Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
959 am EST Sat Feb 28 2015
Arctic high pressure remains over the region through
tonight...then slides offshore Sunday. Low pressure tracks
northwest of the area Sunday and Sunday night. The trailing cold
front pushes across the region Monday morning.
Near term /until 6 PM this evening/...
1045mb surface hi pressure has settled over the forecast area the past 12 hours...and
will remain so through the rest of the day. Broken-overcast ceilings mainly at or above
10kft expected the rest of the day...so will have vrb clds-psny.
Despite strengthening sun (at this time of yr)...temperatures will remain
nearly 20-25f below normal...W/ most hi temperatures from the l/m30s. North-northeast winds
will average 10 miles per hour or less inland...10-15 miles per hour near the CST.
Short term /6 PM this evening through Monday/...
ridge axis moves east of the area tonight. Clouds quickly overspread
the area ahead of next systm apprchg from the west. The clouds will
likely prevent temperatures from reaching the record lows for the date (see
climate section blo). Dry through 12z sun. Lows middle teens to l20s.
Low pressure ejects NE from nations middle section sun with assctd
warm front lifting northward across the forecast area. Yet another challenging
forecast as the latest models show light precipitation breaking out across
northwestern half of forecast area Sunday morning before the cold air dislodges making
for p-type issues. Low level thicknesses along with surface temperatures at or below
freezing will make for a winter mix of precipitation at onset before temperatures
rise above freezing changing precipitation to plain rain. Models offer up
different solutions on where these p-type issues will be but will lean
toward a sref solution which seems to be a compromise at this time.
Grids will Show Low chance probability of precipitation for a mixture of snow/sleet/fz rain
across areas west of i95 corridor between 12-15z...then chance probability of precipitation mainly
north of a wal-fyj-ptb-avc line between 15-18z. Only slght chance probability of precipitation
southeast of there where precipitation should be rain.
Data then supports temperatures warming up enough for precipitation to change over
to rain after 18z across the forecast area. Tricky part will be across far northwestern
counties (louisa/fluvanna) where historically The Wedge is harder to
break. Highs occur late and range from the m30s western most counties to
the l-m40s southeastern areas. Confidence not high enough to issue any third
period advisory given rather low quantitative precipitation forecast and model differences. Will
mention a possible morning mix across northern half of forecast area in the severe weather potential statement.
Chance to likely probability of precipitation Sunday night. Precipitation in liquid form as temperatures hold
steady or slowly rise to the M-u30s.
Low pressure tracks into New England Monday...with the trailing cold
front pushing across the forecast area during the morning hours. Kept chance probability of precipitation
with the frontal passage at this time. How quickly the front exits Monday afternoon will
determine any clearing taking place W-E. Highs ranging from the m40s
Eastern Shore areas...u40s-l50s west of the ches Bay.
Long term /Monday night through Friday/...
high pressure builds into the region Monday night. The flow aloft is
zonal...so only partial clearing is expected. Lows should range from
the middle/upper 20s north...to low 30s S. The high shifts offshore Tuesday
as low pressure tracks into the Ohio Valley. The attendant warm
front lifts through the region later Tuesday into Tuesday night. The
best forcing for precipitation will track north of the region...so the highest
probability of precipitation will be across northern portions...with a lesser chance to the S.
Tuesday should be cloudy and cool with most of the area within a
residual cad-wedge. Highs should range from around 40 northwest...to near
50 southeast. The current forecast should lows only dropping a few degrees
Tuesday evening...before rising overnight. 27/00z and 12z runs of
the European model (ecmwf) suggest the potential for highs well into the 70s
Wednesday. However...the GFS has been consistently quicker with the
frontal passage and hence has more cloud cover/higher potential for
-ra. The 27/12z CMC is closer to the European model (ecmwf). At this time...highs
have been trended upward into the low/middle 60s away from the
coasts...which reflects a consensus model blend. GFS/European model (ecmwf) each have
the front through the region by Thursday...with anafrontal precipitation in
its wake. The airmass behind this front is once again Arctic in
origin. The question in whether or not the cold air will come in
quick enough to produce a changeover to -sn (primarily north/northwest
portions). This portion of the forecast is considered low confidence
at this time...so no mention of -sn will be included. Temperatures
are expected to be well below normal again by later next week with
current forecast highs in the upper 30s to middle 40s...with lows in
the low/middle 20s Thursday/Friday nights.
Aviation /15z Saturday through Wednesday/...
VFR conditions will persist through the 12z taf period as high
pressure builds over the area.
Moisture returns to the local area Sunday morning in the presence
of a retreating cold airmass. This will pose a threat for light
-fzra/-pl at kric...ksby...and potentially kphf from roughly 12z-18z.
Light rain lingers all taf sites after 18z. Dry weather returns by Monday.
have allowed the Small Craft Advisory for the coastal waters north of Cape Charles
to expire as of 6 am...with seas below 5 feet. Minimal Small Craft Advisory
conditions continue across the southern ches Bay/Currituck Sound at this time
with north-NE winds 15-20 knots. Will keep Small Craft Advisory going south of new pt
Comfort and the sound through 10 am. Elsewhere...NE winds will
allow seas to remain 5-7 feet across the southern coastal waters
until later this afternoon...and thus will keep Small Craft Advisory going until 4 PM
south of Cape Charles. High pressure builds over the waters
tonight and shifts offshore Sunday...with a cold front moving
through the region Monday morning...followed by a brief northerly
surge. High pressure returns Monday night...with low pressure
approaching from the west late Tuesday allowing the wind to become
south-southwest Tuesday night into Wednesday.
records at Richmond and Norfolk date back into the late
1800s...with some notable top ten ranks in snow and temperature
Average temperature for February through the 27th:
Richmond: 31.5 f (-9.3 from avg). This would rank as the 6th
coldest Feb on record and the coldest since 1979.
Norfolk: 32.6 f (-9.9 from avg). This would tie the 3rd coldest
Feb on record and the coldest since 1978.
Snowfall for February through the 27th:
* richmond: 12.2" (snowiest Feb occurred in 1983 with 21.4"). This
moves Richmond up to #9 all time for Feb.
* Norfolk: 11.5" (snowiest Feb occurred in 1989 with 24.4"). This
moves Norfolk up to #7 all time for Feb.
Another round of cold weather is expected this weekend.
Record low temperatures (sunday morning):
3/1 all time record low temperatures for March
ric11/1937 10 March 4 2009
orf18/1980 14 March 14 1888
sby 13/1980 1 March 3,4 2009 and March 9 1911
ecg 16/1937 16 March 1 1937 and March 4 1943
Record low high temperatures (today):
Marine...Small Craft Advisory until 4 PM EST this afternoon for anz656-
Small Craft Advisory until 10 am EST this morning for