National Weather Service Raw Text Product

706 
FXUS61 KLWX 121509
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1109 AM EDT Sun Mar 12 2017

.SYNOPSIS...
High pressure will build over the region through early Monday. 
Surface low pressure will impact the Mid-Atlantic Monday night 
into Tuesday with upper level low pressure then over the area 
through Wednesday. High pressure will build toward the area 
Thursday through Friday with a cold front crossing the area 
Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Cold and dry weather continues today...with daytime highs still
~15F below climatology. Wind gusts still peak near 15-20 mph 
during the afternoon...which will keep wind chills AOB M30s 
despite afternoon highs near 40F.

Another cold night tonight with lows dropping into the 20s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
All eyes continue to be on major winter storm set to impact the
area Monday evening through Tuesday...as coastal low rapidly 
intensifies as it traverses northeastward along the eastern 
seaboard. 

SREF continues to trend lower on snowfall totals in the central
Shenandoah Valley...while keeping the heaviest snowfall across 
PA. But our southern area may still receive 5-6" totals. It is 
possible that we may add this area to the watch early this 
afternoon. 

12Z NAM is in and looks along the lines of what Euro has been
portraying since Friday - coastal low forms south of the Outer
Banks Monday evening...moving east of the Delmarva by 12Z
Tuesday..and deepens rapidly as it approaches Block Island
Tuesday afternoon. 

As has been postulated for the past few days the highest totals
will be west of I-95 and closer to the PA border. The Bay water
temperature is around 43 degrees. An easterly wind component
would bring moderated air east of I-95 which could work to keep
totals lower - perhaps more SG/IP. But models show the
best vertical motion in the 06-12Z timeframe: travel is highly
discouraged overnight Monday night as snowfall could be moderate
to heavy during that time west of the cities.

Our 10-50-90 snowfall products continue to reveal the large 
spread...as for DC/Balt 10th percentile is 2-4...50th percentile
is 6-9...and 90th percentile is 11-15. Thus, it is imperative 
that interested parties continue to follow the forecast as 
changes are expected.

Believe this storm will wind down rapidly Tuesday
afternoon...although it will continue to be cold with gusty
northwest winds. Snow showers will be possible east of the
mountains...while in the Highlands an extended period of upslope
snow is expected.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As the storm slowly continues to pull away Wednesday, gusty
northwest flow will continue as high pressure to the west tries
to build eastward. Temperatures will remain well below normal
and as an upper low moves east across the area, snow showers
will be common. This low will be retreating east by late 
Wednesday, but another shortwave looks to rotate southeast 
across the region on Thursday. This could result in a few 
additional snow showers, though as this shortwave is much 
weaker, the odds of this are substantially lower on Thursday 
than on Wednesday. Either way, it will remain very chilly 
Thursday, though not quite as cold as Wednesday, and winds will 
be lighter as the pressure gradient relaxes and high pressure 
builds into the Ohio Valley. High pressure builds overhead 
Friday with a more noticeable moderation in temperatures, though
they will still be below normal. Further moderation is likely 
as winds become southerly on Saturday just ahead of the next 
cold front. Some showers are also possible, and p-type is not 
yet certain to be rain given temps aloft will still be chilly, 
though rain will be more likely than the system early this week.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
VFR conditions will prevail today through midday Monday. Low 
pressure will begin to initiate flight restrictions starting as 
early as Monday afternoon for KCHO and then Monday evening into 
Tuesday for all terminals. Accumulating snow is likely 
during...with periods of heavy snow possible (especially late 
Monday into Tuesday morning). Rain may mix with snow at times 
(mainly at DCA/BWI/MTN).

Sub-VFR restrictions due to gusty NW wind and possible snow
showers or even squalls on Wednesday. Chance of snow showers
lowers Thursday and drops to zero Friday with solid VFR
expected, along with lighter winds.

&&

.MARINE...
Decent mixing will produce marginal SCA conditions this 
afternoon across northern portions of the Chesapeake Bay...SCA 
issues for this area for the afternoon through early evening. 

After a brief respite in winds Sunday night through Monday 
afternoon...SCA gusts develop rapidly late Monday afternoon as 
coastal low begins to impact the area. Solid SCA gusts continue 
through Tuesday night...with gales possible depending on the 
track of the low. 

Gales will remain possible Wednesday as the coastal storm slowly
departs. Winds will gradually drop off Thursday but gales could
still occur - odds are lower, though. By Friday, winds should
drop significantly, perhaps below SCA.

&&

.CLIMATE...
Here are the daily minimum high temperature records for March 
12th.

March 12th
Site   Record daily cold high
DCA    30 degrees (1900/1888)
BWI    29 degrees (1984)
IAD    36 degrees (1998/1984)

The presence of a fresh snow pack may allow particularly cold
air on Thursday night when a high pressure ridge builds 
overhead.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Winter Storm Watch from Monday evening through Tuesday 
     afternoon for DCZ001.
MD...Winter Storm Watch from Monday evening through Tuesday 
     afternoon for MDZ003>006-011-013-014-501>508.
VA...Winter Storm Watch from Monday evening through Tuesday 
     afternoon for VAZ027>031-039-040-051>055-501-502-505>508.
WV...Winter Storm Watch from Monday evening through Tuesday 
     afternoon for WVZ050>053-055-501>504.
MARINE...Small Craft Advisory from 2 PM this afternoon to 8 PM EDT this 
     evening for ANZ530-531-538-539.

&&

$$
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