Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
352 am EST Sat Dec 20 2014
high pressure will persist through Sunday. Low pressure will
track up the middle-Atlantic coast late Monday. A strong cold front
will then pass through the area late Wednesday.
Near term /through tonight/...
the middle Atlantic is between two shortwave troughs this morning...one
across New York and another approaching from the Ohio Valley. High
pressure is centered overhead and has led to calm and dry conditions
Moisture advection from SW flow aloft will continue ahead of the
approaching shortwave trough and cirrus will continue to move into
the region from SW to NE this morning. Precipitation across the southeast
US will continue to move north-northeast this morning. There is a
slight chance of snow to skim the central foothills before noon
today as moisture moves northward. It is not likely as SW flow aloft
is expected to become westerly midday limiting moisture advection
into the mid-Atlantic. Most if not all precipitation should stay south
of the outlook area. Clouds and low sun angle will limit heating
today and temperatures will only climb into the upper 30s to around 40
Multiple rounds of energy will pass over the middle-Atlantic through
tonight. Due to little forcing as the jet stream is further
south...dry conditions are expected through tonight. Subsidence
behind any vorticity maxes may lead to some clearing. Forecast min temperatures
should be in the upper 20s to low 30s in urban areas. Clearing may
result in temperatures dropping a few more degrees.
Short term /Sunday through Monday/...
high pressure extends from New England down into the middle-Atlantic
Sunday. Models suggest a good deal of sunshine with maxima near
High pressure edges a little east Sunday night into Monday...with
pressure pattern signaling some semblance of a wedge. At the same
time...southern stream shortwave energy is also forecast to move
northeast on Monday.
Result will be increasing/thickening clouds Sunday night but think
any precipitation will remain to the south through daybreak. Trend of the
models is to delay precipitation a little longer during the day Monday.
Leaned toward European model (ecmwf)/srefs for timing. But if precipitation arrives early
enough...Monday morning may see a wintry mix of precipitation particularly
Blue Ridge westward. Bulk of the precipitation Monday afternoon/evening
appears to be rain but a wintry mix including potential icing from
freezing rain may linger across the higher elevations of the Potomac
Highlands into Monday evening.
Long term /Monday night through Friday/...
shortwave exits late Monday night...but The Wedge remains into
Tuesday and with low level moisture in place chance of rain or
Attention then turns to a deep/strong upper level trough sending
a cold front through late Wednesday. Decent low level jet and
plume of moisture are expected to be transported ahead of the
front on Wednesday...leading to showers. Maxima are expected to
be warm for this time of year and have trended maxima near 60 east
of the Blue Ridge for Wednesday.
Dynamic system moves away Wednesday night. Tight gradient and cold
advection bring a windy and cooler Christmas day...although maxima
may actually still be a few degrees above climatology.
Aviation /09z Saturday through Wednesday/...
VFR conditions expected today and tonight. Clouds will increase from
SW to NE across the terminals today. Middle-high level ceilings expected.
-Sn is possible but not likely at cho this morning. Northwest winds
around 5 kts expected today and tonight.
Developing wedge and area of low pressure will likely bring some
rain and at least MVFR conditions Monday. If precipitation arrives early
enough Monday morning...it may begin as a mix.
IFR or lower conditions are then expected Monday night into Tuesday
with wedge in place and areas of rain or drizzle. Strong cold front
follows late Wednesday with showers/possibly gusty winds.
high pressure will persist across the waters today and tonight. Northwest
winds 5-10kts are expected on the waters today and weaken further
High pressure over New England on Sunday moves offshore early in the
week. Small Craft Advisory conditions are possible in southerly flow ahead of a cold
front on Wednesday...then behind the front for Wednesday night and
District of Columbia...none.