Scientific Forecaster Discussion
fxus61 kakq 222327
Area forecast discussion
National Weather Service Wakefield Virginia
627 PM EST Mon Jan 22 2018
high pressure remains centered off the mid Atlantic coast
today. A trough crosses the region Tuesday morning, with the
cold front lagging behind and pushing through the region by late
afternoon. Es well off the coast by Tuesday night. High
pressure becomes centered over the south central states
Wednesday and builds east into the local area by Thursday.
Near term /through Tuesday/...
latest analysis places a potent sfc low ~995mb moving into the
mid/upper MS valley with cutoff upper low lagging back a bit to
the SW acrs Missouri. Meanwhile, sfc high pressure remains off
the mid- Atlantic coast with dry/warm conditions over the local
area. Temperatures this aftn have warmed well into the 60s for
most of the County Warning Area with the exception of the coastal Eastern Shore
and NC Outer Banks where it's mainly in the 50s. Fairly thick
cirrus shield remains in place for the most part, though some
thinning of the clouds likely over southern portions of the County Warning Area
through 00z. Dry/very mild tonight with temperatures staying
in the 50s just about everywhere (mid/upper 40s coastal Eastern
Shore/VA beach/NC outer banks). Partly/mostly cloudy in the
evening, then becoming cloudy overnight with increasing rain
chances after 06z mainly over the Piedmont, and will overspread
likely pops to the I-95 corridor between 09-12z. Enough mid
level instability will move in late to include mention of
isolated tstms late west of I-95, though at this point these
will be elevated.
High rain chances (60-90%) prevail Tue morning as main sfc low
pressure becomes occluded over Michigan and significant pressure
falls and a meso-low develop along the central Appalachians by
around 12z. The strength of this feature will likely have a
significant affect on quantitative precipitation forecast and the potential for some embedded
convection in the morning in a high shear/minimal cape
environment. Latest GFS/NAM sherb values are from +1 to +1.5
between 12-18z, though this parameter does have some limitations
and the synoptic pattern (sfc low into great lakes), does not
typically favor a lot of tstms/severe threat for the akq County Warning Area.
However, with significant shear and some instability aloft
(h7-500 mb lapse rates of 6.5c/km) can't rule out isolated strong
tstms mainly from 12-15z west of I-95 and 15-18z farther east.
Storm Prediction Center has most of the County Warning Area in a marginal risk for severe, and if a
distinct line or some discrete cells do develop Tue morning,
they will need to be monitored closely. The current pattern
with convection across the deep south and Gulf of Mexico could
be a hint that a split in the precip shield is likely (and thus
most areas should expect only around 0.25" or less of total quantitative precipitation forecast
except for locally higher amounts in tstms and over the far n).
Models remain in good general agreement wrt timing and should
see pops taper off west-east quickly by aftn...W/ pcpn moving out of
the entire area by 21z/Tue to 00z/Wed. With partial aftn
sunshine, deep mixing, and a downslope flow highs Tue will be
breezy and unseasonably warm, possibly close to record highs.
Current forecast is for highs 70-75 f across much of central/southeast
Virginia and NE NC, with 65-70 f on the Eastern Shore and over the
west/northwest sections of the County Warning Area.
Short term /Tuesday night through Thursday/...
dry cooler Tue night/Wed W/ lows mainly in the 30s (around 40 f
se). Mostly sunny with highs Wed upper 40s north and on the ern
shore to 50-55 f elsewhere. Partly cloudy as an upper trough
swings through Wed night with lows in the upper 20s to lower
30s. Mostly sunny cooler/seasonable Thu with highs from the
lower 40s NE to around 50 f south central Virginia.
Long term /Thursday night through Monday/...
overall pattern continues to show the long term period beginning
with a shortwave ridge building eastward from the Mississippi
Valley into the southeastern US and mid-Atlantic states on
Friday into Saturday. This is followed by a full latitude trough
that moves in on Sunday into Monday. But today, the timing
between the models and strength of the cold front crossing the
area is different with the 12z GFS slower and weaker while the
12z European model (ecmwf) is slower, stronger and would provide more rain for
the region. The European model (ecmwf) right now has better run to run continuity
than the GFS as the 6z GFS was slower and wetter than the 12z
run. So for now have leaned a little more toward the slower
European model (ecmwf) for that part of the forecast.
