Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
243 am EST Friday Nov 27 2015
high pressure will control the weather pattern through tonight. A
cold front will pass through the area late Saturday into Sunday
before stalling off to our south early next week. A stronger cold
front will pass through during the middle portion of next week.
Near term /through tonight/...
generally quiet weather early this morning...with fog possible closer to
daybreak. Cloud cover has been off/on all night...with hints of
fog development in The Breaks. Thinking the best timing would be
08-13z...with any fog dissipating there aftr.
For today...high pressure dominating at the surface over the middle-
Atlantic...with a broad ridge aloft. Weak southerly flow incrsg moisture
levels today...but with westerly flow in the middle/upper levels...the drier air
aloft will aide in keeping things mostly sunny today...with only
high level clouds moving in for the evening. For temperatures...sided with the
warmer mav/European model (ecmwf) solution as guidance all week has been on the lower
side when concerned with high temperatures.
The surface high becomes suppressed to the south tonight as low pressure
trekking north of New England drags its associated cold front closer
to the mid-Atlantic. The overall passage of the cold front from the
00z model guidance looks to be slow...with weakening as it pushes
south...as the ridge transitions into a more zonal flow aloft.
Maintained a mainly dry night...with only a chance of -shra by the
second half of the night in just far western portions of the County Warning Area.
Under increased cloud cover...and still southerly flow...low temperatures in the
Short term /Saturday through Sunday/...
cold front just north of the Mason-Dixon by 12z Sat...with light
rain showers forming out ahead of the front. Some question on the
eastern extent of the precipitation...with the model solutions ranging from
the PA/Maryland border to south into central Virginia. Have sided with a
conservative solution for the time being as a lack of forcing
outside the front looks to minimize precipitation potential. As such...will
keep the precipitation right close to the frontal boundary as it slowly
sinks south during the day...eventually dipping south of the PA/Maryland
border by 00z sun. The front slowly continues to sink south Sat
night into Sun morning...reaching southern Virginia late in the day
before stalling. Scattered showers possible along the front during Sat night
Temperatures ahead of the front on Sat will still reach the middle 50s to middle
60s...going yet again with a mav/European model (ecmwf) blend...which has been
trending well. Guidance in temperatures ranging greatly...and with
uncertainty where the frontal boundary sets up...could see the
potential of temperatures mainly closer to the Mason-Dixon on the cooler
side. By sun...cold air advection behind the front will keep highs in the
Long term /Sunday night through Thursday/...
a cold front will stall out to our south Sunday night and remain
nearby through Monday. A north to northeast flow will allow for
chilly conditions during this time. Warm and moist air will
overrun the surface cooler air in place...resulting in plenty of
clouds and even the chance for rain. The best chance for rain will
be across central Virginia into the Potomac Highlands where
overrunning will be deepest. Farther to the northeast...drier air
may work its way into the area from New England and this may keep
much of the time dry. Certainty in the forecast remains low due to
the tight gradient between dry conditions and a soaking rain being
Low pressure will strengthen as it moves through the plains into
the Great Lakes Monday night and Tuesday. The boundary to our
south will begin to retreat to the north as a warm front...and
overrunning will increase across the entire area during this time.
Plenty of clouds are expected along with the likelihood of rain.
The cold front will pass through the area Tuesday night into
Wednesday and more showers are likely during this time. Drier air
should move in behind the cold front later Wednesday and Thursday
as high pressure builds in from the Ohio Valley.
Aviation /08z Friday through Tuesday/...
outside of early morning fog potential...VFR conditions for the
taf period. Fog has been slow to form this morning...but thinking
best chance still between 08-13z...with visible dropping 3-5sm.
Confidence just isnt there at this time with IFR visible. Light/vrb winds
will increase slightly aftr 14z from the south...though still less
than 10 kts.
Increasing middle-high level clouds tonight into Sat with precipitation approaching
from the north and west. Kmrb may see a shower late tonight/Sat
morning...with the better chance for the remaining taf sites late Sat
into Sun morning. Possible sub-VFR conditions with this precipitation...especially Sat
night with IFR ceilings possible. Once the precipitation tapers off sun...expecting
conditions to improve to VFR. Winds light/vrb over the weekend.
A cold front will stall to the south Sunday night through Monday.
A north to northeast flow is expected. There should be enough dry
air for VFR conditions across the northeastern terminals...but
MVFR ceilings and rain are possible farther south and
west...especially across kcho. The boundary will return north as a
warm front Monday night and Tuesday. Rain is likely along with
subvfr ceilings/visibilities across all of the terminals. IFR conditions are
possible during this time.
sub-Small Craft Advisory conditions through the weekend. A cold front will stall
south of the waters Sunday night through Monday before returning
north as a warm front Monday night and Tuesday. The pressure
gradient may be strong enough for wind gusts to approach 20 knots
across middle portions of the Bay and lower tidal Potomac River
Sunday night into Monday. Otherwise...sub-sca conditions are
Another cold front will pass through the waters Wednesday.
Thanksgiving day was the warmest Thanksgiving since 2007...when
highs were in the 70s. In addition...the 63 degree high at iad
tied for the 7th warmest Thanksgiving on record. However...the
period of record at iad is shorter than at dca/BWI...where
Thanksgiving 2015 did not even rank in the top 10.
District of Columbia...none.