Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 092346
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
646 PM EST Fri Dec 9 2016

.SYNOPSIS...
Canadian high pressure settles over the Mid-Atlantic tonight into
Saturday, before sliding offshore Sunday. A warm front will lift
through the region Sunday night as low pressure moves into the Great
Lakes. This area of low pressure will push north of the area Monday,
with the associated cold front crossing the region late Monday.
Another strong cold front impacts the region during the middle of
next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
The current surface analysis shows large sprawling
1046mb arctic high pressure centered across nrn AB/SK and extending
through the Northern Plains of the US. An extension of the high has
broken off over the Mid-Mississippi Valley this aftn with the
associated airmass spilling over the mountains. This continual CAA
has held temperatures in the upper 30s to low 40s as 850mb
temperatures have dropped to around -10C. This area of high pressure
builds into the region tonight. By this point the airmass will have
modified enough to lose its arctic characteristics, dewpoints in the
teens locally. Still cold and well below normal nonetheless, with
lows tonight in the upper teens to low 20s inland, to the low/mid
20s for se coastal locations.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Cold high pressure (~1032-1034mb) remains over the area
Saturday through Saturday night. This will result in limited mixing
during the daylight hours Saturday and will keep highs in the upper
30s to low 40s under a sunny sky. A nrn stream trough dives into the
Great Lakes region, which could result in increasing high clouds
late, especially across the north. There should still be several
hours of rather ideal radiational cooling conditions and lows should
once again drop at into the upper teens/low 20s, with 25-30F for
coastal se VA/ne NC.

This initial wave shears out and pushes north of the region Sunday
with as a more potent wave dives into the upper Midwest. The surface
high slides offshore, but warming will be tempered by limited mixing
and increasing clouds. Forecast highs will still be below normal and
moderate only into the mid 40s to around 50 se.

The vigorous nrn stream wave dives through the Great Lakes Sunday
night and a srn stream wave precede it and pushes through the
Tennessee Valley. This will result in a warm front lifting through
the Mid-Atlantic. Sunday night lows will likely occur during the
evening hours, ranging from the mid 30s nw to the low/mid 40s se.
Clouds thicken and lower, with PoPs actually increasing along the
coast initially as some semblance of a coastal trough pushes newd
ahead of the approaching system and interacts with the warm front.
No frozen pcpn is expected at this time across the far nw Piedmont
counties as temperatures are expected to remain above 32F and slowly
rise once any pcpn arrives from the nw later Sunday night.

The srn stream wave tracks across the region through midday Monday,
with the nrn stream wave moving toward the Saint Lawrence Valley by
aftn, which will push the associated cold front into the area.
Forecast PoPs are highest from morning through mid-aftn. Deep-
layered wsw flow will limit QPF, which at this time is forecast to
be aob 0.3". Milder with highs ranging from the mid 50s nw to the
mid 60s se.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
A cold front associated with low pressure tracking along the
St Lawrence River Valley and srn Ontario is expected to cross the
region Mon evening and exit the coast by Tue morning. Although
sw winds should be breezy ahead of the approaching front, the
cooler air behind it is much more modified and n winds are expected
to diminish Mon night into Tue morning as weak sfc high pressure
moves quickly into the region. Onshore/ne winds develop Tue aob
15kt under partly sunny skies. The high slides offshore by Tue
evening as a low pressure system developing over the TN Valley
advances newd twd the Carolinas and Mid Atlantic Region...impacting
the entire forecast area on Wed. Another blast of colder arctic
air is possible very late Wed night into Thu. Overall, temps will
be at to slightly below normal Mon night through Wed night...
becoming much colder Thu (-1 Std Dev) with highs in the upper
30s nw to lower 40s se.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
A clear sky and northwest winds will prevail during the 00Z TAF
period with high pressure in control. Gusty winds that were present
during the afternoon have diminished to around 5 knots and are
expected to average less than 10 knots on Saturday. A few gusts to
around 12 to 15 knots could occur at SBY Saturday afternoon. Also at
SBY...few to sct mid level clouds off the Great Lakes may show up
from time to time.

OUTLOOK...High pressure slides offshore on Sunday. There will be a
chance for rain Monday as a cold front approaches from the west.
Following the passage of the cold front Monday night, dry weather
returns for Tuesday. A chance of rain returns to the forecast
Wednesday as another cold front approaches.

&&

.MARINE...
Sfc high pressure continues to build into the area tonight
through Sat night. Meanwhile, a secondary surge in wnw winds
is occurring this aftn and is expected to persist into this
evening before cold air advection processes subside and a
strong jet streak exits the region along with the base of a
500mb trough. SCA flags in effect for all waters except
Currituck Sound; end times range from midnight through early
Sat morning (a few hours before sunrise). Waves 3-4ft...
subsiding to 2-3ft late this evening. Seas 4-5ft...subsiding
to 3-4ft early Sat morning.

The building sfc high slides overhead Sat night into Sun morning
with light and variable winds. The high then slides offshore by
Sun aftn/early evening and winds become more s-se aob 15kt. The
combination of a weak coastal trough developing along the
Southeast Coast Sun night and a warm front lifting north through
the area should bring rain up along the Mid Atlantic coast late
Sun night into Mon morning with a period of dry conditions
possible over the waters the rest of the day on Mon. Seas average
2-3ft/waves 1-2ft. A cold front associated with low pressure
tracking along the St Lawrence River Valley and srn Ontario is
then expected to cross the waters Mon evening and exit the coast
by Tue morning. Sw winds now forecast to be a tad stronger ahead
of the approaching front, and SCA conditions may be possible
during the day Mon (15-20kt Ocean/Bay/Sound...10-15kt Ern VA
Rivers...4-5ft seas nrn coastal waters). The cooler air behind
the cold front is much more modified and n winds are expected to
diminish Mon night into Tue morning as weak sfc high pressure
moves quickly into the region. Onshore/ne winds develop Tue aob
15kt. The high slides offshore by Tue evening as a low pressure
system developing over the TN Valley advances newd twd the
Carolinas and Mid Atlantic Region...impacting the waters on Wed.
Seas average 2-4ft Tue through Wed/waves 1-2ft.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until midnight EST tonight for ANZ635>638.
     Small Craft Advisory until 4 AM EST Saturday for ANZ630>632-
     634-650-652-654-656-658.

&&

$$
SYNOPSIS...AJZ/SAM
NEAR TERM...AJZ/SAM
SHORT TERM...AJZ/SAM
LONG TERM...BMD
AVIATION...AJB/LSA
MARINE...BMD



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