On Thursday night through Friday, high pressure will be in
control of the regions weather with the high overhead expect to
see a very cool night with good radiational cooling, lows in the
m20s-l30s. Temperatures will begin to warm again on Friday as
warm advection begins with SW flow, expect highs in the u40s to
mid 50s. Mex guidance is a bit warmer and began to trend that
direction raising highs a few degrees above the other guidance.
The SW flow continues on Fri night with more dry weather and
maybe a few more clouds. Temperatures in the mid to upper 30s
For Saturday through Sunday night, this is where the most
interesting portion of the extended lies as the quicker GFS has
the moisture and front approaching the area by late Sat
afternoon, which is about 6 to 12 hours faster than the 6z GFS
or European model (ecmwf). At this range, did raise pops a touch, but kept the
forecast dry on Sat with temperatures getting back into the u50s
to l60s. But beginning Sat night did start to raise pops up to
high chance values. Some guidance suggest pops in the likely
range are possible now, but with timing issues and also the
questionable forcing have capped pops at 50% from late Sat night
through Sunday with a slow clearing of the pops in Sunday
evening. Sunday looks like the most probably period for rain and
the European model (ecmwf) would indicate a beneficial rain, which would be good
for the drought areas, but at this range models have been
showing these types of events for the last few weeks, but the
plentiful rain has been materializing. Have kept temps mild on
Sat night and Sunday with lows in the 40s and highs still in the
The front should clear the area Sunday night with northwest and high
pressure building in on Monday. The strength of the developing
upper trough will determine how strong the low over New England
gets Sunday night and this will impact temps on Monday. The
European model (ecmwf) would suggest temperatures cooler than the currently
forecast in the upper 40s to mid 50s on Monday. But for now will
not bit completely on the European model (ecmwf).
Aviation /23z Monday through Saturday/...
tafs begin with VFR conditions at 00z but conditions will
gradually deteriorate during the overnight as clouds and
scattered rain begin to overspread the region. A cold front will
approach from the west late tonight into Tuesday and push off
the coast Tuesday afternoon/evening. The front will be
accompanied by showers and gusty S-SW winds. Cloud ceilings are
expected to diminish to MVFR by Tuesday morning with the chance
for some IFR ceilings and visibilities to occur from near
sunrise through mid afternoon. Instability with the front will
also bring a chance for a few isolated thunderstorms mainly
during the morning and early afternooon. The front pushes off
the coast by mid afternoon into the early evening. High pressure
from the southwest will then build into the region for
high pressure over the waters is shifting east and offshore this
evening as low pressure moves into the Great Lakes. A
tightening pres gradient ahead of the approaching cold front
tonight will increase winds to 15 to 25 kt from the S-SW prior
to daybreak tues. These winds will persist thru midday/early
aftn Tue becoming rather gusty by mid morning. Seas on the
coastal waters building to 4-6 ft; waves 3-4 ft on the Bay
rather quickly in response to the SW winds. Scas remain in
effect for all waters overnight into Tuesday. With the primary
surface low so far displaced to the north it will be hard to get
gales with warm S-SW winds over cold water this time of year,
but did keep mention of a few gusts to 30 to 35 kt for our
northern coastal waters.
Once the front clears the area tues afternoon, winds will shift
to the west 15 kt tues night/Wed and then northwest on Thursday.
Waves/seas subside to 2-3 ft. There is another surge of cold
air Wed night into early Thu which will maintain the northwest winds
of 15 kt with some higher gusts. Waves and seas may increase by
a foot to 2 to 4 ft with this surge Thu. Conditions improve by
Friday as weak high pressure builds into the area.
record high temperatures today and Tuesday.
ric 75/1906 76/1974
orf 77/1937 76/1999
sby 72/1927 73/1999
ecg 79/1937 76/1937
Marine...Small Craft Advisory from 4 am to 6 PM EST Tuesday for
Small Craft Advisory from 6 am to 6 PM EST Tuesday for anz633.
Small Craft Advisory from 4 am Tuesday to midnight EST Tuesday
night for anz650-652-654.
Small Craft Advisory from 6 am to 10 PM EST Tuesday for anz656-