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FXUS61 KLWX 240112

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
912 PM EDT Fri Jun 23 2017

Tropical air will envelop the area today. A cold front will 
cross the area late tonight into Saturday. High pressure will 
return Sunday and persist through early next week.


Besides a few showers across the region late this afternoon and
early this evening...the LWX CWA has been quiet especially compared
to our neighbors to the west and north. This will change tonight
as remnants of TD Cindy and a cold front will move into the 
Mid- Atlantic region. Showers will spread across the region 
tonight with embedded heavy showers and gusty winds. The 
atmosphere is moist with an observed PWAT from KLWX of 1.9 at 
00z. Sfc dewpts in the 70s will give to moderate instability 
across the region tonight. Shear is also moderate with near 
50kts of 0-6km bulk shear. Thunderstorms are possible as the 
cold front crosses the region overnight. Hi-res guidance depicts
some line segments that may produce stronger winds and severe 
thunderstorm warnings can not be ruled out overnight. Seems like
the best chance will be across the northern half of the outlook
area. Rainfall amounts of 0.75- 1 in are expected across the
northern half and will taper off to around 0.25 in across the
Central Foothills/southern MD overnight with higher amounts in 
heavier bands/thunderstorms.

Elsewhere...a strong LLJ will be on top of the region tonight 
and widespread showers will likely bring down gusty winds. 
Gusts 35-45 mph can not be ruled out across the region into 
early Saturday morning. The cold front should cross the region 
by 8AM Saturday morning and drying will occur behind it. 

Prev discussion...
Latest GFS/NAM prog timing to be so quick that all precip will
be east of the forecast area by the start of the period. Am a
little bit caution of that solution, and have lingered some
precip into the Saturday morning hours. Then we'll need to
assess how quickly front leaves area; there are some suggestions
in may get caught up across southern Maryland or the Virginia


High pressure will be building across the area this weekend, 
with no other weather hazards. Perhaps there will be a 
reinforcing boundary Sunday, but moisture looks scant for even 

Accepted a MOS blend for temps. Sunday will be the cooler day,
with lower dewpoints also advecting in Saturday.


Surface high pressure sets to the west on Monday as a slow 
moving upper level trough slides east into Tuesday with surface 
westerly flow. Below normal temperatures, with showers and 
thunderstorms possible during this period. 

Conditions should become drier as surface high settles overhead 
Tuesday night. The high will move offshore on Wednesday and continue 
moving west into Thursday as flow becomes more southerly. 
Temperatures will be on the rise as dry conditions continue into 
Friday, when guidance suggest a boundary will bring showers and 
thunderstorms over our area.


A cold front, infused with tropical moisture, will cross the 
terminals tonight, most likely after midnight but before dawn. 
At this point, kept restrictions at MVFR. There is a decent 
potential of local/brief IFR, probably due more to reduced vsbys
in heavy rain. There may also be localized wind gusts. Where 
these gusts aren't realized, there is a 50-70 kt wind max 
several thousand feet off the deck, so low-level wind shear will
be a concern.

The front will be east of the terminals by Saturday morning. VFR
conditions will prevail for the weekend.

Mostly dry/VFR conditions expected Monday into Wednesday as 
surface high pressure settles in. Some scattered showers and 
thunderstorms possible Monday afternoon into Tuesday as upper 
air disturbance moves through, which could cause periods of sub-
VFR conditions.


Update...A Gale Warning is in effect for all waters late 
tonight into Saturday morning. Showers and thunderstorms will be
capable of producing gusty winds on the waters during this 

Southwest winds 10-15 kt with some gusts to 20 kt. Those winds
will be increasing ahead of a cold front tonight. Small Craft
Advisories remain in effect. There will be a 50+ kt low level 
jet several thousand feet off the waters overnight. Do not 
believe this will mix down in the gradient flow, but local 
punches may near heavier showers. Marine Warnings may be 
required tonight.

Northwest flow Saturday will contain better mixing. The
gradient will decease Saturday night. Have not extended the 
Advisory further at this time.

Mostly dry conditions expected Monday into Wednesday as surface
high pressure settles in. Some scattered showers and 
thunderstorms possible Monday afternoon into Tuesday as upper 
air disturbance moves through. Winds gusts will be below the 
small craft advisory criteria.


As mentioned above, precip waters will be exceeding 2 inches, so
heavy rain expected in storms tonight. However, only 0.1 to 0.3
inches fell this morning, so soils were not saturated. Further,
storms look to be progressive. So, while heavy rain expected,
believe that the soil will be able to handle it overall, based
on flash flood guidance. Thus, will not post any Watches at this
time. Local minor flooding is possible, especially in the 
Potomac Highlands.


A coastal flood advisory is in effect for Anne Arundel,
Baltimore and Harford counties late tonight into Saturday
morning. Anomalies around one foot are expected during this

Beyond that, northwest winds should lead to levels returning 
close to normal.


MD...Coastal Flood Advisory from 2 AM to 2 PM EDT Saturday for 
MARINE...Small Craft Advisory until midnight EDT tonight for ANZ530>543.
     Small Craft Advisory from 8 AM to 6 PM EDT Saturday for 
     Gale Warning from midnight tonight to 8 AM EDT Saturday for 


SYNOPSIS...RCM are expected during this

Beyond that, northwest winds sho

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