECMWF continues to advertise the coldest
temperatures with lows in the mid 20s possible, while the GFS
has temperatures near freezing. Either way, temperatures will
be below to possibly well below normal.

Friday afternoon into evening a weak short wave will approach
the area from the west bringing the next chance of
precipitation. The GFS and ECMWF appear to erode the air mass
to quickly with some short of CAD event possible. Have raised
PoPs for Saturday to account for this. Another shortwave is
forecast to move towards the area Sunday, with a wide range of
solutions possible when comparing to the GFS and ECMWF. The most
likely solution for Sunday, as of now, if for a break in the
precipitation with near normal temperatures.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
As of 110 PM Sunday...

24 Hour TAF Period: VFR conditions have finally returned to VFR as
of 18Z after some stubborn fog held on this morning between KRDU and
KGSO. Expect conditions to remain VFR through the daylight hours.
Will have to watch some lower clouds approaching from the south with
an inverted trough that will begin to filter into the vicinity of
KFAY this afternoon, but these are expected to stay above the 3 kft
threshold for MVFR ceilings. During the overnight hours conditions
will start to deteriorate with both ceilings and visibilities
dropping to at least MVFR with some lower IFR/LIFR possible,
particularly in the Triad and extreme southern areas with the
northeastern terminals holding on to VFR the longest. It will take
till the end of the TAF period for VFR conditions to return with the
chance that KFAY and KRDU do not return to VFR by 18Z Monday.

Long Term: Rain should remain east of the major terminals Monday
night but there will be chance for fog and low stratus ahead of a
dry cold front that will move through on Tuesday. High pressure will
moves in for the middle of the week with some clouds increasing by
the end of the week as the high moves into a better position for
cold air damming.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...RAH
NEAR TERM...Ellis
SHORT TERM...Ellis
LONG TERM...Haines
AVIATION...Ellis