Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
843 PM EDT Monday may 4 2015
high pressure will slide farther out to sea tonight into
Wednesday. A backdoor cold front approaches from the north
Tuesday night...then drops into Virginia Wednesday into early
Thursday...before dissipating. Low pressure will spin off or near
the southeast coast Thursday into Friday.
Near term /until 6 am Tuesday morning/...
hi pressure centered off the middle Atlantic CST will provide the area with dry
and mild conditions tonight. Under a clear or mostly clear sky...min
temperatures will be in the upper 50s to lower 60s.
Short term /6 am Tuesday morning through Thursday/...
flattened hi pressure remains across the Carolinas during Tuesday...with the
center of the hi well east over the Atlantic. To the north...a backdoor cold
front will sag southward to near the Mason-Dixon by 00z Wednesday. Some
pooling moisture and vertical motion in advance of this front
could trigger a few showers and maybe a thunderstorm over northern third of the
region late Tuesday afternoon into Tuesday eveng. Thus...have 20%-30% probability of precipitation in
these areas. Otherwise...partly to mostly sunny and warm as south-southwest
winds help hi temperatures climb into the upper 70s to middle 80s.
Slight chance to chance probability of precipitation (20%-40%) will continue over northern/NE counties
Tuesday night into early Wednesday morng...due to lingering moisture/lift
sliding east-southeast alng backdoor front. Otherwise...mostly clear to
partly cloudy Tuesday night with lows in the upper 50s to lower 60s.
Wednesday through Thursday...that front will drop into Virginia before dissipating...while
weak hi pressure builds in behind it...then slides off the northern middle Atlantic
CST. At the same time...low pressure will lift nwrd off the Florida and southeast
CST. Heating combined with weak convergence and some lift alng the
frontal boundary...may trigger isolated to scattered showers or
thunderstorms...mainly over western and northern counties Wednesday afternoon into Wednesday eveng.
Partly to mostly sunny with hi temperatures ranging from the middle 70s to lower
Generally partly sunny on Thursday with a slight chance for a shower or thunderstorm
over southern/SW counties. NE or east winds will result in hi temperatures ranging
through the 70s to near 80.
Long term /Thursday night through Monday/...
medium range period highly dependent persistent upper ridge over the
east, as well as the development and eventual progress of expected
development of an area of low pressure off the East Coast of
Florida. Models are in general agreement of the development and
initial slow drift northward on Wednesday. The hurricane center is
continuing to monitor this feature for potential subtropical
development. Surface ridging to the north and west-northwest flow aloft should
force the low to meander around a position along/just off the
southeast coast through the weekend. The gefs and Euro ensembles
both continue to take the low inland along the SC/Georgia coast, as does
the new 12z/04 GFS. The operational European, meanwhile continues to
keep the system offshore. A solution towards the GFS remains the HPC
preference, and have edged the forecast in this direction. This
scenario would yield slight chance to low chance pop for mainly diurnally
driven showers/T-storms at most across our area. Lowest chances will
be across the north with surface ridging in place north of the area.
Maintained low probability of precipitation (20-30%) with the (subtropical?) Low still
meandering to the E-se. Other headline for the period will be the
warmer temperatures. East-southeast flow will bring a modest increase in
humidity, and increasing low level thicknesses favor warm highs in
the 80s under a partly to mostly sunny sky. Early morning lows look
to remain well into the 50s to middle 60s late week into early next
Aviation /01z Tuesday through Saturday/...
high pressure is centered off the middle Atlantic coast. A cold front
over the Great Lakes slowly approaches the region from the north/northwest
through Wednesday. Winds 5 to 10 knots overnight and into Tuesday
morning. The sky will be mostly clear and remain that way through
Outlook: there is a chance for thunderstorms Tuesday evening at sby. There
will be a daily chance for mainly afternoon showers and thunderstorms
Wednesday through Saturday...especially southern portions. They are
not expected to be widespread. Otherwise mainly VFR conditions are
expected during the period. Late in the week...patchy fog will be
possible around sunrise.
latest observation reflect S-SW flow 10-15kt across the waters
this afternoon west/surface high pressure oriented along/off the NC coast. Winds
have increased into the 10-15 knots range as pressure gradient has
tightend slightly in response to low pressure moves through Quebec
as high pressure remains just offshore. Still appears as if there
will likely be some gusts to 15-20 knots by tonight...but should be
too infrequent/marginal to raise any headlines in the Bay as mixing
will not be optimal (very warm airmass over relatively cool waters).
Seas in northern coastal waters 3-4 feet...2-3 feet farther south. Gradient
slackens a bit on Tuesday...then increases Tuesday night/early Wednesday as a cold
front drops south across the waters in backdoor fashion. The front
looks to gradually push into the area on Wednesday and dissipate Wednesday night
as surface high pressure builds in from the north. Combined with previously
referenced surface low off the southeast could bring a modest increase
in wind speeds as directions shift to the east/NE Thursday with tightening
pressure gradient...and have continued with a GFS weighted GFS/CMC
solution for this period. While latest wavewatch guidance shows
increase in seas for later Thursday into Friday...current track of surface low
stays too far south to bring any significant increase in seas and
winds to the local area. Will continue to monitor these trends and
any lingering coastal flood threats over the next 24 to 36 hours.