Area Forecast Discussion

FXUS61 KLWX 240751
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
351 AM EDT Mon Jun 24 2019
A warm front will lift north through the region today, with a 
weak cold front also approaching from the west. The cold front 
pushes through Tuesday, but will be very weak, likely having no 
cooling effect on temperatures. Hot and humid through the end of
the week, as high pressure builds in from the Tennessee Valley,
eventually moving offshore late this week into the weekend. 
Next frontal system could push through this weekend.
A previously stationary frontal boundary, positioned well to our
southwest over the past few days, has begun to lift northward,
and will continue to slowly do so throughout the day. Overrunning
moisture associated with this front could lead to some spotty 
showers this morning, primarily across the higher elevations. 
With southerly flow solidly in place, low temperatures this 
morning will be significantly warmer than yesterday, with 
temperatures in the low-mid 60s for the morning commute. 
With the aforementioned front lifting through the region today,
the result will be warmer temperatures today, with highs in the
mid to upper 80s, but it will also result in much more oppressive
dew points (approaching 70). Could see some showers and storms
develop near the warm front later this morning into early
afternoon. Latest guidance continues to show something forming,
but doesn't really seem to have the instability/shear for a
great severe threat. Some of the hi-res guidance paints a swath
of higher QPF this afternoon in central VA associated with this
warm frontal precip. So, will have to monitor that potential,
but not seeing anything to suggest a potential for flooding at
this time.
Meanwhile, a shortwave trough will push through the Great Lakes,
with an area of surface low pressure tracking along with it. 
The cold front associated with the low will approach the area 
from the west late this afternoon into the evening. A line of 
showers and thunderstorms is expected to push through at least 
western portions of the region late this evening. The Storm 
Prediction has western portions of the CWA in a slight risk for 
severe weather as a result, with areas east of the Blue Ridge 
only in a marginal, as the storms should run out of steam as
they track to the east. However, if the line does get organized
enough, it could very well maintain itself and track east along
the warm front. This could lead to increased severe threat east
of the Blue Ridge. At this time, not much guidance is 
supporting that, but will have to monitor the development of the
line as it approaches. 
With the weak cold front near the Chesapeake Bay by early Tuesday 
morning, any chance of showers will be coming to an end with drying 
westerly flow. Some moisture banked up against the Appalachians may 
result in a few showers along the Allegheny Front through the 
morning. Otherwise, the front is cold in name only, with high 
temperatures near or even slightly warmer than what they will be 
today (mid 80s - low 90s), with downsloping offsetting any minimal 
cold advection. Dew points will be lower though, making it feel less 
humid. There will also be a breeze, which will be strongest in the 
Surface high pressure will build across the area Tuesday night 
through Wednesday night. With weak flow, the very warm airmass will 
remain in place, although dew points will be slower to rise through 
the lower and mid 60s. There will be a trough to the northwest on 
Wednesday, and some convection may fire along it. Some of these 
showers and storms may approach the Potomac Highlands and northern 
Maryland late in the afternoon or evening, but should be in a 
dissipating state if they occur due to loss of diurnal heating and 
the strong ridge to the southeast.
The mid and upper level ridge will be building Thursday and Friday 
while the surface high remains nearby. This should largely suppress 
convection, though wouldn't totally rule out a stray "airmass" 
shower or storm with increasing humidity and potential for terrain 
circulations and subtle perturbations in the flow. More areas will 
likely reach highs in the 90s. Current most-likely heat index 
forecasts range from 95-100, short of headline criteria. Overnight 
lows may fail to drop below 70, especially by Friday night.
Heights begin falling Saturday as a closed low drops from Hudson Bay 
toward New England. This may result in a little better chance for 
pop-up storms. There is still some model spread on the timing of the 
associated cold front dropping southward through the area, which 
could ultimately determine which day of the weekend has the highest 
storm chances. If this front can indeed press south sometime over 
the weekend or early next week, there should be a slight reprieve 
from the heat.
VFR conditions are expected to prevail today across the region.
Showers could approach MRB by mid-late morning. Showers and
storms become much more likely in the afternoon/evening hours at
all terminals, but especially MRB. Could see very heavy
rainfall, along with some gusty winds, so restrictions to IFR
are a possibility. Generally expecting flow out of the SW at
5-10 kts throughout the day, but again, could see some higher
gusts in stronger thunderstorms, especially at MRB. Rain chances
decrease through tonight, with VFR conditions expected to
prevail once more. 
Westerly winds may gust to around 20 kt Tuesday behind the weak cold 
front, and VFR conditions will prevail. High pressure will build 
across the area Wednesday through Friday. Storm chances will be 
minimal and winds will be light.
Southwest flow expected today across the region, which will lead
to some enhanced wind gusts on the waters, which will reach SCA
criteria in the central Bay, so have maintained the Small Craft
Advisory for that area this afternoon through tonight. 
Winds will turn westerly early Tuesday morning in the wake of a weak 
cold front. There could be several hours of marginal SCA conditions, 
especially across northern parts of the Bay, but don't have the 
confidence to issue an advisory at this time.
High pressure will then build over the area Wednesday through 
Friday. Winds will be from a southerly or westerly direction and 
should remain below advisory criteria. A pop-up storm in heat and 
humidity can't totally be ruled out, but chances are very small.
MARINE...Small Craft Advisory from noon today to 6 AM EDT Tuesday for