Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
400 am EST sun Feb 1 2015
high pressure will slide off the North Carolina coast today...as
low pressure over the middle Mississippi Valley moves east. This low
will push from Ohio into Pennsylvania tonight...and re-develop
off the New Jersey coast Monday morning. High pressure returns to
area Tuesday into Wednesday.
Near term /until 6 PM this evening/...
current analysis depicts ~1028 mb surface high pressure centered just
off the southern NC coast...with deepening surface low pressure over
eastern Kansas. WV satellite reveals a digging shortwave trough
over Colorado...and this will phase with a downstream shortwave
over Nebraska later today to help drive the surface low east-northeast through
the day. Over the local area...skies have started to cloud up with
ceilings of 10-15k feet. Temperatures have started to rise a few degrees
with a light south wind...but remain mainly in the 20s to lower
30s. Coldest section of County Warning Area is the Eastern Shore where winds are generally
calm and under clear skies readings are in the teens to lower 20s.
Not much change to forecast reasoning today...surface low in the
Midwest has a long way to travel before reaching the East Coast...so
little in the way of forcing for anything more than clouds today.
BUFKIT soundings show ample middle level moisture through the day so
skies should average out cloudy to mostly cloudy. A light south-southeast wind of
5-10 miles per hour will boost temperatures today...with a fairly mild afternoon
expected. Went with a blend of mav/met MOS for highs into the
Lower-Middle 40s far north...to the lower 50s south.
Short term /6 PM this evening through Tuesday/...
for this evening...deeper moisture is slow to reach east of the
mountains as surface low at 00z will only be as far east as central Indiana
or western Ohio. The airmass remains dry below 800mb...so will
only have low chance probability of precipitation into early evening for the northen and
western portions of the area. Partial thicknesses support rain
throughout the evening...but given the dry air initially...the
onset of precipitation could be a mix of -ra/ice pellets (although with surface temperatures
in the upper 30s to middle 40s no impacts will occur). Moisture
steadily increases through the night...with likely probability of precipitation reaching
northern and western zones between 03-06z...steadily increasing to
categorical (80-90%) for all areas after 09z. The surface airmass is
expected to modify through the night as southerly flow develops
across the region due to the low tracking well north of the area. Lows in
the upper 30s/low 40s should occur in the evening...with the
current forecast indicating temperatures rising into the middle-upper
40s northwest...to low/middle 50s southeast by 12z Monday.
Likely to categorical probability of precipitation will be maintained for all of the area
from 12z to 15z Monday...and in far southeast sections this may be the
period of most significant rainfall. A quick drying trend
commences from 15-18z although trends are a tad slower than
previous models had indicated. After 18z...only chance probability of precipitation will be
continued for the eastern third of the area...with the sky becoming
partly sunny over interior VA/NC. The day will begin warm...and
cold air advection will likely wait until after sunset...so highs should range
from the upper 40s/around 50 f far northwest...to 55-60 f across most of
Deep layer northwest flow prevails Monday night...and backs to westerly
Tuesday. This will allow surface high pressure (and associated caa)
to build into the region Monday night...with the high locating along
the coast by Tuesday afternoon. Lows Monday night should fall into
the upper teens northwest...to low-middle 20s southeast under a mostly clear sky.
Cold Tuesday as surface high builds into the region with highs in the low-middle
30s NE...to the lower 40s SW under a mostly sunny sky.
Long term /Tuesday night through Saturday/...
surface hi pressure drifts off the CST Tuesday night into Wednesday...resulting in
milder weather midweek. Cold front approaches from the north-northwest Wednesday...then slowly
settles S across the area Wednesday night through Thursday...while at the same
time surface low pressure tracks east in vicinity of Gulf Coast states. Still some
difference between the latest European model (ecmwf) and GFS...although they are
slowly coming into better agreement. European model (ecmwf) continues to suppress
moisture west/ southern low pressure while GFS shows some moisture (and ptntl
p-type issues) into/across the forecast area (on thu) before departing Thursday night.
Will go west/ consensus from HPC...and have widespread cloudiness and chance
probability of precipitation (ra S...mixed snow or rain/snow n) as colder air spreads into the
region. Dry and cold Fri/Sat.
Aviation /09z Sunday through Thursday/...
high pressure over the region this morning has resulted in dry
conditions and calm-light winds. A storm system approaching from the
west will begin to stream broken middle-high clouds into the region this
morning...varying from 12-15k feet above ground level. For today...high pressure
drifts offshore. Variable amounts of scattered-broken middle level clouds with
decks 10 to 15k feet above ground level will cover the area today. May also see a
few-scattered deck around 5k feet above ground level from kric to ksby. Winds become S-southwesterly
generally at or below 10 knots.
Skies become overcast this evening as the approaching surface low lifts into
the Ohio Valley. The trailing cold front reaches the local area late
tonight into early Monday morning. Precipitation will begin to spread over the
Piedmont this evening...reaching kric and ksby by late this evening.
Have opted to trend sky cover to MVFR and introduce -ra br at kric
and ksby as a result.
Cold front sweeps through the local area Monday morning...pushing offshore
Monday afternoon. Rain will accompany the front...but is expected to
remain light. Guidance suggests best chances for IFR will be from
ceilings along and in advance of the front. Visibilities look to be generally
MVFR at this time. Conditions improve Post frontal with clearing skies late
Monday-Monday evening. High pressure returns tues-weds. The next cold
front crosses the region Wednesday night-Thursday morning.
high pressure over the waters has resulted in light and variable
flow this morning with speeds at or below 10 knots. Waves generally 1-2 feet and
seas 2-3 feet...and subsiding. High pressure slides offshore tonight
as low pressure and a trailing cold front approach from the west.
The low will lift north of the waters with the front sweeping through
the region Monday morning-afternoon. Southerly flow increases in advance of
the front with Small Craft Advisory headlines in place beginning tonight in the
Bay/rivers/sound for gusts up to 25 knots. Seas will build to 4-6 feet
late tonight-early Monday morning in the coastal waters as southerly winds
increase to 20-30 knots. Headlines begin late tonight for all coastal
waters. Seas build to 5 to 7 feet Monday afternoon with waves 3-4 feet.
Cold front crosses the waters Monday afternoon...with flow becoming west
to northwest Post frontal. Strong cold air advection will kick in Monday evening in tandem
with increasing gradient winds. The result will be a period of gale
conditions over the Bay and coastal waters Monday night. A gale watch
has been hoisted as a result. Gusts of 35-40 knots expected over the
Bay and coastal waters and gusts of 30 knots in the rivers and sound.
Seas forecast to build to 6-10 feet Monday night. Freezing spray also
expected Monday night as temperatures over the waters drop into the low-middle
High pressure builds into the region late Tuesday night with winds
diminishing through Tuesday morning. Winds will drop below Small Craft Advisory Tuesday
morning all waters...with seas subsiding to 4-6 feet. Seas expected to
drop below 5 feet Tuesday afternoon. High pressure remains over the
waters Tuesday and Wednesday with the next cold front set to cross the
waters late Wednesday night. Small Craft Advisory conditions are anticipated.
Marine...Small Craft Advisory from midnight tonight to 6 PM EST Monday
Gale watch from Monday evening through late Monday night for
Small Craft Advisory from 4 am to 6 PM EST Monday for anz650-