Scientific Forecaster Discussion
fxus61 kakq 251823
Area forecast discussion
National Weather Service Wakefield Virginia
223 PM EDT Sat Mar 25 2017
high pressure remains offshore the southeast coast through
Monday. A weak frontal boundary drops south to the Delmarva
Sunday morning before lifting back to north Sunday night and
Monday. A cold front crosses the region Tuesday night.
Near term /until 6 PM this evening/...
late morning analysis indicates surface high pressure centered
well off the southeast Continental U.S. Coast, with west-southwest flow aloft. Warm
conditions prevail with temperatures averaging from the mid 60s
to around 70 f as of 15z/11 am. Skies are free of low-mid clouds
but a fair amount of high clouds are streaming across the area
so will keep sky cover in grids of 30-50% today leading to
partly sunny wording for most areas. SW winds will avg 10-15 mph
with gusts to 20-25 mph but still may see the winds on the
Eastern Shore weaken enough to allow the direction to back to
the S or south-southeast along the coast this aftn (which will allow
readings to be steady or even fall a few degrees there).
Dewpoints noticeably higher today than on Fri...mainly will
average from the u40s- l50s. Highs this aftn to avg in the upper
70s to around 80 f west of the Bay to the lower-mid 70s closer
to the coast (and locally in the 60s immediate coast of the
Short term /6 PM this evening through Monday/...
remaining dry/mild tonight ahead of low pres lifting east-northeast from
the mid MS valley into the wrn Ohio Valley. A weak sfc boundary
will settle over the ern shore by late tonight resulting in
light onshore winds and possible broken St. Otherwise...S winds
will prevail under mainly broken-overcast cirrus. Lows M-u40s on the ern
shore to the l-m50s elsewhere.
Weakening low pres (sfc-aloft) will continue to track NE the
Great Lakes sun-Sun night...pushing a weak low level boundary
into/across the forecast area. Only slight forcing aloft W/ this
system...which will likely limit pcpn coverage. Otherwise...vrb
clouds and mild W/ pops mainly confined to I 95 on west (20-30%) by
late Sun afternoon/Sun night. Highs sun from the l-m60s along
the coast/on the ern shore to the l-m70s inland (in Virginia/NE nc).
Lows Sun night in the u40s- around 50f on the ern shore to the
Initial system lifts into/through New England Mon...leaving forecast area
W/ continued mild/warm conditions as hi pres (sfc-aloft) remains
invof southeast Continental U.S. Coast. Vrb clouds Mon W/ pops mainly aob 20%.
Highs mainly in the 60s on the ern shore to the l-m70s
Long term /Monday night through Friday/...
medium range period will remain mild, courtesy of warm southerly
flow from lingering high pressure just offshore of the mid-Atlantic
coast. Other main weather feature of note will be a rather
progressive mid-level shortwave traversing the western/central Continental U.S.
Late Sat-Monday, before lifting east-NE across the mid-south toward the
local area on Tuesday. High end chance pop remains in place for
showers and sct T-storms. While the system will be weakening, given
decent instability and favorable diurnal timing, will continue
thunder wording for all but far NE zones (later timing). Shortwave
ridging behind the wave will bring slightly cooler, albeit still
mild, and drying wx Wed and Thu. Forecast highs mainly in the 60s to
near 70 far north and along the immediate coast...70s to near 80
west of the Bay on Tuesday, 60s to mid 70s on Wednesday...with temps
trending back to around climo normal for the latter half of next
week. Next chance of rain comes by the end of the period late next
week in association with another weakening southern stream upper low
traversing the southern tier of the country. For now, rain chances
are re-introduced by late on Thu/Fri.
Aviation /19z Saturday through Thursday/...
high pressure centered offshore will allow for VFR conditions
to continue through this afternoon and the first half of the night.
Sub-VFR conditions will be possible late Saturday night and into
Sunday as a boundary pushes south into northern portions of the
area. Southwest winds, 10-15 knots with gusts of 20-25 knots, will
persist through the afternoon and early evening hours before
diminishing around sunset.
MVFR and potentially IFR conditions will be possible early Sunday
morning, mainly after 10z, at ric/sby due to patchy fog/low
ceilings. Conditions should improve by late Sunday morning besides
sby where low ceilings may linger into Sunday afternoon. A few
showers will be possible by the end of the forecast period with only
brief periods of reduced aviation conditions possible during times
Outlook: unsettled weather conditions will persist across the region
through mid-week. Sub-VFR conditions will be possible late overnight
and into the early morning hours primarily due to low ceilings.
Scattered showers and thunderstorms will also be possible late
Sunday night into Monday and once again late Tuesday into Wednesday.
Periods of reduced aviation conditions will be possible during times
high pressure is well offshore with a weak wedge left in the Lee
of the Appalachians. This feature should delay the onset of rain
until mid to late morning as a cold front continues to advance
on the area...effectively outrunning (or getting ahead of) the
precipitation by late morning/early aftn. Weak troughing along
the coast will cause the pressure gradient to tighten invof the
cold front. Meanwhile, weak warm air advection will act to hamper
the development of stronger winds. Overall, winds become S-SW
10-15kt (up to 20kt nrn coastal waters) by early aftn; peaking
during the cold frontal passage. Seas build to 2-4ft; waves to
2ft. Little change to the airmass tonight behind the front as
warmer air stays in place with strengthening high pressure
building well north of the waters through Sun night. North winds
tonight through sun aob 15kt...becoming NE-E and diminishing to
aob 10kt Sun night. Seas average 2-3ft; waves average 1-2ft.
Main high pressure slides over nrn New England/Canadian Maritimes
on Mon. East-se aob 10kt. Weak wedging remains in place in the Lee
of the mts as a very strong low pressure system tracks into the
upper Great Lakes Mon and across Ontario/Quebec Mon night. The
pressure gradient tightens up late Mon night into Tue aftn ahead
of the front and S winds will increase to 15kt Bay and 15-20kt
all coastal waters. Seas generally build to 3-4ft in this
timeframe (up to 5ft possible coastal waters north of Parramore
island). Waves generally 2ft; occasionally up to 3ft. Small Craft Advisory flags
are not anticipated.