Scientific Forecaster Discussion
fxus61 klwx 151507
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
1007 am EST Fri Nov 15 2019
low pressure will meander off the Carolina coast through the
weekend. Meanwhile, a reinforcing cold front will move
southward out of Pennsylvania today into tonight as high
pressure builds over northern New England. The high will move
slowly eastward into the Canadian Maritimes this weekend while
low pressure drifts northeastward offshore. A second area of low
pressure may develop near the Carolinas and move northeastward
during the first half of next week.
Near term /through tonight/...
the cirrus shield associated with developing low pressure off
the Carolina coast has begun to thin out across much of the
area. Will likely continue to see bands of high, thin cirrus
throughout the day, as the low meanders off the Carolina coast,
very slow to begin moving to the northeast throughout the day.
As a result, and dense cirrus likely remains over southern
Maryland. A few light showers are possible on the periphery of
the approaching low across southern Maryland and the far
southern waters. Other than that, things will stay dry today.
Most guidance has high temperatures eclipsing 50 degrees this
afternoon, and am inclined to believe that given the lack of
clouds over over much of the region at this time. Low to mid 50s
can be expected by the afternoon.
thicker clouds and perhaps the very edge of some light rain may
continue to oscillate into southern Maryland tonight. Much of
the rest of the area will likely see continued scattered to
broken high clouds as a secondary reinforcing cold front drops
south. A sprinkle or flurry can't be ruled out over the
mountains as the front drops south, with the NAM BUFKIT
soundings suggesting perhaps a brief period of freezing drizzle
on the ridge tops this evening (but very low confidence).
Otherwise, mainly dry and cold with increasing northerly winds
Short term /Saturday through Sunday night/...
low pressure will continue to spiral offshore, only slowly
trekking northeastward with high pressure over the Canadian
Maritimes blocking a hastier exit. Periods of clouds and brisk
northeasterly winds will linger much of the weekend with below
normal temperatures, especially on Saturday, in the pressure
gradient between the two systems. Some guidance tries to pull
precipitation westward into the marginally cold air Sunday, but
this is a low probability outcome at the present time.
Long term /Monday through Thursday/...
reasonable consensus exists regarding the larger features
through the long term, with the devil being in the details. At
the start of the period, low pressure will be east of Ocean
City, Maryland, heading slowly northeastward parallel to but
fairly far from the coast. However, an approaching sharp
shortwave will be moving in from the west. This likely attempts
to induce new precipitation development on the back side of the
low on Monday even though the low center itself will likely be
up near Cape Cod by day's end. Temperatures will remain cool
with the clouds and risk of rain, not to mention the gusty
By Tuesday, the low and shortwave are both passing well
northeast of the region, so the risk of rain should be ending.
However, a reinforcing chilly air mass will be over the region,
and with the longwave trough still overhead, can't completely
rule out a stray convective shower or perhaps some upslope
rain/snow showers in the mountains. That all said, the greater
sunshine expected should result in a slightly milder day.
Another shortwave with perhaps a weak surface reflection will
cross the region Wednesday, resulting in another risk of a few
showers. Temperatures won't change much.
The pattern finally changes by Thursday on most guidance as the
trough starts moving out and high pressure builds to the south
with a ridge moving in overhead. This should cut the risk of
rain down to near nothing, allow greater sunshine, and help to
moderate temperatures a bit more, with readings approaching
Aviation /15z Friday through Tuesday/...
VFR expected through the weekend, with small chance of sub-VFR
if any more appreciable precip/low clouds meander northward from
distant low pressure offshore. Light northwest flow today becomes NE
and strong tonight through the weekend with gusts 20-30 kts.
Sub-VFR possible Monday with rain potentially developing over
the region while low pressure moves northward up the coast.
winds turn north to NE tonight into the weekend behind a reinforcing
cold front. Tight gradient between low pressure offshore and
high pressure will bring Small Craft Advisory conditions to all
waters by this evening, as a result a Small Craft Advisory
begins this evening. Winds become stronger in the central Bay
and lower tidal Potomac, likely reaching gale conditions, so a
Gale Warning begins at midnight, continuing through Saturday
morning. Small Craft Advisory conditions likely continue through
Gusty winds to at least Small Craft Advisory levels may even persist Monday, but
likely wane by Tuesday as coastal low pressure finally departs
to the northeast.
District of Columbia...none.
Marine...Small Craft Advisory from 6 PM this evening to 6 PM EST
Saturday for anz530>532-535-536-538>542.
Small Craft Advisory from 6 PM this evening to midnight EST
tonight for anz533-534-537-543.
Gale Warning from midnight tonight to 6 PM EST Saturday for
Small Craft Advisory from 10 am to 6 PM EST Saturday for
Gale Warning from midnight tonight to 10 am EST Saturday for