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Area Forecast Discussion (AFD)

Issued by Baltimore/Washington (LWX)

FXUS61 KLWX 180805

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
405 AM EDT Mon Jun 18 2018

High pressure will remain off of the Mid-Atlantic coast today. 
A cold front will approach the area from the north on Tuesday 
and stall across the area during the middle of the week. The
front may push south of the area by Friday before lifting back
north over the weekend.


High pressure is located offshore this morning with a large upper 
level ridge encompassing the southeastern CONUS. Cirrus clouds may 
be inhibiting fog development to an extent, but it is showing up in 
patches. Isolated dense fog is possible, mainly in the rural river 

The main story for today is the heat. Feel comfortable with the 
forecast of highs in the lower to mid 90s and dew points in the 
upper 60s to lower 70s this afternoon. That puts dew points in the 
upper 90s to low 100s. Didn't feel confident to put any particular 
area in a Heat Advisory based on criteria, though it will come 
close. Convective development is mainly limited to the CAMs, but 
there may be a subtle lee trough which could spark a few showers and 
storms. Most areas will remain dry though.

A cold front will be approaching from the north tonight. The NAM 
displays the quick end of possibilities, with showers and storms 
pushing into northern Maryland after midnight. Have sided with the 
consensus for the forecast, leaving low chances of precipitation for 
late tonight. In southern parts of the CWA where it will remain 
clearer, some patchy fog will be possible again. Lows will be in the 
70s to around 80.


The front will continue southward on Tuesday, taking on a bit of a 
backdoor orientation and stalling out, as troughing moves off the 
New England coast while ridging remains prominent in the Mississippi 
Valley. Thunderstorms will likely develop along the front Tuesday 
afternoon, and with the mid/upper flow parallel to the boundary and 
a deep warm cloud layer, locally heavy rain will be the main threat. 
Heat indices may top 100 again south of the front (north central 
VA), while highs will remain in the lower to mid 80s to the north.

The front may push a bit to the south Tuesday night but lift back to 
the north on Wednesday as a wave of low pressure tracks along it. 
It's tough to rule out precipitation at any point through this 
stretch, although diurnal instability will increase the odds. In 
addition to the locally heavy rain threat again on Wednesday, deep 
shear will increase into the 25-35 kt range ahead of a mid level 
impulse, which means a few severe storms will be possible as well. 
Temperatures will continue to be modulated by the frontal position 
and cloud cover.


A front will be over our area on Thursday, keeping the chance 
of showers and thunderstorms over our region. Guidance is coming
into somewhat better agreement on the position of this front 
Thursday night into Friday. Now the determinist ECMWF has joined
the GFS by pushing the front south our area Thursday night into
Friday, but how far south is still questionable. This solution 
brings drier air into our parts of our CWA as surface high 
pressure builds over our from the north. This high pressure will
then move offshore later on Friday. The front to our south will
lift north as a warm front on Saturday as a low pressure tracks
from the Mid-West into the Great Lakes. A cold front associated
to this low will then approach on Sunday and be near/over us on

High temperatures during this period will be in the low to mid 80s, 
with some 70s at higher elevations.


Patchy fog is developing early this morning. Brief IFR can't be 
ruled out, with the best chance at MRB. VFR is expected for the 
remainder of the day. An isolated storm could develop near the Blue 
Ridge, but the chance of one impacting a terminal is too low to 
include in the TAFs.

A cold front will push toward the area late tonight into Tuesday. 
Some patchy fog is possible tonight if clouds hold off. The chance 
of showers and storms will increase Tuesday afternoon. Some low 
clouds could occur along the front as well. The front will stall 
nearby through Wednesday. Precipitation could occur at any time, 
though the highest chances will mainly be in the afternoon. Low 
clouds could develop Wednesday morning if the front pushes far 
enough to the south.

A frontal boundary is expected to be over our area on Thursday.
The front is forecast to push south on Friday, and then lift 
north as a warm front on Saturday. Periods of showers and 
thunderstorms are possible during this period causing sub-VFR 
conditions over some terminals.


Expecting winds to remain below SCA criteria through tonight. A bit 
of uncertainty on Tuesday as a cold front drops south into the area, 
but for the most part am expecting winds to be less than 15 kt. The 
front will stall across the area through Wednesday, so winds should 
be light, but there will be chances for thunderstorms at times, 
especially south of the front.

A frontal boundary is expected to be over our area on Thursday.
The front is forecast to push south on Friday, and then lift 
north as a warm front on Saturday. Periods of showers and 
thunderstorms are possible during this period. Winds gusts are 
expected to remain below the small craft advisory criteria, 
therefore not anticipating an advisory during this period. 


Well above normal temperatures are forecast today through 
Tuesday. Below is a list of daily record warm temperatures.

Washington DC area (DCA)
Date      Record High      Record Warm Low
June 17   97 (2014)        76 (1952, 1939)
June 18   97 (1944)        77 (2014, 1957)
June 19   99 (1994)        75 (2011, 1994, 1981, 1978)
Temperature records for the Washington DC area have been kept 
at Ronald Reagan Washington National Airport since 1945. 
Additional temperature records observed downtown date back to 

Baltimore MD area (BWI)
Date      Record High      Record Warm Low
June 17   96 (1939)        76 (1913)
June 18   97 (1957, 1944)  75 (1957)
June 19   99 (1994)        74 (1905)
Temperature records for the Baltimore MD area have been kept 
at Baltimore-Washington International Thurgood Marshall 
Airport since 1950. Additional temperature records observed 
downtown date back to 1872.

Dulles VA area (IAD)
Date      Record High      Record Warm Low
June 17   92 (1994)        72 (1996)
June 18   94 (2007, 2006)  73 (2017)
June 19   98 (1994)        71 (2014)
Temperature records for the Dulles VA area have been kept at 
Washington Dulles International Airport since 1960.