Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Baltimore Maryland/Washington District of Columbia
612 am EDT Friday Oct 24 2014
high pressure will build overhead through Saturday. A reinforcing
cold front will pass through the region late Saturday night into
Sunday before high pressure returns for Monday. The high will move
off the coast during the middle portion of next week.
Near term /through tonight/...
update...started the Small Craft Advisory for all the waters now -
that was to go into effect at 9am. Gusts beginning to become more
widespread across the area west/ little...if any dissipation through the
an upper level vorticity maximum ribbon helping mix-down the gusty winds at this time
and will continue hovering over the area into the Post-dawn hours this
morning. Occasional gusts in the 20-25kt range...W/ overall surface winds
at a steady 10-15kt clip out of the northwest. The exiting and slow-moving
upper level system from a couple of days ago still hanging around
New England...east of the Hudson River/eastern New York. The vorticity maximum merely
swinging around the backside of the upper low...being pulled along
by the system...not expected to make much eastward progress in the coming
hours. For this reason...winds will stay fairly breezy overnight which
is not all that common - then pick back up even further after dawn.
Trapped low level moisture also mixing-down west/ some of the
gusts...which is keeping dewpoints relatively higher than west/ a northwest
flow regime. Even though skies are generally clear at this time...dewpoints
are remaining relatively high and this is keeping temperatures on the
warmer side. If not for the moisture...temperatures would likely be
dropping well into the 40s and 30s in sheltered valleys...but most
sites are barely at or below 55f currently.
Not quite as gusty today as on Thursday but temperatures will end up in about
around the same levels - m60s...u60s over the southern tier counties.
Plenty of sun today...a few passing upper decks as a precipitation-less
shortwave digs well to our south...over the southern Appalachians. This feature
will keep its influences away from the middle-Atlantic but will help to
usher-in the more calming effect of an upper Midwest high. After the
surface flow dissipates Post-sunset tonight...dewpoints will slowly
rebound again into the 40s...for another relatively mild temperature range for our
overnight lows. Applied a bias-corrected met/mex for today's
high/low temperature grids. Also modified winds in the near/short terms west/
newer hi-res wrk guidance.
Short term /Saturday through Sunday night/...
the nose of a potent upper level jet will make a quick entrance on
Sat...slamming up against the exiting upper level jet from the
offshore low. This fast upper northwest flow will start to bring in the
cloud cover to the mountains on Sat...but leave the remainder of the area
fairly dry and clear until later in the evening. Being on the right-exit
downward motion side of the upper jet will keep the area dry heading
into the weekend. Weak but steady downsloping flow may help bring
temperatures up a few more degree...peaking in the M-u60s - possibly just
above 70f for Sat afternoon.
Low pressure will track through eastern Canada Saturday night and
eventually toward Nova Scotia on Sunday. The cold front associated
with this system will pass through our region late Saturday night
into Sunday. Little forcing and little moisture will be associated
with the front. Therefore...most areas will remain dry with just
a few clouds near the boundary. There may be a few showers along
and west of the Allegheny Front due to an upslope flow...but even
across these areas any precipitation will be light. Leaned toward
the warmer guidance Saturday night due to some cloud cover and a
gradient wind holding off any radiational cooling. Min temperatures are
forecast to range from near 40 along the ridge tops of the Potomac
Highlands to the lower and middle 50s in downtown Washington and
High pressure will approach the region Sunday behind the cold
front...but the gradient will remain strong between the approaching
high and the departing cold front...resulting in breezy conditions.
Northwest winds will gust around 20 to 30 miles per hour during the late
morning and afternoon hours. Sunshine and a downsloping flow will
offset any weak cold air advection...allowing for maximum temperatures to be
above climatology. Of course...the mild conditions may be offset by the
gusty winds. Leaned toward the warmer side of guidance...with maximum
temperatures forecast to range from the 50s in the mountains to the middle
70s across central Virginia into southern Maryland. High pressure
will build overhead Sunday night...causing winds to diminish.
Light winds...mainly clear skies and dry conditions will provide a
good setup for radiational cooling. Therefore...min temperatures Sunday
night will be chilly...ranging from the middle 30s across northern
Maryland and for locations near and west of the Blue Ridge
mountains...to the middle 40s in downtown Washington and Baltimore.
Frost is possible across many locations overnight Sunday.
Long term /Monday through Thursday/...
high pressure will move off the coast Monday and Tuesday. A
southerly wind will allow for milder conditions during this time.
A cold front will pass through the area Tuesday night into
Wednesday...and it will stall out nearby for later Wednesday and
Thursday. Unsettled conditions are possible during this time...but
certainty remains low this far out in the forecast period.
Aviation /10z Friday through Tuesday/...
another breezy afternoon today but a tier lower in terms of peak
gusts...where 15-20kt will be fairly common from after sunrise.
Several more heading into the daytime hours...of the steady breeze
today. Winds will then quickly drop off toward sunset. High pressure
continue strengthening over the area into Sat.
Northwest winds will gust around 20 to 25 knots Sunday. Winds will
diminish around sunset Sunday evening...and light winds are
expected overnight as high pressure builds overhead. South-
southwest winds are expected Monday and Tuesday as high pressure
moves off the coast. VFR conditions are expected Sunday through
a weak upper low will meander just off the coast into the late
night hours tonight...keeping breezy conditions over the area until
later this evening. Small Craft Advisory continued for all the waters today.
A reinforcing cold front will pass through the waters late
Saturday night into Sunday. A Small Craft Advisory may be needed
for portions of the waters Saturday night. A Small Craft Advisory
will likely be needed for northwest winds behind the front Sunday
into Sunday night.
High pressure will build overhead late Sunday night into Monday
before moving off the coast later Monday through the middle
portion of next week. A southerly flow will increase during this
time. A Small Craft Advisory may be needed for portions of the
waters Tuesday and Wednesday.
District of Columbia...none.
Marine...Small Craft Advisory until 6 PM EDT this evening for