Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
400 am EDT Friday may 29 2015
high pressure will build over the northeast states today...then
slide off the coast Saturday. A slow moving cold front will enter
the local area from the northwest late Sunday...and stall across
the region on Monday.
Near term /through tonight/...
current analysis indicates a surface cold front extending SW into the
northern middle Atlantic region from low pressure off the New England
coast. WV satellite shows shortwave energy trailing the surface low tracking
east to the coast of Maine. Weak upper ridge is still in place
over the local area...but the presence of the front has set off a
cluster of thunderstorms over the lower Eastern Shore just to the north of
Dorchester Maryland. Farther south a weak low level convergence boundary
has been enough to set off widely scattered showers over southeast Virginia.
Will carry 20-30% probability of precipitation through 12z to account for this. Elsewhere...variably
cloudy with temperatures in the middle 60s to around 70 f through daybreak.
For the rest of today...expect early am clouds to scatter out and
leave mainly dry weather for the rest of the morning/early afternoon. Models
show a slight drop in dewpoints across the forecast area as hi pressure just offshore
begins to slightly build westward during the day. Focus of higher probability of precipitation
(30-40%) shifts to far northwest portion of forecast area with only 10-20% probability of precipitation
elswhere. Slightly cooler than yesterday with highs in middle-upper
80s well inland...to the middle 70s to lower 80s at the coast.
Becoming mostly clear tonight with lows in the 60s to around 70 f.
Short term /Saturday through Sunday/...
our period of Summer-like weather to continue through the weekend. 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 generally only 10%.
Cold front from the northwest continues to slowly approach sun. Much of the day will
be p/msny. Will increases probability of precipitation to 40-50% far north-northwest portions of the forecast area
for the late 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 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 /08z Friday through Tuesday/...
high pressure remains over the western Atlantic this morning.
Calm-light S wind at or below 5 knots will persist. Middle level moisture will
result in a few-scattered deck around 5k feet above ground level...with scattered-broken high
clouds at or above 25k feet above ground level through 12z. MVFR visibilities expected over the
Piedmont and portions of southeast Virginia (areas that received rainfall)...but
do not anticipate fog at the taf sites. Scattered-broken deck around 2500
feet above ground level possible 10-12z kric/ksby.
For today...a southeast wind of 5-10 knots prevails as high pressure remains
well offshore. Scattered afternoon cumulus with decks 4-5k feet above ground level expected.
Isolated to widely scattered showers/thunderstorms expected over
the Piedmont into central Virginia...but taf sites expected to remain dry.
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.
latest observation over the water reflect southerly winds at or below 10 knots. Waves 1-2 feet
and seas 2-3 feet. High pressure remains over the western Atlantic through
the weekend. The result will be continued sub-Small Craft Advisory conditions. A southeasterly
wind averages 10-15 knots today. Gradient strengthens tonight into
Saturday as a cold front moves into the Great Lakes region. Southeasterly
winds increase to a solid 15 knots...pushing seas to 2-3 feet Sat and 3-4
feet Sat night. Waves build to 2-3 feet. Flow becomes southerly 10-15 knots
sun...before the flow weakens Sun 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.