Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
348 am EST Friday Dec 19 2014
high pressure builds into the area from the northwest today into
tonight. Weak low pressure will track from the Gulf of Mexico
eastward and off the southeast coast late tonight through Saturday
night. High pressure will be over the area again during Sunday.
Another low pressure area moves northeast out of the Gulf of
Mexico and up along the coast late Sunday night through Monday
Near term /through tonight/...
latest surface analysis depicts ~993 mb low pressure over the Canadian
Maritimes with broad ~1027 mb hi pressure centered over the Midwest
states. The hi will spread east into the middle Atlantic today allowing
for dry conds to continue. Expect a prtly/mostly sunny sky with
temperatures only climbing into the middle to upper 40s with weak cold air advection over the
Dry weather continues tonight with a middle-level short wave trough approaching the
area. The middle Atlantic remains influenced by surface hi pressure centered
over the Ohio Valley. Expect light northwest winds...a prtly cloudy
sky...and low temperatures mainly in the upper 20s to lower 30s.
Short term /Saturday through Sunday/...
weekend forecast continues to trend drier. Surface low pressure slides east
from the gom Sat...with just a weak surface reflection of the low showing
off the southeast CST Sat night. 00z guidance keeps the northern advancement of
precipitation Sat near the NC/Virginia border on average. Have capped probability of precipitation at
20-30%...and only S of I-64. Could be some snow/pl mixed in over the
southern Piedmont but primarily expecting rain. Any precipitation ends everywhere
by late Sat afternoon. Dry conds then for Sat night and sun as hi pressure
centered over the NE states stretches down into the middle Atlantic.
Temperatures over the weekend will be below normal...with highs mainly in
Long term /Sunday night through Thursday/...
forecast updated to raise probability of precipitation through the period (e.G. 60% Monday and
Tuesday night/wed) as confidence for precipitation as increased.
low pressure is expected to develop off off the southeast coast and
track NE off the middle Atlantic coast Monday into Monday night. Timing
differences continue amongst 18/12z numerical guidance...and given
this probability of precipitation will remain capped in the chance category. Probability of precipitation increase to
20-30% Sunday night...with 40-50% probability of precipitation across the area Monday and
Monday night. Precipitation type should generally be rain...although there
could be a brief period of sleet at the onset over the northwest Piedmont
late Sunday night and early Monday morning. Highs Monday should
range from the low 40s northwest...to middle 50s southeast...after morning lows in
the low 30s northwest...to around 40 southeast. Middle-level ridging briefly builds
into the region Tuesday (bringing milder conditions with highs in
the low 50s northwest to near 60 se)...before low pressure and a strong
cold front impact the region Tuesday night into Wednesday. Spatial
and timing differences continue with the 18/12z GFS tracking the
surface low west of the mountains...and the 18/12z European model (ecmwf) tracking the
surface low up the coastal plain. This will have impact on
temperatures and whether the rain is more stratiform or showery. If
the farther west 18/12z GFS were to verify there could be a potential
for thunder. However...even with this solution...surface dewpoints
at or above 60f remain offshore. Dry and breezy conditions will likely
prevail by Christmas day.
Aviation /08z Friday through Tuesday/...
broken middle level cloud deck between 9-12k feet will continue to move east across
through the ovrnight hours as trough of low prs moves east. These clouds
prognosticated to thin out aftr 12z as high prs builds into the area from
the west. North winds a0b 10 kts.
Outlook...low pressure tracks well to our south Sat/Sat night. This
may bring a period of broken/overcast conditions but ceilings are expected to
remain 4-5 k feet or higher. High pressure builds to the north of
the area Sunday. A series of low pressure systems and complex
frontal boundaries will bring chances for rain and periods of low
ceilings and visibilities beginning Monday.
surge behind departing short wave should remain below Small Craft Advisory levels this morning
although a gust or two to 20 kts across the Bay not out of the qstn
through 12z. High pressure then builds into the area through Saturday
keeping a nearly flow going at or below 15 kts.
Low pressure develops off the southeast coast Sunday night...then tracks NE
off the middle Atlantic coast Monday & Monday night. There is little to no
cold air advection in the wake of this low...so conditions should remain sub-Small Craft Advisory
with a wind becoming westerly by Tuesday. A stronger low tracks west of the
mountains Tuesday night...with a strong cold front crossing the middle
Atlantic coast Wednesday morning.