Scientific Forecaster Discussion
fxus61 kakq 240917
Area forecast discussion
National Weather Service Wakefield Virginia
517 am EDT Mon Jul 24 2017
a weakening cold front will gradually push across the area on
Monday and stall across the Carolinas through the middle of the
upcoming week. Temperatures will cool down to near normal levels
Near term /through tonight/...
current analysis reveals weak sfc low pressure pushing along a
wavy frontal boundary over the Delmarva just north of the local
area. Aloft, broad upper level trough continues to dig east-southeast
across the Ohio/TN river valleys, with west-northwest flow aloft.
Coverage of showers/tstms has gradually diminished this morning.
Weak front will gradually be forced south into the local area
today. Pre-frontal southerly flow will bring one more warm and
moderately humid day across the local area. However, lingering
clouds should keep southern tier of the area at least a category
cooler. Cams not nearly as generous with convective potential
today, largely a result of drier air nudging in from the northwest.
Thus, have gone no higher than a 20% pop for most of Richmond
Metro area up to the lower Eastern Shore of Maryland. Farther south,
better deep layer moisture and lift, as well as a more tangible
convective trigger (upper height falls) warrant a chance pop
30-50% across southeast Virginia/NE NC zones. However, slightly cooler
temperatures mean convective temperatures will likely be met
later in the day. Have therefore delayed onset of pop until
after 18z. Expect most locations over the northern and central
County Warning Area remain dry today. Highs in the low to mid 90s (where
clearing occurs earliest), upper 80s to near 90 southeast. This will
result in heat indices around 100 degrees across south central
Virginia into the Tidewater and NE NC this afternoon, and in the 90s
to around 100 in Metro Richmond (slightly lower TD values), and
therefore should preclude the need for additional heat
Surface front slowly drops across the area tonight, before
stalling along/south of the Virginia/NC border by morning. Showers
quickly wane with minimal shear and waning instability. Slightly
cooler and a bit more comfortable with early morning lows in
the upper 60s to low 70s in the Piedmont...low to mid 70s
Short term /Tuesday through Wednesday/...
front stalls across east NC Tue, with mainly diurnal tstms
possible again over the S (20-35%), and 10-15% north (mainly south
of US-460. Seasonable highs upper 80s to lower 90s. Wednesday
still looks to be the nicest day we've seen in awhile
temperature-wise, with markedly drier TD values by Wed into Thu.
Sfc high pressure traverses New England with Max temps only
reaching the the mid/upr 80s with discernibly lower humidity
levels. Stalled frontal boundary to our south will still keep a
chance of mainly aft/eve showers/tstms in the forecast over our
southern forecast area (pops 20-40%, again mainly central and southern
Long term /Wednesday night through Sunday/...
the mid-Atlantic region will generally be situated between a
trough off the Carolina coast and trough digging through the
Great Lakes and Ohio Valley Wednesday night and Thursday. The
Great Lakes/Ohio Valley trough gradually drops into the region
Thursday night and Friday as an associated cold front approaches
from the northwest. Pops are mainly aob 20% Wednesday night/Thursday
and then increase to 30-40% chc for showers/tstms Friday ahead
of the approaching front. Highs Thursday/Friday are mainly in
the upper 80s to around 90, with mid 80s at the immediate coast,
and overnight lows in the low/mid 70s. The trough is progged to
settle over the region by Saturday/Sunday with the cold front
pushing through Friday night into Saturday, before stalling off
the Carolina coast. Forecast pops for showers/tstms are ~40%
Friday night, and then generally 20-30% northwest to 30-40% southeast next
weekend. High temperatures trend down into the mid 80s as the
trough settles overhead with lows in the upper 60s to low 70s.
Aviation /09z Monday through Friday/...
conditions have recovered to VFR at most sites early this
morning, with heavier showers and convection waning and shifting
north-northeast of the area terminals. Some patchy fog is possible across
the Piedmont during the overnight but am not expecting any
significant impact to taf sites at this time.
Isolated to widely sct thunderstorms and rain possible this afternoon, mainly at
orf/ecg. Confidence in areal coverage remains low and have held
out mention attm. Any convection quickly wanes tonight, with VFR
conditions expected overnight into Tuesday.
Outlook: convective continues for south central Virginia and NC for
Tuesday. VFR should dominate through this period, with periods
of sub-VFR possible in heavier showers/tsra. A weak cold front
pushes into the area for the mid week period.
west-SW gusting between 20-25kt over ches Bay expected to diminish
around sunrise as an area of weak low pressure tracks east-northeast of
the Delmarva. Otherwise, a sfc thermal trough remains over
cntrl Virginia today as a cold front drops down from the north-northwest. The
front is expected to slowly cross the waters late tonight into
Tue morning. Isolated to scattered aftn/evening thunderstorms
will be possible once again with locally strong wind gusts,
heavy rainfall, and frequent lightning being the main impacts.
Winds generally SW aob 15kt today/tonight. Decided to put up
Small Craft Advisory for the Chesapeake Bay, Currituck Sound
and for the lower James River. Winds have picked up over the
waters due to increasing pressure gradient. Expect this to be a
short term event until around 4 am. Seas will be 2 feet
nearshore and up to 4 feet 20 nm. Showers and thunderstorms will
affect the Lower Bay and Atlantic coastal waters til around
midnight. Winds will remain mostly SW on Monday but expected to
be below Small Craft Advisory criteria.
A frontal boundary crosses the area early Tuesday bringing a
windshift to the E-NE. Winds are expected to generally remain around
15 knots behind the frontal boundary. Seas will range from 2 to 4
feet with some areas to around 5 feet at 20 nm in the far northern
zones. The extended marine period will be dominated by mainly weak
onshore flow as a frontal boundary stalls across the region.
Afternoon showers and thunderstorms will remain possible through the
forecast period.Ight with seas averaging 2-4ft north/2-3ft
south and waves 1-2ft during this time.
The cold front gradually stalls out just south of the area by
late Tue night/Wednesday morning with high pressure building
north of the region. This will limit aftn/evening thunderstorms
to srn waters invof the weak trough and/or seabreeze boundaries.
Conditions generally dry on Thu. Then low pressure and an upper
level shortwave are expected to swing through the region Thu
night/Fri...bringing the next best chance for rain to the waters.
Wind speeds aob 15kt the rest of the week. Wind direction veers
to the north on Tue (behind the cold front)...onshore/NE-E Tue
night through Wed...E-SW Wed night into Thu...then S-SW Thu
night/Fri. Seas average 2-4ft; waves 1-2ft.
did not set any records over the past few days (even with the
101 degree temperature reached at ric on sat).
* Date: sun(7/23)
* ric: 103/1952 (actual 97)
* orf: 103/2011 (94)
* sby: 103/2011 (88)
* ecg: 104/1952 (91)