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fxus61 kakq 210135 
afdakq

Area forecast discussion
National Weather Service Wakefield Virginia
935 PM EDT Thu Jul 20 2017

Synopsis...
high pressure builds toward the mid Atlantic today into the
weekend, bringing increasingly hot and humid conditions to the
area. The hottest weather can be expected from Friday through
Sunday.

&&

Near term /through Friday/...
current analysis indicates a weak sfc/Lee trough of low
pressure located from New Jersey...south-southwest to south central Virginia and central
NC. The trough of low pressure aloft is now situated south of
the County Warning Area and centered along the SC/Georgia coast. The sky is partly
cloudy this evening under thin cirrus with some patches of
8-12kft altocu. Very warm and humid this evening with
temperatures ranging from the upper 70s to mid 80s. A few
isolated showers/tstms from earlier have now dissipated. Mainly
dry overnight. Earlier convection over Ohio/in has weakened and
seems unlikely to hold together as a weak wave aloft crosses north
of the area overnight in the west-northwest aloft. Warmer than last night
with lows staying 70-75 f or higher tonight.

Model consensus has the upper ridge axis centered from the Tennessee
Valley to NC on Fri into early Sat, with an upper trough over
the eastern Great Lakes and NE states. The core of the highest
850 temperatures on Fri (21-22c) will be over much of the local
area of Fri and with dew pts expected to be higher (only mixing
out to around 70 f inland and to the lower-mid 70s near the
coast). Expect heat indices to be more solidly into advisory
criteria (105 to 109 f) and have therefore issued a heat
advisory for most of the County Warning Area (left coastal Worcester/NC Outer
Banks out for now with cooler temperatures as well as much of
the far SW where it will be slightly drier). Actual highs will
be around 100 f Metro Richmond to the mid/upper 90s elsewhere
(locally cooler/lower 90s immediate coast). As far as precip
chances, airmass appears too stable overall for much in the way
of pop-up storms during the day, but with west-northwest flow aloft and
some weak shortwave energy moving into the area by late aftn,
will have ~20% pops by mid/late aftn over the northwest 1/2 of the County Warning Area.
Enough shear moves into the far northwest for a marginal risk for
severe with wind being the main threat is any type of convective
complex can hold together upon crossing the mtns.

&&

Short term /Friday night through Sunday/...
ramped pops up a bit more for Fri night/especially north/NE zones
closest to upper level shortwave energy tracking through the west-northwest
flow aloft. Very warm/humid Fri night with lows mainly 75 to 80
f. Slightly cooler most areas for Sat due to potential for more
clouds and as core of 850 mb heat shifts a bit S. However, it
will be even more humid so expect at least southern portions of
the County Warning Area to need a heat advisory even with highs on avg only in
the mid 90s. As airmass destabilizes more by Sat aftn/early
evening, and as heights aloft drop, convection developing from
the northwest will be more likely to hold together for at least 30-50%
pops across most areas (20% NE nc) from late Sat aftn through
Sat night. Far north/NE portions of the County Warning Area are in a slight risk
where higher shear will reside with marginal risk for the
remainder of the County Warning Area. Again wind will be the primary threat.
Lows mainly in the mid to upper 70s Sat night and continued hot
an humid with additional heat headlines likely needed for some
of the region on Sunday. Highs mainly in the mid to upper 90s
Sunday.

&&

Long term /Sunday night through Thursday/...
long term period will feature near normal temps on avg and
occasional chances for rain. In general expect lwr temps than this
weekend as the broad upr-level ridge across the eastern Continental U.S. Breaks
down in response to an approaching upr-level trough. The trough and
associated low-level front will bring an increasing chance for rain
Mon, but will cap pops at 40% for now due to uncertainties regarding
timing and available moisture. Further model divergence occurs Tue
and Wed, with the 12z European model (ecmwf) keeping the low-level boundary in the
vicinity and the 12z GFS pushing things offshore, so will maintain
low end pops (20-40%) through midweek, with the best chance over far
southeast areas. As for temps, after one more hot day Mon with highs up to
the mid 90s, expect mid/upr 80s for Tue through Thu.

&&

Aviation /02z Friday through Tuesday/...
high pressure will prevail off the southeast coast tonight into
Friday, with a trough to the Lee of the Appalachians. This will
promote light SW flow of 5-10kt. Thin high clouds tonight, with
sct aftn cu Friday. Mainly dry with only a minimal chc (15-20%)
of showers/tstms Friday aftn/evening. Similar conditions persist
into Saturday with a 20-40% chc (highest n) of late aftn/evening
showers tstms. A low probability of late aftn/evening
showers/tstms continues Sunday/Monday, but overall primarily
dry. A weak cold front approaches from the northwest Tuesday.

&&

Marine...
extended period of sub-Small Craft Advisory conditions continues this week into the
weekend. Pattern is stagnant with Bermuda high pres centered well
offshore and typical summertime late day thermal troughs with S/SW
winds averaging 5-10 kt, occasionally up to 15 kt especially tonight
due to a slight increase in the pressure gradient. Waves over the
Bay 1-2 ft with seas over coastal wtrs 2-3 ft. The next (weakening)
cold front approaches the region late Mon, dropping into the area
Mon night/Tue. Mainly sub-Small Craft Advisory conditions expected to continue
however with weak cold air advection behind the front, and just some 4-5 ft seas
psbl out 20 nm. Flow becomes north/nely then Tue through Thu as the frnt
slides offshore and dissipates.

&&

Climate...
heatwave is expected to develop, mainly Friday through Sunday.
The 2nd half of July is climatologically the hottest few weeks
of the year so we still may not set any daily records at our
main climate sites. For reference, record highs today through
Sunday are listed below:

* date: today(7/20) fri(7/21) sat(7/22) sun(7/23)

* ric: 103/1930 104/1930 103/1952 103/1952
* orf: 102/1942 101/1926 102/2011 103/2011
* sby: 104/1930 106/1930 104/1930 103/2011
* ecg: 104/1942 102/1987 104/1952 104/1952

&&

Akq watches/warnings/advisories...
Maryland...heat advisory from 10 am to 8 PM EDT Friday for mdz021>024.
NC...heat advisory from 10 am to 8 PM EDT Friday for ncz012>017-
030>032.
Virginia...heat advisory from 10 am to 8 PM EDT Friday for vaz048-061-062-
064-068-069-075>078-080>090-092-093-095>100-509>525.
Marine...none.

&&

$$
Synopsis...lkb/tmg
near term...lkb/ajz
short term...lkb/tmg

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