Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Wakefield Virginia
1037 am EST Sat Jan 31 2015

cold high pressure builds into the region today. Low pressure
will track east from the Ohio Valley on Sunday...and push off the
New Jersey coast Monday morning. High pressure returns to area
Tuesday into Wednesday.


Near term /until 6 PM this evening/...
the current surface analysis indicates ~1032mb high pressure
centered over the Cumberland Plateau...which extends eastward over
the southeast coastal plain...and a trough is present to the Lee-
side of the Blue Ridge over VA/NC. Cold air advection lingers this morning over
the Eastern Shore producing wind gusts to 20-25kt out of the northwest.
Temperatures have risen into the middle 20s to low 30s as of 10 am.

High pressure builds east and will become centered along the
Carolina coast by midday. A northwest wind will remain gusty from the northwest
over the Eastern Shore. Otherwise...the wind will diminish through the
day. Sunny today...but cold with highs topping out in the Lower-
Middle 40s across south central Virginia and interior NE NC to the lower 30s
on the Maryland Eastern Shore.

Temperatures drop fast this evening...then become nearly steady. Clear
skies/light flow...followed by increasing middle/high clouds overnight.
Lows tonight in the upper teens/lower 20s NE to the Lower-Middle 20s


Short term /6 PM this evening through Monday/...
NAM/GFS/ECMWF into better agreement west/ the handling of the upcoming
storm system. A more northern track prevails...with surface low pressure
pushing from the Ohio Valley through PA/New Jersey Sun night/Mon. There is
a brief period with a low chance for -sn/ice pellets across the far northwest counties
Sun morning. This will likely not amount to anything measurable
given weak lift but will have a 20% pop across the northwest Piedmont for
now. The system actually lifts a bit 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. By late afternoon/early evening...deeper
moisture approaches from the west as the surface low reaches southern
in/OH. Still only a chance pop for areas along/east of I-95 through
03z...with likely probability of precipitation west of I-95 from 00z-03z. Thicknesses support mainly
rain throughout the County Warning Area...but will go with a rain/ice pellets mixture at
onset of precipitation during this timeframe due to dry air (dew points in
20s) even as surface temperatures remain well above 32 f (in the 40s). Expecting
moderation of the airmass over the forecast area as S winds develop overnight. Thus...rain
will be the only forecast p-type Sun night into Monday morning. Temperatures to
bottom out early sun evening (in the u30s north...l/m40s s)...then rise
thereafter into Monday morning (into the 50s across southeast Virginia..40s elsewhere).

By midday/afternoon Monday...drying trend begins...GFS a little faster
than the NAM/European model (ecmwf) solutions but only by a few hours. Have trimmed
back on probability of precipitation in the afternoon over interior Virginia and NC and should see
partly sunny skies. Best chance for afternoon precipitation looks to shift to NE
zones. Due to warm start to the day...think cold air will struggle
to make it into akq County Warning Area before sunset. Will carry just rain as
ptype in the afternoon except across the far north after 21z. Hi temperatures from the
middle/upper 40s north-northwest to the upper 50s southeast.


Long term /Monday night through Friday/...
other than some some lingering clouds over coastal waters Erly Monday
evening...expect clearing skies and cold Monday night as 1030+ mb high apprchs
forecast area from the Ohio Valley. Lows in the middle teens north to l20s
south xcpt m20s southeastern beach areas.

Ridge axis moves ovrhd Erly Tuesday then shifts offshore. Mostly sunny
and cold. Highs in the 30s. Mostly clear Tuesday night. Lows in the 20s.

