Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
949 PM EDT Thursday may 28 2015
high pressure remains anchored well off the middle Atlantic coast
overnight...with a trough of low pressure nearly stationary east
of the mountains. High pressure will build over the northeast
states Friday...then slide off the coast Saturday. A slow moving
cold front will enter the local area from the northwest Sunday
Near term /until 6 am Friday morning/...
a weak shear boundary aloft and a myriad of convective outflows evident
on Sat/radar allowed for isolated to widely scattered pulse
convection to develop earlier this afternoon. This activity has waned
as expected with loss of heating. Have cut probability of precipitation to 20% (mainly northwest
piedmont) or less for the balance of the overnight. Brief
clearing early tonight will give way to increasing low stratus
overnight, especially in areas where rain has fallen. Cloud cover
averages out partly to mostly cloudy. Early morning low temperatures
Short term /6 am Friday morning through Sunday/...
our period of Summer-like weather to continue through the weekend. Weak surface hi pressure
slides east across new eng Friday. Models show a slight drop in dewpoints across
the forecast area beginning Friday as hi pressure just offshore begins to slightly
build westward during the day. So focus of higher probability of precipitation (30-40%) northwest 1/2
of forecast area with only 10-20% probability of precipitation elsewhere. By Sat...cold front pushes southeast through
the Ohio Valley...remaining far enough away for any significant impact on
the weather here. Will keep conds warm west/ vrb clouds/pcldy west-northwest and mainly
sky clear toward the CST. Probability of precipitation 20% pop inland...10% at the CST.
Cold front from the northwest continues to slowly approach sun. Much of the day will
be p/msny. Will increases probability of precipitation to 40-60% far north-northwest portions of the forecast area
for the afternoon/evening hours...tapering to 10% in far southeast Virginia and NE NC. The
bulk of precipitation expected to be along and behind the fnt (and that is not
likely until lt sun).
Hi temperatures Friday in the M/u80s inland...70s at the CST. Low temperatures Friday
night M/u60s. Hi temperatures Sat and sun from the u80s to around 90f
inland...70s to l80s at the CST.
Long term /Sunday night through Thursday/...
middle/upper ridging persists over the middle Atlantic and southeast
coasts Sunday night and Monday...with a trough over the
Mississippi Valley. 12z/28 GFS/European model (ecmwf) each indicate the trough
closes off in vicinity of the Gulf Coast Monday night and
Tuesday...with the ridge retrograding west. Meanwhile...a trough will
dig across the northeast Monday through Tuesday...which will allow
for a surface cold front to drop into the region Monday and push
into the Carolinas Tuesday. The GFS remains more aggressive with
the southward movement of the front...but the European model (ecmwf) does still
push the surface boundary through the area by Tuesday. Surface
high pressure over New England Wednesday will nudge into the
region by Thursday...as middle/upper ridging returns as the trough
moves offshore. Probability of precipitation average 30-50% Sunday night through Monday
night with the surface cold front over the middle Atlantic...then
tapering off Tuesday afternoon and evening as the high builds in
from the north-northeast. Drier conditions are expected by Wednesday and
Thursday with high pressure building into the region. Warm and
humid conditions continue Monday with highs ranging from the middle
70s north...to low 80s S. Cooler Tuesday and Wednesday behind the
front with onshore flow. Currently will forecast highs ranging
from the low 70s north to near 80 S...but these values could be cooler
depending on clouds and precipitation. Temperatures should begin to
increase Thursday. Lows should average through the 60s.
Aviation /02z Friday through Tuesday/...
stagnant weather pattern of last few days will continue through Sat
with surface hi pressure offshore and low pressure well west of the middle Atlantic. S
winds at 5 knots will continue after dark. Patchy fog/stratus is possible
over areas that receive rainfall...but VFR conds should prevail at
the taf sites tonight.
Upper/surface high pressure remains over the region into the weekend.
Dry conditions are expected to prevail...but there is a chance for
diurnally driven showers/thunderstorms across the Piedmont Friday-
Sat. Better chances for precipitation expected sun-Monday as a cold front
reaches...and then stalls over the region.
high pressure remains centered off the middle Atlantic coast through
Saturday. A weak cold front passes just north of the region tonight
and washes out Friday. A southerly wind should average 10-15kt
this evening and diminish to 5-10kt late tonight into Friday
morning as the gradient slackens. The gradient tightens Friday
night into Saturday as a cold front moves into the Great Lakes
region. A south-southwest wind of 10-15kt is expected Friday night into
Saturday...with a solid 15kt possible later Saturday afternoon and
evening. Seas should average 2-3ft...with 1-2ft waves in a
southerly flow regime. A 10-15kt southerly wind should continue
Sunday before the flow weakens Sunday night into Monday as the
cold front settles into the region. High pressure builds in from
the NE Monday night through Wednesday. Expect increasing NE flow
and building seas/waves with onshore flow.