Scientific Forecaster Discussion
fxus61 kakq 171951
Area forecast discussion
National Weather Service Wakefield Virginia
351 PM EDT Wed Jul 17 2019
high pressure remains off the southeast coast through the weekend.
A trough of low pressure will cross the region tonight and Thursday.
Otherwise, hot and humid weather will continue until Monday.
Near term /until 6 am Thursday morning/...
as of 330 PM EDT Wednesday...
Latest msas has the sfc high over the sern states with a sfc trof
east of the mts. Scattered convection has developed across the
sern zones on leftover boundaries along with storms firing up
along the Lee trof. Temp wise, heat index values btwn 105-110
over the east with dew points btwn 75-80 while gusty west winds
has mixed out the column a bit as dew points has dropped to btwn
65-70 over the Piedmont.
Models show the sern convection waning this eve while convection
continues to move east along the Lee trof. Thus, will have chc pops
this eve most areas, tapering off across the west after midnite but
continuing along the coast thru the overnite hrs. Warm and muggy
with lows in the 70s to near 80 ivof Hampton Roads.
Short term /6 am Thursday morning through Saturday night/...
as of 330 PM EDT Wednesday...
Sfc trof progged to linger over the area thurs. This continues the
threat for scattered convection, with the models showing more
coverage across the entire local during the aftrn. Temps will
quickly rise into the 90s once again, but expect the added cloud
coverage and dvlpng pcpn to limit highs into the low-mid 90s.
Tricky part of the forecast will be the dew points as per todays
readings near 80 ivof the warm waters of the Currituck Sound
and rivers of nern NC. Given this, and the fact that little if
any cooling occurs across the se tonite, decided to extend the
heat advsry for both tonite thru thurs aftrn across sern Virginia/ NE
NC. Otw, expect the dvlpng convection thurs to limit the heat
index values to arnd 100.
Convection ends across the west thurs eve but lingers along the
coast thru the nite as the trof slowly drifts towards the coast.
Lows in the 70s.
High pressure (both at the sfc and aloft) build from the sern states
west into the mid MS valley this weekend. 850 mb temps btwn 20-22c will
result a capped airmass suppressing convection from firing up both
Fri and Sat. This breaks down a bit sun with some late day storms
possible across the Piedmont. The concern will be for extreme heat
(highest since 2012) arnd these parts. Combo of high temps mid-upr
90s and dew points in the mid-upr 70s yields heat index values 105-
110 Fri (heat advisory levels). The heat peaks Sat/sun with highs
upr 90s-lwr 100s and heat index values aoa 110 (excessive heat
warning levels). Will continue to highlight this potential in the
severe weather potential statement. Record highs may be tough to reach but record high lows appear
attainable...see climate below.
Long term /Sunday through Wednesday/...
as of 240 PM EDT Tuesday...
The GFS and European model (ecmwf) continue to advertise a developing eastern US
trough and a weakening of the Bermuda high for early next week,
although the trend is a little slower than yesterday. This results
in a break in the heat wave after Monday and also with the cold
front likely to stall either along the coast or in the Carolinas,
expect a chance for showers and storms to continue through midweek,
especially along southeast portions of Virginia and NE NC. The 12z GFS seems
climatologically to be too strong in trying to develop a closed low
over the Tennessee/Alabama by midweek. At this point perfer more of the European model (ecmwf)
solution with the NE trough being maintained farther to the north
with just a weakness lingering between the ridges over the lower MS
valley. This would be drier solution for the area for Wednesday into
the later portion of next week.
At this point have held to chance pops each day with the best chance
for rain with the frontal passage from late Monday through Tuesday
evening. Temperatures will continue to be very warm on Monday with
highs in the low to mid 90s, followed by a drop off into the mid to
upper 80s on Tuesday on Wednesday with the front moving through and
an increase in clouds.
Aviation /20z Wednesday through Monday/...
as of 200 PM EDT Wednesday...
VFR conditions expected through most of the forecast period.
Exception will be for sct convection this aftrn ivof ecg and
after 21z at ric. Although ceilings may drop to MVFR, visibilities may
briefly drop to below 3sm in locally hvy downpours. Thus, went
with a thunderstorms in the vicinity at both sites for now. Some guid hinting at addntl
convection moving east across towards coastal sites after 03z
as a sfc trof moves across the region.
Outlook: models show a better chc for more widespread convection
Thu as the sfc trof lingers across the area. Otw, VFR conditons
expected thru the weekend as the sern high dominates.
as of 330 PM EDT Wednesday...
This afternoon SW winds of 10 to 15 kt were in response to the
trough oriented over the Piedmont and high pressure well
offshore. Expect some widely scattered storm activity mainly
over the Lower Bay and coastal waters from Cape Charles south
this late afternoon and evening, though there should not be as
much storm activity as yesterday. More showers and storms may
push into the Bay and coastal waters from the west late this
evening after 8 PM as a weak upper trough moves through. Given
the heat even tonight, expect that any storm could produce
winds gusts of 25 kt or greater.
Overnight SW winds will increase as the trough approaches
tightening the pressure gradient a bit. South-southwest winds increase to 15
kt with some gusts to 20 kt over ches Bay, and 15 to 20 kt in
the coastal waters. This will build waves to 2 ft in the Bay,
and seas to 3-4 ft on the coastal waters. Have raised a Small Craft Advisory in
the Bay for wind gusts to 20 kt late this evening and tonight.
The winds will begin to relax to 10 kt on the Bay and rivers,
and 10 to 15 kt on the ocean waters Thu morning, as the trough
of low pressure stalls. Expect more storm activity on Thursday
with more of a potential for convective wind gusts for 30 kt or
greater Thu afternoon and evening.
This pattern will continue into Fri, allowing for a continued
weakening of the winds to 5-10 kt. But, once the weak trough
breaks down, the Bermuda high will once again begin to build
into the region and south-southwest flow will again strengthen to 10-15 kt
over most of the waters for Fri night thru sun.
upcoming heatwave may challenge or break record highs and/or
record high lows (esp from Fri through sun).
Richmond record high record high low
Fri (7/19) 101/194277/2013
Mon (7/22) 103/195279/2011
Norfolkrecord highrecord high low
Fri (7/19) 101/194284/1942
Mon (7/22) 102/201182/2011
Salisburyrecord highrecord high low
Wed (7/17) 99/201280/1983
Fri (7/19) 99/197778/2013
Mon (7/22) 104/193080/2011
Elizabeth cityrecord highrecord high low
Wed (7/17) 99/194278/1995
Fri (7/19) 105/194280/2012
Mon (7/22) 104/195279/2011
Maryland...heat advisory until 8 PM EDT this evening for mdz021>024.
NC...heat advisory until 8 PM EDT this evening for ncz012.
Heat advisory until 7 PM EDT Thursday for ncz013>017-030>032.
Virginia...heat advisory until 8 PM EDT this evening for vaz064-075>090-
Heat advisory until 7 PM EDT Thursday for vaz095>098.
Marine...Small Craft Advisory from 7 PM this evening to 7 am EDT
Thursday for anz630>632-634.