Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KAKQ 281505
Area Forecast Discussion
National Weather Service Wakefield VA
1105 AM EDT TUE JUN 28 2016
A cold front approaches from the west today, as a pre-frontal
trough remains over the local area. The front will slowly move
across the region late this afternoon through tonight. Weak high
pressure builds in from the north Wednesday and Thursday as the
front stalls across the Carolinas. The next cold front approaches
the region late in the work week.
.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --Latest surface analysis places the upstream cold front over the Ohio
River with a pre-frontal trough over central Virginia. Aloft, GOES
water vapor imagery and RAOB plots indicate shortwave energy over
West Virginia/western Virginia. Water vapor imagery also depicts a
deep plume of moisture streaming northeastward from the Gulf of
Mexico. Precipitable waters have climbed to over 2 inches across the
region, which is +2 standard deviations. Pre-frontal showers are
expanding in coverage late this morning as the upper wave approaches
from the west. This matches up well with inherited likely POPs, so
no changes made to near term POP forecast other than to increase
the Maryland Eastern Shore to categorical. Locally heavy rainfall
still expected. Rainfall amounts in excess of 2 inches have been
observed over the Maryland Eastern Shore. Temperatures also on
track. Only other change made was to time POP`s late today through
this evening. Confidence is increasing that a line of scattered
showers and thunderstorms will develop ahead of the cold front
over the Piedmont late today, even as dry air begins to work in
from the west. Some clearing is expected with MLCAPE values
progged to increase to 1,000 to 1,500 J/kg over the Piedmont this
afternoon. Deep layer shear remains marginal as strongest height
falls remain north of the region. Gusty winds are possible under
the strongest storms. SPC maintains only a marginal risk for
Current analysis depicts low pressure over eastern Canada, with a
surface cold front extending SW through western NY and into the
Ohio Valley. A pre-frontal sfc trough is in place along/just E of
The Appalachians. Ongoing widespread shower with embedded tstm
activity over the Ches Bay and eastern Shore, with coverage more
isolated to widely scattered across central and south central VA
(with dry conditions over far se VA and ne NC). GFS/NAM reveal
that although CAPE is very limited, elevated instability per
negative showalter indices over much of the area has been
sufficient when combined with decent lift to keep showers going
along with a few tstms. Activity off to the W/SW of metro richmond
likely to increase in coverage over the next few hrs and will
carry likely POPS of 60-70% from the eastern shore back W/SW
through cent ral and south central VA through the morning, tapered
to only low chc POPS over the far SE through mid morning. However,
expect highest coverage of precip to gradually shift E/SE through
the late morning/early aftn hrs, with likely POPS overspreading se
VA and ne NC by late morning through much of the aftn. Meanwhile,
some breaks in the clouds are expected over central VA as POPS
decrease somewhat by mid aftn onward. If enough clearing occurs
this aftn, could see some marginally strong tstms develop, mainly
W of ches Bay and SPC has this approximate area in a marginal risk
for severe tstms. Still, greater effective shear of 30 Kt+ should
stay N of the entire area closer to stronger h5 height falls since
the upper low will be well to our north across Ontario. Given the
continued moist airmass with precipitable waters around 2.00" and
relatively weak steering flow aloft (at least through 18Z) locally
heavy rain will be the main concern and will address in the HWO.
Highs generally in the low-mid 80s today (possibly staying in
upper 70s/around 80 depending on rain coverage through the aftn).
Upper low tracks from NY state to New England later tonight, a
slightly slower secenario compared to past model runs. Still
expect the cold front to push through the local area, though the
front may hang up near the coast. Height falls will result in
cyclogenesis just off the Northeast coast Tuesday night. As the
low wraps up, lingering mid level moisture across the northeast
forecast area in concert with strengthening forcing for ascent is
expected to produce scattered showers Tuesday evening. Best
chances will be from the Northern Neck to the Eastern Shore.
Drying late Tuesday night with a clearing sky inland. Partly-
mostly cloudy near the coast. Lows range from the mid to upper
-- End Changed Discussion --
.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
Broad, upper level trough pushes across the region Wednesday. The
frontal boundary expected to stall in the vicinity of northeast
North Carolina as high pressure builds in from the northwest.
Departing 70+ knot upper jet and enough lingering mid level
moisture (precipitable waters drop below 1.5 inches) should be
enough for widely scattered diurnally driven showers and
thunderstorms, mainly over far southern VA and ne NC. Highs
generally in the mid 80`s under a partly cloudy sky. Best chances
for measurable precipitation will be south of the Albemarle Sound
Wednesday night, but will keep mention of slight chance showers.
Lows generally in the low to mid 60`s N to upper 60s S.
Surface high pressure centers along the Mid-Atlantic coast
Thursday morning as the next upper level shortwave approaches
from the west. Low pressure progged to develop over the Southeast
states with an inverted trough extending northward over the
central Appalachians. Upslope flow and the approaching wave will
result in showers and thunderstorms over the higher terrain. GFS
is wettest model and would support high chc POPS into the CWA
while the NAm/GEM are drier. Expect much of the forecast area to
remain dry, but will mention a 20-30% POP for showers coming off
the higher terrain Thursday afternoon into areas W of the Bay.
Otherwise, near seasonal temps again with highs forecast in the
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Active northern stream upper trough will remain the dominant wx
feature through the medium range period. Resultant W-NW flow will
continue for the late week/Holiday weekend period.
Meanwhile, at the surface, a rather stagnant pattern looks to set up
with weak front/sfc trough dropping into the area and lingering over
the local area. Warm, moist airmass (PW AOA 2" from Friday night
through the weekend) in tandem with the boundary and numerous
disturbances riding across the area in WNW flow aloft will bring a
solid chance for mainly diurnally driven showers and tstms. Have
continued solid chance pops each day during this period.
Stronger front crosses the area by later Sunday into Monday.
For temps, pattern favors temperatures hovering right around climo
normal...with highs in the mid to upper 80s. Early morning lows
generally in the 60s.
.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
Early this morning, a cold front was dropping thru the Ohio
valley. The front will move southeast and pass acrs the Mid Atlc
States tonight into Wed morning. An upper level disturbance and
surface trough will produce sctd showers and tstms today into
this evening, with additional sctd pcpn possible with the front
tonight. Conditions are expected to generally be MVFR with the
weather, but a few hours of IFR will be possible at RIC and SBY.
Winds will be light and generally fm the south.
OUTLOOK...Expect mainly dry/VFR conditions for Wed and Thu, as
high pres nudges in fm the WNW. More chances for pcpn return next
Early this morning, SSW winds were mainly 5 to 15 kt acrs the
waters, and will remain at those speeds today into tngt, as a
pre-frntl trof lingers ovr the area and then the cold front
approaches fm the WNW. The front and accompanying wind shift to
the N-NE drops through the waters Wed morning into Wed aftn with
high pres pushing into the Great Lakes and OH Valley. This will
maintain a NE to E flow later Wed and Thu. Weak front/sfc trough
will meander over/just south of the area for the late week period,
and will serve as the focus for late day convection over the
region late in the week and through the weekend.
Chances to add to an already wet month mainly tonight and Tue. June
has been another wet month at Richmond, the monthly total rainfall
through the 24th stands at 6.92" and already makes this the 9th
wettest June on record (2004 is wettest June with 9.93").