Models continue to have difficulty with middle week systm and offer
up different timing and moisture a low confidence
forecast continues until more model agreement can be seen. However...
the trend is slower in bringing moisture north into the forecast area as southern
stream low develops in the northern Gulf of Mexico then tracks NE along
the southeast and possibly middle atlntc coast before pulling NE and away from
the area. Model guidance suggests leaning more toward the GFS solution.
Trended drier/warmer on Wednesday with highs in the 50s. Expect increasing
cloudiness Wednesday night. Went with low chance probability of precipitation across NC counties Wednesday night.
Chance (liquid) probability of precipitation Wednesday night with only about a 20% pop for mixed
snow/rain late across northern most counties. Lows around freezing northern most
counties to the M-u30s over the south. Rain chances continue Thursday xcpt for
some rain/snow mix across the north. Colder...with highs in the
middle 40s southeast to the 30s over the north.

If the 00z European model (ecmwf) verifies...the strong high prs keeps southern stream low
south with little if any impact on forecast area. This has been the case most
of this winter given no real blocking pattern seen. Its solution would
be colder and drier.

Anthr Arctic high pressure builds into the area from the northwest behind
this systm by Friday. Decreasing cloudiness Thursday night. Lows in the 20s. Mostly
sunny Friday. Highs in the 30s.


Aviation /15z Saturday through Wednesday/...
northwest winds have diminished inland this morning at or below 10 knots thanks to
high pressure building in from the west. However...gusts of 25 to 30
knots persist near the coast. Otherwise...dry/skc conditions prevail
through the morning. High pressure builds over the area today with
inland winds remaining at or below 10 knots. Northwest gusts of 20-25 knots expected to
persist through the afternoon near the coast. Sky clear conditions expected
through the afternoon...but high clouds begin to stream into the region
as the next storm system approaches.

Outlook...high pressure slides offshore sun as low pressure
approaches from the west. Low pressure tracks across the northern
middle-Atlantic region late Sun night-early Monday morning with the
trailing cold front sweeping across the area Monday morning.
Widespread rainfall will accompany the front with IFR ceilings/visibilities
possible. Rain ends Monday afternoon. High pressure/fair weather
returns Tuesday and Wednesday. The next cold front approaches the region
from the northwest Wednesday night.


replaced gales with sca's with 10 am update. Winds/seas will
continue to diminish this afternoon as high pressure builds into
the area from the west. Also cancelled the freezing spray advisory
as temperatures slowly warm as winds diminish over the next several hours.

Previous discussion... latest weather analysis over the waters
depicts last evenings cold front well offshore with high pressure
building eastward over the Ohio Valley. Strong pressure gradient in
tandem with low level cold air advection has resulted in gale conditions across
the Bay and coastal waters early this morning. Thereafter...cold air advection
wanes as high pressure begins to build over the waters. Low level
winds also subside below 30 knots. However...Small Craft Advisory conditions persist
through the morning before high pressure finally builds over the
waters and the pressure gradient relaxes this afternoon. 6-9 feet
seas will persist through early morning...before slowly subsiding
through the day and finally dropping below 5 feet all coastal waters
this evening. High pressure slides offshore tonight with southerly flow
at or below 15 knots returning to the waters. Southerly flow increases Sun night as
low pressure and an attendant cold front approach the waters. The
front crosses the waters Monday morning...followed by another strong
northwesterly surge. A period of gales is expected Monday night for the Bay
and coastal waters. Seas builds to 6 to 9 feet. High pressure
returns Tuesday and Wednesday in advance of the next cold front set to
cross the waters Wednesday night.

Have expanded the freezing spray advisory to include the Bay and
coastal waters north of the NC/Virginia border as temperatures have fallen at or below 25
degrees. Moderate icing is expected through middle morning. Freezing spray is
expected again Monday night as air temperatures over the water drop into the
low to middle 20s in tandem with strong northwest gusts.


Akq watches/warnings/advisories...
Marine...Small Craft Advisory until 1 PM EST this afternoon for
Small Craft Advisory until 4 PM EST this afternoon for
Small Craft Advisory until 7 PM EST this evening for anz650-


near term...lkb/ajz
short term...alb/lkb
long term...lkb/mpr

National Weather Service Glossary of Abbreviations