Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1001 PM EST Sat Jan 31 2015
high pressure will settle over the middle Atlantic tonight and move
offshore Sunday. Low pressure will track through the Ohio Valley
Sunday and Sunday night...and re-develop off the New Jersey coast
Monday morning. High pressure returns to area Tuesday into Wednesday.
Near term /until 6 am Sunday morning/...
no major changes necessary to the previous forecast. Did slow down the
increasing clouds tonight...but still expecting low temperatures in the low to
middle 20s across the area.
weakening high pressure will drift across the middle Atlantic and
southeast tonight. Meanwhile...a trough over the SW US will track
eastward with surface low pressure developing over the Southern Plains.
The sky will be clear this evening...with middle/high clouds
increasing from west-east after midnight as the middle-level ridge axis
moves offshore. Temperatures will drop quickly into the middle/upper
20s this evening...and then become nearly steady overnight as
cloud cover increases. One exception is the Eastern Shore where the
sky will be clear longer allowing lows to fall into the upper
Short term /6 am Sunday morning through Tuesday/...
the aforementioned system tracks through the Ohio Valley
Sunday/Sunday evening and into the central Appalachians Sunday
night...before re-organizing off the New Jersey coast midday Monday.
Locally...there is a brief period with a low chance for -sn/ice pellets across
the far northwest counties Sunday morning. This will likely not amount to
anything measurable given weak lift...but a 20% pop will be
maintained across the northwest Piedmont for now. The system actually lifts
back to the north through the day...so areas of southern Virginia/NE NC should
see temperatures rise into the low 50s without much chance for any precipitation.
Farther north...highs should be in the low/middle 40s.
Deeper moisture approaches from the west later Sunday afternoon into
Sunday evening as the surface low reaches southern in/OH. However...the
airmass remains dry below 800mb...so will only have chance probability of precipitation into
early evening for the northwest half 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/ip. Moisture
steadily increases through the night...with likely probability of precipitation west of I-95
after 03z...steadily increasing to categorical 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 north
of the area. Lows in the upper 30s/low 40s should occur in the
evening...with the current forecast indicating temperatures ranging
from the upper 40s northwest...to low/middle 50s southeast by 12z Monday.
Likely to categorical probability of precipitation will be maintained for most of the area
(aside from the far nw) through 15z Monday...with a quick drying
trend commencing from west-east thereafter. By afternoon...only chance probability of precipitation
will be continued for the eastern third of the area...with the sky
becoming partly to mostly 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 far northwest...to the middle/upper 50s across
most of the area.
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 middle teens northwest...to low 20s southeast under a mostly clear sky...and rise
into the low 30s NE...to near 40 S Tuesday under a mostly sunny sky.
Long term /Tuesday night through Saturday/...
surface hi pers 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. Quite the difference
between the 12z/31 European model (ecmwf) and GFS. European model (ecmwf) continues to suppress moisture west/
southern low pressure while GFS shows 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 rain/snow n) as colder air spreads into the region. Dry and cold
Aviation /03z Sunday through Thursday/...
as of 00z...VFR forecast through 00z with precipitation holding off to beyond 24
hours. Variable amounts of middle level clouds will cover the area
Sunday. Calm to light and variable winds overnight will become S/SW
at 5 to 10 knots during the day Sunday.
Outlook...low pressure tracks across the northern middle-Atlantic region
late Sun night-early Monday morning with the trailing cold front
sweeping across the area midday Monday. Periods of rain or showers
will affect the area Sunday night into Monday...ending from west
to east during the afternoon. Mainly dry weather is expected beginning
Tuesday. The next cold front moves through Wednesday night.
10 PM update...Small Craft Advisory no longer in effect. Seas at buoy 44009 at 850 PM
were at 4.9 feet but this is considered to be unrepresentative of the
overall condition of the coastal waters as winds continue to
diminish. Light winds are forecast across inland waters overnight
with diminishing winds in the coastal zones.
From previous discussion...
surface hi pressure drifts across the waters sun...then to the east Sun
night...result in vrb winds becoming southerly. Ahead of surface low pressure
tracking west-east through northern mdatlc region and its associated cold front...south-southwest
winds to increases Sun night...continue into Monday (to at least low end Small Craft Advisory most
places). Post cold front lt Monday into Tuesday will bring strong low level cold air advection
and either strong Small Craft Advisory conds (speeds to 30 kt) or low end gales
(gusts at or above 35 kt). Winds slo to subside Tuesday and remain sub-Small Craft Advisory Wednesday.