Severe Thunderstorm Warning 299, NWS Baltimore/Washington

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
236 PM EDT Wed Sep 7 2016

.SYNOPSIS...

The Mid Atlantic remains between low pressure south of Long
Island and high pressure to the southwest. The low will eventually
move to the northeast late in the week as a weak boundary sets up
near the region to start the weekend. A cold front will swing
through the area Sunday. High pressure will build into the region
in its wake.

&&

.NEAR TERM /THROUGH TONIGHT/...

Convection is beginning to develop along the boundary stretching
across central PA. As discussed this morning the steering flow is
from the north at about 30 knots. This single fact is going to
keep the flood threat on the low end. If a storm were to grow tall
enough though the additional forward wind speed would be added
onto any storm-generated downburst. This will need to be watched
as well as storm which look like they could move over the Bay/
Potomac.

Convection should diminish after mid evening. This could play
havoc with the low temperature forecast - if one place gets rain
temperatures may drop several degrees lower than expected. Overall
a "sultry" September night - not a term I normally use after
August. Lows in the cities are expected to be in the mid
70s...65-70 elsewhere. See the climate section below - max low
temperature records are in jeopardy.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...

The big story Thursday will be the temperatures of 10+ degrees
above normal. This will lead to afternoon highs in the mid 90s
across much of the area with heat index values around 100.

Warm temperatures are expected to persist Thursday night and
Friday. Friday has the better chance of convection..although
better chances will exist this weekend.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...

Weakening boundary over our CWA will allow for a drying conditions
Friday night into early Saturday. Approaching cold front from the
west will be increasing PoPs from west to east Saturday. Guidance
suggests the front will move across our CWA early Sunday. High
pressure then builds in from the west behind the front through
Wednesday. Another front approaches the CWA late Wednesday.

Saturday looks like the warmest day of the period, with high
temperatures in the low to mid 90s, and heat indexes in the upper
90s. High temperatures for the rest of the period is in the mid 80s.

&&

.AVIATION /17Z WEDNESDAY THROUGH SUNDAY/...

VFR conditions expected for the remainder of today/tonight. If
showers/thunderstorms develop near airports brief degredations can
be expected...as well as the possbility of late night/early
morning fog.

VFR conditions expected Thursday-Friday.

Mainly VFR conditions expected Friday night into Monday.
Scattered showers and thunderstorms possible Friday night and
Saturday causing sub-VFR conditions.

&&

.MARINE...

Sub SCA conditions expected on the waters through Friday. Today's
concern will be if any cells get close enough to the waters to
warrant SMW's being issued.

Small Craft Advisory conditions possible Saturday night into
Sunday morning. Some showers and thunderstorms possible Friday
night and into Saturday. Small Craft Advisory conditions not
expected for Sunday into Monday.

&&

.TIDES/COASTAL FLOODING...

With diurnal increase in N/NW flow, water levels are easing a bit
but still 1.3-1.5 ft above normal. With the combination of light
winds and stagnant low pressure offshore, am not foreseeing a large
decrease in water levels through tonight. Coastal flood advisories
are already out for one more high tide cycle except for Havre de
Grace, which will need to be monitored. Even though the evening high
tide is higher astronomically, moderate flood levels do not appear
to be threatened at this time.

ESTOFS shows a quicker decrease in water levels Thursday, eventually
reaching similar surge numbers to the ETSS by Friday morning. Thus
this part of the forecast remains uncertain. Am doubting we see a
complete return to normal until a cold front passes late in the
weekend, meaning minor coastal flooding will at least need to be
monitored until then.

&&

.CLIMATE...

Here are record daily high and record daily high minimum
temperatures for the next several days.

In the tables below, underneath the name of the site, the first
row is the date, the second row is the record daily high, and the
third row is the record daily high minimum.

' denotes record highest for the month of September
* denotes record also occurred in previous years; most recent
  occurrence listed

Washington DC area (Reagan National Airport, DCA)
  09/07       09/08       09/09       09/10       09/11
104 (1881)' 100 (1939)  98 (1872)   98 (1983)   98 (1983)
 76 (1985)*  76 (1985)  75 (2015)*  75 (1947)   76 (2013)
(Records at airport since 1941, in DC area since 1872)

Baltimore MD area (Baltimore-Washington International Thurgood
Marshall Airport, BWI)
  09/07       09/08       09/09       09/10       09/11
101 (1881)' 100 (1939)  94 (2015)*  98 (1983)   100 (1983)
 75 (1900)   77 (1881)  75 (1884)   76 (1915)    78 (1931)
(Records at airport since 1950, in Baltimore area since 1870)

Dulles International Airport VA (IAD)
  09/07       09/08       09/09       09/10       09/11
 95 (1985)*  93 (2015)*  95 (1985)   99 (1983)'  99 (1983)'
 70 (2007)   72 (2004)   72 (2015)   71 (2007)   72 (1971)*
(Records at airport since 1962)

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 5 AM EDT Thursday for DCZ001.
MD...Coastal Flood Advisory until midnight EDT tonight for MDZ017-
     018.
     Coastal Flood Advisory until 5 AM EDT Thursday for MDZ011-014.
VA...Coastal Flood Advisory until 5 AM EDT Thursday for VAZ054.
WV...None.
MARINE...None.

&&

PRODUCTS...WOODY!/ADS/IFR/DFH

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>