Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
805 PM EDT sun Mar 9 2014
high pressure will settle over the Gulf Coast states Monday and
Tuesday. Low pressure and its associated cold front will pass
through later Wednesday into Thursday. High pressure will return
for late in the week.
Near term /through Monday/...
surface high over the middle-Atlantic shifts to the south tonight.
Northwest flow aloft has already sent some high clouds into the
County Warning Area. This flow aloft will be the pathway for multiple
shortwaves/vorticity maxes to pass through...mainly with waves of
clouds...through Monday. Thus...expect mostly cloudy skies to
prevail much of the time although there may be some sun returning
later in the afternoon on Monday.
GFS and European model (ecmwf) continue to suggest light quantitative precipitation forecast between 12z-18z across
northern Maryland Monday...no doubt in association with one of the
shortwaves. Continue to favor a dry forecast with relatively dry
low level air in place although a few sprinkles can/T be ruled
Tonight will be chilly but we expect rebounding temperatures
during the daytime Monday with low level flow turning to the
southwest. If clouds break up sooner Monday...then temperatures
could turn out a little warmer than what we are forecasting.
Short term /Monday night through Wednesday/...
a weak cold front north of the region is expected to either approach
or drop into the middle-Atlantic Monday night into Tuesday. There is
some disagreement among models how far south the front will be...and
whether it potentially drifts back north into PA Tuesday. This will
have implications for the exact track of the midweek low
pressure...but in terms of sensible weather Monday night and Tuesday
impacts are expected to be relatively minimal except for cloud cover
and wind direction. These will have implications for
temperatures...due to radational cooling potential Monday night and
downslope potential Tuesday. As of now...expecting low temperatures Monday
night to range from the middle 30s over higher elevations to the middle
40s over metropolitan Baltimore/Washington. High temperatures Tuesday likely will
be a few degrees warmer than Monday...ranging from the upper 50s
near the Mason-Dixon line and the Potomac Highlands to around 70 in
the Charlottesville-Fredericksburg corridor.
On Tuesday night...500mb trough sharpens over the Mississippi
Valley...causing surface low to strengthen as it moves through the
Ohio Valley. Overall model trend slows the system down by several
hours...so scaled back precipitation chances to areas west of the Blue
Ridge. Low temperatures mostly in the upper 30s to low 40s...so any precipitation
Tuesday night would be liquid.
The low continues to strengthen Tuesday as it moves through the
middle-Atlantic and the 500mb trough digs through the Ohio Valley.
There are model differences regarding the exact track of the low and
how fast it crosses the region...which will affect the amount of
rainfall for the forecast area. General consensus among models is
that heaviest precipitation will be north of the surface low...so a more
northerly track would keep most rainfall north of the Mason-Dixon
line...while a more southerly track would mean enhanced rainfall in
our forecast area. Favored the cooler guidance for temperatures
Wednesday due to expected cloud cover and rain...with 40s/50s along
and west of the Blue Ridge and 50s/60s east.
Long term /Wednesday night through Sunday/...
low pressure will be over Cape Cod by late Wednesday night and precipitation
will taper off locally through the early morning hours on Thursday.
There is a slight chance for light snow for most of the area if any
precipitation hangs around long enough for the cold air to fill in behind
the low on Thursday morning. Otherwise...dry and chilly northerly
flow will fill in for the day on Thursday bringing mostly sunny
skies and well below normal temperatures. Expect temperatures to
only get into the upper 30s for most of the area...about 15 degrees
The cold blast Thursday will be short lived however...with
temperatures returning to the middle to upper 50s Friday as high
pressure over the southeastern US stretches up into our area.
Southwest flow will fill in as the high moves off the Carolina coast
Saturday morning and high temperatures on Saturday afternoon should reach
into the low to middle 60s. Mostly to partly sunny skies should make
for a very pleasant start to the weekend. Nighttime lows Friday and
Saturday will be in the middle to upper 30s.
Low pressure located north of the Great Lakes will cause a weak cold
front to swing through the middle Atlantic Saturday night. Aside from some
light precipitation over the Potomac Highlands...local impacts should be
limited to increased cloud cover Saturday evening and a high
temperature on Sunday in the 50s...about 10 degrees cooler than the
high on Saturday.
Aviation /23z Sunday through Friday/...
VFR conditions are expected tonight and Monday...with high clouds
lowering into a middle deck around 10k feet. Northwest winds will become
variable overnight. SW winds will increase Monday morning with
generally 10 to 15 knots through afternoon.
Monday night...VFR. SW winds around 5kt...becoming west-northwest by morning.
Tuesday...VFR. West-northwest winds 5-8kt.
Tuesday night...primarily VFR. Possible fog late. Winds S 5kt.
Wednesday...sub-VFR likely with rain. Winds S winds 10kt...possibly
becoming west-northwest late. Gusty northwest winds expected Wednesday night into Thursday.
northwest winds have diminished early this evening...and Small Craft Advisory was allowed
to expire. Winds become variable tonight but as high pressure
settles south a south/southwest wind will develop for Monday. Due
to cold water temperatures not expecting Small Craft Advisory gusts to mix down at the
moment and therefore no advisory at this time.
Sub-Small Craft Advisory conditions likely Monday night through Tuesday night. Small Craft Advisory
likely Wednesday as winds increase ahead of approaching low
pressure...possibly even gales.
A Small Craft Advisory may be necessary through the day Thursday as
low pressure moves away from the eastern Seaboard and again
overnight Friday in breezy southeasterly flow.
District of Columbia...none.