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FXUS61 KLWX 240850

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
350 AM EST Sat Feb 24 2018

A stationary boundary situated across our area will gradually lift 
northward as a warm front through Sunday. A cold front will then 
pass through from the west by Sunday evening, with high pressure 
building in to the region through early next week.

Much of the area is covered in low clouds early this morning that 
are trapped below a hefty inversion based just a couple thousand 
feet off the ground, as sampled by the 00z KIAD sounding. Atop this 
inversion is a nice wedge of warm air aloft, with temperatures in 
the middle 50s at about 5kft. Back at the surface, temperatures 
early this morning range from the lower 40s west of the Blue Ridge 
to middle to upper 40s along and south of the D.C. metro area. Areas 
of dense fog have been persistent, relegated mainly along and north 
of the District, encompassing Baltimore and northeast MD. A Dense 
Fog Advisory remains in effect until 8am this morning for these 

Outside of light drizzle in the fog plagued areas, the KLWX radar is 
mostly echo free. Do expect this to continue to be the case much of 
the morning across the area, at least east of the Blue Ridge 
mountains. We will start to see some showers encroach on our western 
and northern zones mid to late morning hours as a wave of low 
pressure moves northeastward over southern OH and WV. A stationary 
boundary snaking down the Appalachians and across North Carolina 
this morning will gain some momentum later today and gradually lift 
northward as a warm front through our area into tonight. As a 
result, highest rain chances will be this afternoon through the 
overnight period. Heaviest rain will be found across western MD, the 
Potomac Highlands, and the West Virginia Panhandle, where a half 
inch to an inch of rain could fall by Sunday morning. East of these 
areas, a tenth to a quarter of an inch can be expected, with lowest 
amounts across southern MD. With much of the area residing on the 
cool side of the frontal boundary today, temperatures stick in the 
upper 40s over northern MD to the middle 50s surrounding the metro 
areas. The locations favored to reside on the warm side of the 
boundaries are the southern portions of the Northern Piedmont, 
Central Foothills, and the Virginia Highlands, where highs will near 
60 degrees and in to the middle 60s for the warm spots. Lows tonight 
won't budge much, with middle 40s to our north to middle 50s to the 

Come Sunday morning, a cold front will be moving eastward and 
nearing the western portions of our CWA. The aforementioned warm 
front will be lifting through and north of our area by Sunday 
morning, allowing much warmer temperatures to prevail. High 
temperatures will near 70 degrees for much of the area, with the 
cooler middle to upper 60s over the northern third of the CWA. 
Scattered shower activity Sunday morning will increase by midday as 
the front nears from the west. With the warmer temperatures and 
dewpoints creeping in to the lower 60s, along with frontogentical 
forcing, a slight chance of thunderstorms is possible as the front 
crosses the region by Sunday evening. Behind the front, clearing and 
drying conditions will win out Sunday night, with temperatures still 
above normal for late February, ranging from near 40 degrees to the 
north/west to around 50 degrees along our southern border. 

High pressure will build in from the west as we kick off the work 
week. The frontal boundary will linger along the Carolina coast on 
Monday, with the ECMWF indicating at least some rain chances for our 
southern zones. As such, will keep chance POPs for these areas on 
Monday, but the majority of our CWA will remain dry. Weak CAA behind 
the front on Monday will not prevent temperatures from reaching the 
upper 50s on Monday, with lows Monday night cooler in to the 30s 
area wide as CAA is a bit stronger and 850 temperatures reside at or 
just below 0C. This is in response to a low/mid level trough 
swinging through the region Monday evening.

The middle of the week will be quiet as high pressure will be 
overhead. Tuesday will be the sunnier day; moisture will advance 
Wednesday due to return flow/warm advection as the center of the 
high will move into the western Atlantic. It remains to be seen if 
there will be any showers. GFS pointing that way more than ECMWF. 
Will back off PoPs for the period. 

Have greater confidence that the end of the week will end on the wet 
side, in spite of guidance timing/organizational differences. (ECMWF 
placing more emphasis on distinct southern stream shortwave/energy 
vs triple point from a well-defined northern stream system.)  Either 
solution provides strong evidence of measurable precipitation, and
neither scenario suggests there will be type issues until the back
side (Friday night), when the qpf will be exiting. 

Widespread LIFR conditions at all area terminals this morning as low 
clouds and areas of dense fog envelop the region. Winds remain calm 
to light, favoring a southerly trajectory when registered by surface 
observations. LIFR VIS/CIGs will continue through mid morning, with 
some improvement to VIS, at least in terms of fog coverage, but low 
clouds and drizzle will persist. Rain chances increase this 
afternoon and evening as a wave of low pressure passes to the 
northwest of the terminals. Highest rain chances will be at MRB, but 
continued LIFR conditions expected through tonight. 

A cold front will move through the terminals Sunday afternoon, with 
plentiful rain chances and IFR/LIFR VIS/CIGs continuing ahead of it. 
Southwesterly breezes at around 10 knots, gusting to near 20 knots 
during the day on Sunday, will shift out of the northwest Sunday 
night and fall to less than 10 knots in the wake of the frontal 
passage. Conditions should improve to MVFR/VFR Sunday night, and 
back to VFR through Monday night as high pressure moves in from the 
west. Exception to this on Monday would be CHO, where some residual 
shower activity is possible as the aforementioned boundary lingers 
well to our south. This could result in periods of sub VFR 
conditions there.

VFR conditions expected at this time due to high pressure.

No advisories expected through tonight for our waters as winds will 
remain light as a stationary boundary to our south starts to lift 
northward as warm front. As a cold front approaches from the west on 
Sunday, winds will pick up and become gusty out of the south 
southwest Sunday morning, with SCA conditions looking likely through 
much of the day on Sunday until the front passes through our waters. 
The frontal passage may bring with it a gusty line of showers, with 
a slight chance of thunderstorms as well. High pressure will then 
build in to the region behind the front through Monday night, 
delivering lighter winds across our waters, and sub SCA

Winds will remain below Small Craft Advisory thresholds due to high 
pressure. Southerly flow will increase late Wed in the wake of the 

DC...Dense Fog Advisory until 8 AM EST this morning for DCZ001.
MD...Dense Fog Advisory until 8 AM EST this morning for MDZ003>006-
VA...Dense Fog Advisory until 8 AM EST this morning for VAZ053-054-
WV...Dense Fog Advisory until 8 AM EST this morning for WVZ052-053.



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