National Weather Service Raw Text Product

782 
FXUS61 KLWX 120801
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
401 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. Though, relatively lighter winds 
(compared to Saturday) combined with increasing sun by afternoon
will make it feel a little nicer. However, wind gusts still 
peak near 15-20 mph during the afternoon...which will keep wind 
chills AOB M30s despite afternoon highs near 40F.

Another very cold night  tonight...with lows dropping into the 
20s as dry airmass cools efficiently.

&&

.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. Winter Storm Watch continues for much of the area. 
Allegany, Mineral, and Grant were added to the Watch.

Tricky forecast continues...as transition line will likely 
wreak havoc with snow totals wherever it ultimately sets up. 
While some intermodel consistency has developed...intramodel 
spread (even within the same model family) continues to be 
extremely large (in some cases > 10 inches). Latest GEFS 
ensembles have cooled from earlier...with ptype largely snow 
across the DC/Balt corridor...and rain/snow mix across far S MD.
ECMWF ensembles also continue to suggest a similar sharp 
gradient across S MD. Sweet spot continues to be west of I95 to 
I81 from northern VA up into Pennsylvania...as this area will 
likely be co-located with deformation zone and thus will 
experience the greatest QPF (likely all snow). Furthermore, 
elevation is higher across this area...which will help to 
further enhance snow totals. This area could receive more than a
foot of snowfall for the entire event.

Bufkit profiles continue to suggest primary period of extreme 
lift through the dendritic growth zone occurs during a 12-15 
hour period late Monday through Tuesday morning. This is when 
snowfall rates could approach 1-2 inches per hour. While snow 
showers could continue through Tuesday night in wraparound 
precipitation...bulk of snow totals will occur from 00z-15z 
Tuesday.

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. 

&&

.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. Some could bring additional accumulations,
especially if they occur early in the day. 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 /07Z SUNDAY THROUGH THURSDAY/...
VFR condtions 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...
Stubborn wind gusts AOA SCA criteria continue across the waters
this morning. SCA advisory ongoing through 5 AM for all but the
upper tidal Potomac. Wind gusts should subside as daybreak 
nears...though portions of the SCA may need to be extended. 
Brief lull in winds through midday...then 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...
A shot of very cold late season Arctic air has arrived. Here 
are the daily cold temperature records for March 12th.

March 12th
Site   Record daily low   Record daily cold high
DCA    11 degrees (1900)  30 degrees (1900/1888)
BWI    12 degrees (1900)  29 degrees (1984)
IAD    18 degrees (1998)* 36 degrees (1998/1984)
*Also set in 1984/1969

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 until 5 AM EDT early this morning for 
     ANZ530>534-536-537-539>541-543.
     Small Craft Advisory from 2 PM this afternoon to 8 PM EDT this 
     evening for ANZ530-531-538-539.

&&

$$
SYNOPSIS...MSE
NEAR TERM...MSE
SHORT TERM...MSE
LONG TERM...RCM
AVIATION...MSE/RCM
MARINE...MSE/RCM
CLIMATE...LWX