-- Discussion containing changed information from previous version are highlighted. --
683
FXUS61 KLWX 170130
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
930 PM EDT Sun Jun 16 2024

.SYNOPSIS...
High pressure over New England will drift offshore through the week.
A warm front over the Tennessee River Valley will lift northeastward
across the Mid-Atlantic through Monday, marking the beginning of a
prolonged period of heat.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
A surface warm front is analyzed across the Tennessee Valley
this evening, which will quickly lift to the north of the area
by Monday morning. With ridging aloft centered south of the
area, warm and moist advection has already commenced, with
several areas of broken cloud cover noted across the region.
Overall, the night will average partly cloudy, and it will be
warmer and more humid than last night. Lows will be in the 60s
for most of the area, and around 70 in the urban centers and
along the water. Some guidance indicates showers may form along
the Appalachians around sunrise in response to the warm front.
Most areas will likely remain dry.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
For the start of the work week, a strong ridge aloft will become
the main story for our region. The aforementioned warm front
should be north of our region on Monday, resulting in noticeably
warmer high temperatures as well as a more humid air mass as
well.

Given the increase in heat and humidity, and prior to the ridge
aloft and associated subsidence increasing heading into
midweek, there may be enough of a window for scattered showers
and thunderstorms west of the Blue Ridge Mountains as a lee
trough develops thanks to differential heating affects of the
higher terrain. Flow will be modest in the mid and upper levels
and light in the low levels, so heavy downpours and localized
gusty winds would be the main threats with any stronger
storms. Model guidance seems to have a consensus of around
1500-2500 J/kg of CAPE available in the aforementioned region.
The one caveat is the presence of mid-level westerlies, which
could squash most activity that tries to develop. Given the
increase in heat and humidity and slow/chaotic storm motions in
the vicinity of the terrain, some isolated heavy rain totals
can`t be ruled out. Depending on mesoscale evolution, some cells
could drift into the central Shenandoah Valley toward evening.
Otherwise, most of the time/area will be dry.

High temperatures tomorrow have decreased a bit in recent
forecasts, with a noticeable trend of the worst of the heat
being towards the end of the week. Latest forecast calls for
highs in the low-mid 90s, with heat indices generally between
95-100 degrees. For folks west of the Blue Ridge however, we
will have to see how thunderstorms may impact those highs.

There is some increasing threat for a thunderstorm threat again
on Tuesday in the same area, but amidst the building ridge
aloft, the thinking is that coverage should certainly be less
than what we see Monday. However, temperatures will trend
hotter Tuesday as highs are expected to reach the mid 90s.
Humidity may also be higher Tuesday, though guidance is still
struggling with that aspect of the forecast.

In the short term, given the uncertainty, and the very threshold
nature of this event with regards to local heat advisory criteria,
have decided to hold off for now. Thinking the best chance
early in the week may be Tuesday afternoon for areas west of the
Blue Ridge, where criteria is 100F heat index. Areas further
east though, where criteria is 105F heat index, we may not quite
reach that.

It is important to note however that this level of heat is
still dangerous and should not be taken lightly. This will be an
extended period of very warm temperatures, likely peaking
towards the end of this week into this weekend. We encourage all
to follow all heat precautions in the coming week. Stay cool,
stay hydrated, and take plenty of breaks if you must work
outdoors.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A broad upper level ridge will remain in place over our region with
high pressure over much of the mid-Atlantic through the end of this
week. An extended period of 90 degree plus temperatures is likely to
continue through Saturday with potential for near record
temperatures possible. The early season nature of this extended
period of 90 degree plus weather combined with increasing heat
indices that could peak between 100 and 105 will likely necessitate
the need for some heat headlines by the end of this week into
the weekend. Showers and thunderstorms are not expected at this
time Wednesday into Thursday as the ridge should keep
convection to the north over PA. Showers and thunderstorms will
become increasingly possible late Friday and through the
weekend.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --
VFR conditions are likely at the terminals through the next
several days. An isolated thunderstorm can`t be ruled out
Monday or Tuesday afternoon near MRB and CHO, but confidence is
too low to include in the TAF at this time. Not seeing a chance
for that activity to make it east into the metro area at this
time. Winds during this period will generally be out of the S/SE
around 6 to 12 knots during with occasional gusts to around 18
knots during the afternoons. Bay/river breeze wind shifts will
likely continue to affect DCA/BWI/MTN daily.

