Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1033 am EST Tuesday Mar 3 2015
high pressure will slide offshore this afternoon. A warm front
lifts northeast across the region tonight...followed by a cold
front slowly crossing the area Wednesday afternoon through
Near term /through tonight/...
late this morng...hi pressure was centered right along the CST. Flow
aloft is generally from the west...well out ahead of broad trough over
the western Continental U.S.. temperatures were slowly climbing through the 30s to near 40
degrees over the akq County Warning Area...with dewpoints ranging from the middle teens to
the upper 20s. Radar showed only very light mixed precipitation or rain over the
mountains of West Virginia and SW Virginia. Center of hi pressure will push offshr this
afternoon...but low level cad remains over the forecast area. A cloudy sky will
limit temperature rises this afternoon...with highs only ranging from the middle
30s extreme northwest to the middle 40s over NE NC. Better coverage of precipitation is
expected middle/late afternoon...with best precipitation chances (50-60%) for mainly
light rain across northern and western areas. Model soundings continue to
support a brief period of -fzra over far northwest areas between 16-20z
as temperatures struggle to reach/surpass 32f through early this afternoon.
Confidence remains low at this time given marginal temperatures and a warm day
yesterday. Otherwise...p-type to be all rain over the region this
Short term /Wednesday through Thursday/...
warm front to lift NE through the forecast area tonight. Best moisture and
uvm across central/northern portions of forecast area...thus the highest probability of precipitation...W/
with chance probability of precipitation limited to southern Virginia/NE NC. Bulk of the rain lifts to northern
portion by lt at night. Low temperatures likely around 00z/04 with rising
temperatures through the night. Temperatures by 12z/04 Wednesday rise into the middle/upper
40s to middle 50s southeast.
Forecast area becomes "warm sectored" Wednesday due to surge of a strong south-southwest flow.
There remain timing issues west/ the approaching cold front from the north-northwest...however
a GFS/European model (ecmwf) blend looks like a good compromise. Will have highest probability of precipitation
(40-70%) by afternoon across northern tier of forecast area...W/ slight chance to chance (20-40%)
to the S. For now...leaving out any mention of T across southern Virginia/NE
NC...since it aprs most of moisture confined to west/ and behind the
fnt. Hi temperatures from the u50s/l60s north to l70s in far southeast Virginia/NE NC.
Just one year ago...March 2nd-3rd...went from 60s to l70s (the 2nd)
to a few inches of snow (on the 3rd). This may occur again this weak
Forecast challenges continue Wednesday night through Thursday as cold front settles south-southeast
through the forecast area...and another area of Arctic surface hi pressure builds toward
the MS/Ohio valleys. Will lean toward the faster arrival of colder surface
air from the north-northwest (gfs/ecmwf) by lt Wednesday night and continuing on Thursday. The
models each hint at weak surface low pressure tracking through NC as short wave aloft
(in fast southwesterly flo) is sheared as it moves eastward into the region. All
this leads to a transition (wrt p-type) lt Wed/Thu. Rain...becomes
mixed west/ ice pellets-changing to snow/ice pellets then ending as snow from north-northwest to southeast across
the forecast area (lastly across NE NC by middle or lt afternoon thu). Timing those
transitions at this point very difficult...though currently expect
a least light snow accums for areas north of the NC/Virginia border before the
day ends Thursday (t-2 inches S...1-4 inches north (highest ptnttly from
ric-sby)). Along west/ the transition to wintry precipitation...gusty north-northeast winds
will be pushing colder air into the region. Low temperatures Wednesday night from around
30f north to the low/middle 40s far S. Temperatures Thursday steady or falling.
Long term /Thursday night through Monday/...
cold to begin the extended in wake of Thursday cold front...but
moderating temperatures through the weekend will bring temperatures back to near
normal early next week.
Shortwave pushes offshore Thursday night with the northern portion of the
front pushing well offshore. Southern portion pushes southward over the Gulf
states/northern Gulf...stalling in westerly flow aloft. Ended chance probability of precipitation near
the coast at midnight...with drying/clearing conditions thereafter.
1030+mb Arctic high pressure builds over the region Friday...resulting
in another cold day with highs around 20 degrees below normal. 850 mb
temperatures bottom out around -12c (-2 Standard dev)...with thicknesses
yielding temperatures in the low-middle 30s. Surface high pushes offshore Friday
night with light return flow helping moderate low level thicknesses.
Temperatures forecast in the middle-upper teens Friday night under mostly clear
skies. Thereafter...medium range guidance begins to diverge thanks
to developing split flow over the western Continental U.S.. the upper pattern will
again be characterized by cyclonic flow (troughing) over the eastern
Continental U.S. And ridging (return to a +pna) over the western Continental U.S.. models
struggling with a number of Canadian impulses set to impact the NE
states...but also southern stream energy over the Baja California this weekend.
European model (ecmwf) rather robust with this energy...translating across northern Mexico
and the Southern Plains Sat night-sun...possibly phasing with northern stream
energy over the Midwest. This solution would lift the stalled
frontal boundary over the Gulf northward late in the weekend...bringing
rain to the region early next week. The GFS shears the
energy...keeping it well south of the region...keeping the local
area dry. Have trended forecast toward a wpc/ensemble approach which
keeps the southern stream wave flat and the local area dry through the
weekend..with moderating temperatures. Highs Sat forecast in the upper
40s-low 50s inland and low-middle 40s near the coast. Highs sun in the
middle 50s inland and middle-upper 40s near the coast.
Aviation /15z Tuesday through Saturday/...
scattered-broken high clouds should continue to pass over the region
overnight...with a light north-northeast wind due to 1030mb high pressure over
PA. One exception will be ecg...which will have a period of 5kft
ceilings over the next few hours. High pressure moves offshore
today...followed by a warm front tonight. A period of -ra is
expected to develop later this afternoon...primarily after 21z.
Ceilings lower to 4-5kft through the day along with a light east-southeast wind.
There is an increasing potential for IFR ceilings tonight...especially
after 06z as the warm front lifts through the region. Conditions
should improve for a brief period later Wednesday morning.
However...a cold front is expected to drop through the region
during the afternoon followed by deteriorating flight conditions.
The chance of rain increases later Wednesday afternoon...with rain
overspreading the entire region Wednesday evening. A transition to
a mix and eventually snow should begin at sby after 06z...with the
transition occurring at ric closer to 12z. Farther southeast...the change
should occur later in the day. Additionally...a gusty northerly
wind will develop along the coast Thursday. High pressure settles
over the area Friday and Saturday.
1030mb surface high pressure shifts offshore today allowing a
10-15kt north-northeast wind to become southeast at or below 10kt by afternoon. The high shifts
farther offshore tonight as a warm front lifts through the region.
Despite a strong low level jet it will be difficult to obtain Small Craft Advisory conditions
given warm air advection over cold water. Given this...wind/seas have been capped
below Small Craft Advisory criteria. Overall...expect a south-southwest wind ~15kt for the Bay
and a 15-20kt for the ocean along with 3-4ft seas/2-3ft waves. A
cold front approaches from the north-northwest Wednesday morning...and slowly
drops to a position near the Virginia/NC border by late afternoon/early
evening. The front then becomes nearly stationary Wednesday night as
low pressure tracks along the boundary. Cold air advection commences Thursday as
the low pulls offshore and continues into Thursday night as 1040mb
high pressure builds in from the northwest. Small Craft Advisory conditions are likely
during this time period with a northerly wind of 20-25kt...and 4-7ft
seas (highest s) and 3-4ft waves in the Bay. High pressure returns
Friday and Friday night...and slides offshore Saturday.