Area Forecast Discussion
Issued by NWS Wakefield, VA
FXUS61 KAKQ 211759
Area Forecast Discussion
National Weather Service Wakefield VA
159 PM EDT Fri Oct 21 2016
A cold front will mainly cross the area this afternoon into early
this evening. Breezy northwest winds will develop later tonight
and continue through Saturday. Otherwise, cool and more seasonable
conditions will persist tonight through next week.
.NEAR TERM /THROUGH TONIGHT/...
A vigorous upper trough digs over the Ohio Valley today and
effectively slows the ewd progression of the approaching sfc
low/cold front expected to cross the area today. Have delayed the
onset of precip in wrn portions of the area until later this
morning/early aftn once isentropic lift begins to enhance precip
generation along the frontal boundary. Although ample vertical and
directional shear is present across the region today, cross
sections continue to show a lack of lift/omega aloft (much less
through the hail growth zone) with a 100kt jet streak still
located well behind the cold front. Therefore no mention of
thunder remains based on latest model analysis. Despite the slower
start to precip, expect rainfall to increase from west to east
through this aftn/early evening. Overall storm total precip values
totals will be rather light... still ranging from 0.10-0.30 inches
(highest amounts across the north where the better dynamics are
located closer to the parent low). Rain comes to an end tonight
within an hour or two of the frontal passage as a cold Canadian
high builds into the region behind the front. Meanwhile, a coastal
low NNE of the Bahamas (possibly becoming a tropical cyclone)
slowly tracks northward...staying well offshore. The interaction
of the passing cold front with the coastal low (they are expected
to merge tonight) and the incoming cold Canadian high pressure
will significantly tighten the sfc pressure gradient beginning
this aftn. Strong W-NW winds will develop quickly this evening...
mainly due to the strong upper trough swinging through the area
(accompanied by a 100kt jet streak) and strong cold air advection
occurring as well. Winds will be highest along the coastal areas
of Ches Bay and the Atlantic Ocean where sustained winds will
average 20-25 mph with gusts of 30-35 mph. Gusts may be as high as
40 mph along coastal areas of the Nrn Neck and MD/VA Eastern
Shore. Will highlight these areas within the HWO. Farther inland,
gusts will average 20-25 mph.
Temperatures will be at to about 5-7 degrees above seasonal
normals with highs in the mid-upper 70s (low-mid 70s beaches).
Once cold air advection processes commence tonight, temps will
plummet to more seasonal values with lows in the mid-upper 40s
(around 50 degrees far sern coastal areas). Thankfully, the
well-mixed environment tonight will keep lows from dropping to
their fullest potential.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Strong upper trough swings into the region on Saturday and exits
the region Saturday night. A tight sfc pressure gradient, strong
cold air advection, and strong jet streak nosing through the area
on the back side of the upper trough (100-120kt) will all
contribute to the following conditions for Saturday:
1. Strong W-NW winds persisting through Saturday. Sustained winds
across the area will average 20-25 mph. At the coast, expect wind
gusts of 30-40 mph. Farther inland, gusts will average 25-30 mph.
2. Much cooler temperatures that will run 5-10 degrees below
normal. Expect highs in the lower 60s. And near normal lows
Saturday night in the low-mid 40s (45-50 possible at far
SE VA/NE NC beaches).
3. Dry weather conditions under mostly clear skies.
For Sunday...dry and sunny conditions will continue as west winds
start to slacken. Gusts should average 25-30 mph at the immediate
coast. High temperatures slowly rebound into the mid 60s as
westerly/zonal flow develops aloft. Sfc winds become more
southwest Sunday night, which will contribute to warmer overnight
lows ahead of an Alberta Clipper type system approaching the
region. Expect lows around 50 degrees.
.LONG TERM /MONDAY THROUGH THURSDAY/...
High pressure settles across the sern states Sat night and Sun as
intense low pressure moves into eastern Canada. Dry with slowly
diminishing winds Sat nite. Lows in the low to mid 40s except upr
40s to lwr 50s sern coastal areas. Highs Sun in the mid 60s. Lows in
the upr 40s to lwr 50s.
Next cold front crosses the region Monday. No significant moisture
noted so expect a dry fropa. CAA lags so expect a milder day with
highs in the upr 60s to lwr 70s. Lows in the 40s except lwr 50s sern
Canadian high pressure builds across the area for the mid week
period. Remaining cool and dry. Highs Tue 60-65. Lows in the 40s to
lwr 50s sern coastal areas. Highs Wed in the 60s. Lows in the mid
40s to lwr 50s.
Low pressure progged to move from the nations mid section Wed to the
Gt Lakes region Thurs. Limited moisture returns in advance of the
approaching warm front. Added slight chc pops Thu across the
northern half of fa with this feature. Highs 65-70.
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
A cold front is approaching from the west this afternoon and is
located over the VA piedmont as of 18z. A broken line of shra has
developed ahead of the boundary, and could clip RIC through 19z.
Otherwise, the front will push across the region this afternoon
into early evening. Shra are expected to increase in coverage
behind the front as additional energy arrives from the sw later
this afternoon and evening. The onset of -shra will likely occur
after 22z for SBY/PHF/ORF/ECG. Overall, pcpn is not expected to
produce much of a vsby restriction, with the exception of only
very brief restrictions in the leading line of shra. Cigs are
expected to drop to mvfr in the wake of the boundary and could
briefly drop to ifr at SBY later this evening. Drier air gradually
arrives from the west later tonight through midday Saturday with
cigs lifting from w-e then scattering through 18z Saturday. A nw
wind will increase to 15-20kt late tonight into Saturday, with
gusts up to 25-30kt, and locally up to 35kt at SBY. High pressure
builds across the Southeast Saturday night into Sunday. A (dry)
cold front sweeps across the area Monday, with high pressure
returning Tuesday and Wednesday.
Generally benign conditions early this morning with winds of 10 KT
or less and seas 2-3 ft/ waves 1-2 ft or less. Significant changes
are coming later today and tonight however, and all zones remain
either in Gale or SCA headlines. As noted by last shift, the real
CAA surge is not expected to arrive until later tonight into Sat
morning. Given rather sharp pressure rises behind the front,
925-950 MB winds between 35-40 kt, falling H85 temps and water
temps arnd 70 F, confidence remains high that enough mixing occurs
to support Gales for the Bay and coastal waters, with strong SCA`s
and frequent gusts a little over 30 KT for the Rivers and
Currituck Sound. Strongest gusts up to 40 KTS looks to be across
the northern waters with gusts to 35 KT across the south. Probably
a secondary surge/increase in mixing Sat evening and with this in
mind have extended the Gale Warning for the coastal waters N of
Parramore Island until 10 pm Sat. As the event unfolds, may need
to extend portions of the Bay into Sat aftn as well but in general
the strongest winds look to occur from midnight-noon Sat so left
them as is for now.
The offshore NW flow will keep seas from building to much higher
than 5-7 ft most areas (highest out 20 NM offshore). Bay waves
build to 4-5 ft. Winds remain elevated on Sunday but should
diminish to some extent and avg 15-20 KT. The next front crosses
the area Mon. Appears another surge (albeit much weaker) will
likely require SCA headlines late Monday or Monday night.
MARINE...Small Craft Advisory from 6 PM this evening to 4 AM EDT Sunday
Gale Warning from 8 PM this evening to 4 PM EDT Saturday for
Gale Warning from 8 PM this evening to 2 AM EDT Sunday for