Scientific Forecaster Discussion
fxus61 kakq 202126
Area forecast discussion
National Weather Service Wakefield Virginia
426 PM EST Sat Jan 20 2018
high pressure slides off the southeast coast through the
weekend. A cold front crosses the region Tuesday morning.
Near term /until 6 am Sunday morning/...
latest surface analysis features a ridge of high pressure the
southeast. Aloft, a weakening shortwave continues to push across
the Gulf Coast this afternoon...with flat, quasi-zonal flow in
between this feature and a northern shortwave moving across S
qc. Meanwhile to the west, a strong shortwave is pushing east
across the desert SW toward the southern rockies.
Dry, mild flow aloft and light SW winds at the sfc have allowed
for another mild afternoon across the local area. High
temperatures across the area generally in the lower 60s
inland...to the m50s to around 60f over the Eastern Shore.
Upper trough over the southeast slides offshore late tonight. Clear sky
and light winds will allow temperatures to drop off quickly this
evening. Potential for patchy fog after 06z late tonight/early
sun. Early morning lows mainly in the 30s, with some upper 20s
possible in the Piedmont.
Short term /6 am Sunday morning through Tuesday/...
short term period generally characterized by dry and gradually
warming temperatures. Upper level trough out west will gradually
deepen/close off as it lifts onto the plains Sunday...and to the
mid-Mississippi Valley on Monday. At the surface, SW flow
continues as the surface ridge slowly lifts over the local area.
Upper low and associated sfc low lifts across the western Great
Lakes, with the attendant cold front crossing the area late Mon
night into Tuesday. European model (ecmwf)/GFS blend still nicely captures the
slower European model (ecmwf) and the more progressive GFS. Highs Sunday similar
to today...mainly u50s to l60s inland...55 to 60 along the
Eastern Shore. Highs Monday will be a challenge, and partially
dependent on clearing low clouds out to begin the day. Highs
expected to be in the l-M 60s inland. However, if clearing
occurs a bit quicker than modeled, thickness tools and some
gefs/eps members pointing at potential highs in the u60s to
near 70 inland. Lows Monday night remain mild ahead of the
front...mainly in the 50s.
Rain chances increase quickly after midnight Monday night/Tuesday
morning. Sherb/sherbe (qlcs) parameters continue to point
towards potential for another round of sct thunderstorms, or
some gusty line segments Monday night. For now, given 06-15z
timing will keep thunder mention out. Showers do lift out by
midday Tuesday out west, early evening along the coast. Highs
Tuesday in the 60s once again, slightly cooler 50s out in the
Long term /Tuesday night through Saturday/...
models are in very good agreement in the extended range from 00z
Wed through Saturday with the long wave trough pulling out of
the northeastern US Wed and Thursday with a shortwave ridge
building in for Friday and Saturday. At the surface, the period
begins with northwest flow as the surface low over deepens over the
nern US. The surface low will lift NE into the Canadian
Maritimes by Wed evening. With the northwest flow, expect the clouds
to clear tues night into Wednesday but with the cold advection,
temperatures will be cooler into the upper 40s to lower 50s.
Another shortwave will move through the eastern trough on
Tuesday and will bring a reinforcing cold front to the area.
This will knock temperatures down a couple more degrees on
Thursday, but with little moisture expect to see just a few
clouds across the northern portion of the County Warning Area.
High pressure will build into the area on Thursday night into
Friday. The high will remain in place through Saturday before
slowly sliding off the coast by late Saturday with SW flow
returning. This will allow for good radiation cooling both thurs
and Fri night with temps in the u 20s to l30s thurs night and
low to mid 30s Friday night. For Friday should see lots of sun
with highs around the mid 40s over lower Maryland and near 50 in
southern Virginia. On Saturday with the return flow the models are
indicating return moisture getting in and some showers possible
late day, but at this point, not ready to introduce pops so have
gone with just slight chance values in the 15 to 20% range.
High should continue to modify into the low to mid 50s.
Aviation /21z Saturday through Thursday/...
VFR conditions continue through the 18z taf period as sfc hi
pres to the S dominates. Light SW wind ~10 kts through this
evening becoming light overnight. Some scattered-broken stratus develops
this evening across the Piedmont, but should mix out quickly
after sunrise Sun morning.
Outlook: sfc hi pres settles off the southeast coast sun and Mon W/
sky clear and dry conditions continuing. Another night of low
clouds/patchy fog possible Monday morning. Otherwise, the next
chance for widespread precipitation and flight restrictions
comes Monday night with a passing cold front. High pres returns
high pressure, centered just off the southeast US coast will
remain in control of the regions weather tonight into Monday
with generally light winds and generally benign conditions on
the waters. The winds will gradually increase Sunday afternoon
into Monday from the SW, but will remain well below Small Craft Advisory levels
through Monday evening. By Monday night, the flow will begin to
increase again out of the south as a deepening low over the
Great Lakes and it associated cold front impact the region. The
winds will increase from to around 20 to 25 kt with seas on the
coastal waters increasing to around 4 to 6 feet. Once the front
clears during the day on Tuesday, the winds will shift to the
west and then northwest on Wed and Thursday, as a secondary
surge of cold air moves through. Conditions will be close to Small Craft Advisory
levels in the northwest flow as cold advection develops and allow for
more mixing which keeps the wind up. High pressure slides over
the area with benign conditions for the end of the week.