VFR conditions are likely Wednesday through Saturday with winds
generally out of the south.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
Winds are generally going to be out of the south or southeast through
the middle of the week. With a warm front passing tonight into
Monday, gusty winds are forecast to be a little more widespread
and of longer duration. Some timing adjustments and expansions
have taken place with the Small Craft Advisories. Looking beyond
Monday evening, the pattern will be very similar each day, with
stronger winds picking up each afternoon/evening in southerly
channeling. Thinking that SCAs will be needed most late
afternoons and evenings during this timeframe over the
Chesapeake Bay zones.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
-- Changed Discussion --
A persistent southerly flow will lead to increased anomalies and
some elevated tidal cycles. A few tidal sites will reach action
stage with near minor tidal flooding possible, especially at
Annapolis.
-- End Changed Discussion --

&&

.CLIMATE...
While hot temperatures are expected much of this coming week and
especially this coming weekend, trends have been down early in
the week overall. We could see a few records broken on Tuesday,
but the hottest days appear to be Friday and Saturday, where
several records come be in jeopardy. Below is a list of record
high temperatures for June 18th, 21st, and 22nd, the year the
record was set, and the current forecast high temperatures for
those days. RERs are currently only issued for DCA, IAD, BWI,
and MRB, but other sites are shown for reference.

                                     Tuesday Jun 18th
Climate Site                  Record High     Forecast High
Washington-National (DCA)     97F (1944)          94F
Washington-Dulles (IAD)       94F (2018+)         94F
Baltimore (BWI)               97F (1957+)         92F
Martinsburg (MRB)             99F (1943)          93F
Charlottesville (CHO)         96F (2014+)         93F
Annapolis (NAK)               96F (1957)          87F
Hagerstown (HGR)              95F (1957)          95F

                                     Friday Jun 21st
Climate Site                  Record High     Forecast High
Washington-National (DCA)     99F (2012)          98F
Washington-Dulles (IAD)       98F (1988)          98F
Baltimore (BWI)              100F (2012+)         96F
Martinsburg (MRB)            102F (1931)          95F
Charlottesville (CHO)         99F (1933)          97F
Annapolis (NAK)              100F (1988)          91F
Hagerstown (HGR)              97F (1923)          97F

                                    Saturday Jun 22nd
Climate Site                  Record High     Forecast High
Washington-National (DCA)    101F (1988)          100F
Washington-Dulles (IAD)       99F (1988)          100F
Baltimore (BWI)              100F (1988)          98F
Martinsburg (MRB)            102F (1933)          97F
Charlottesville (CHO)        101F (1933)          99F
Annapolis (NAK)              101F (1988)          94F
Hagerstown (HGR)             100F (1988)          99F

+ indicates that value has been reached on multiple years, with
the year displayed being the most recent.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 2 AM EDT Monday for ANZ530-536-539-
     542.
     Small Craft Advisory from 10 AM to 9 PM EDT Monday for ANZ530-
     538-539-542.
     Small Craft Advisory until 2 AM EDT Tuesday for ANZ531>534-537-
     540-541-543.
-- End Changed Discussion --

&&

$$

SYNOPSIS...CJL
NEAR TERM...ADS
SHORT TERM...CJL
LONG TERM...JMG
AVIATION...ADS/CJL/JMG
MARINE...ADS/CJL/JMG
TIDES/COASTAL FLOODING...JMG
CLIMATE...CJL