Area Forecast Discussion
Issued by NWS Sterling, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
000
FXUS61 KLWX 240112
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
912 PM EDT Fri Sep 23 2016

.SYNOPSIS...
A cold front will cross the area late tonight and early Saturday.
High pressure returns to the region late Saturday and Sunday before
moving off the coast Monday. A cold front will slowly pass through
Tuesday into Wednesday. High pressure will return for late next
week.

&&

.NEAR TERM /THROUGH SATURDAY/...
Latest surface analysis suggests that the cold front stretches
across southern New England to the New York-Pennsylvania border.
There is minimal moisture of forcing associated with it, so the
most that can be expected is a band of clouds and north winds.
Latest indications are that will happen just before sunrise
Saturday. So most of the night will be mostly clear and calm.
Although there will be some radiational cooling, a warmer start to
the night and dewpoints in the 60s indicate that lows Saturday
morning will be warmer than this (Friday) morning.

Clouds will hang around for a great deal of Saturday before
gradually clearing from north to south in most of the area.
Temperatures should be generally 5 degrees cooler in our southern
regions and at least 10 degrees cooler further north across the
metro and close to Pennsylvania. As the front stalls in
central/southern Virginia, some weak instability and flow becoming
more upslope may cause a few showers to form tomorrow afternoon in
west-central Virginia.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
The front will nudge a bit further south of our region Saturday
night as high pressure from Canada builds further southeast. For
much of our area this will clear things out and result in the
coolest night since before Summer started...with widespread 50s
and perhaps some high 40s. However...in west-central
Virginia...upslope flow may be moist enough to generate some low
clouds...drizzle or spotty showers. This should gradually
dissipate during the day Sunday as temps warm up but clouds may
linger. Further north and east across the metro...most areas
should be mostly sunny and cool on Sunday with highs also expected
to be the coolest since before Summer started...with low 70s
common and some areas failing to crack 70. Sunday night looks
relatively similar to Saturday night...with upslope
clouds/drizzle/showers possible in west-central Virginia...but
mostly clear and cool conditions further north and east across the
metro.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Mid/upper-level ridge axis will move over the area Monday as surface
high pressure departs into the western Atlantic. 850 mb temperatures
will begin to warm but easterly to southeasterly onshore flow at in
the low levels will lead to increased cloud cover and cooler
temperatures.

Model solutions diverge significantly after Monday. The uncertainty
seems to stem from the strength of ridging downstream over the
western Atlantic and how quickly it allows an incoming trough to
approach from the west. The GFS has exhibited significant run-to-run
timing differences and GEFS/EC members also exhibit large timing
spread. The timing will also affect the trajectory and duration of
moisture return which will impact just how much rain we are able to
see as the trough approaches during the middle of next week.

Models continue to diverge for late next week with some indicating
the trough departing while others develop a cutoff low near or just
east of the CWA. At this time, it appears the highest precipitation
chances would be in the Tuesday to Wednesday time frame with a
gradual return to fair weather by the end of next week. After a
brief cool down behind the mid-week front/trough, another warming
trend seems likely by the end of next week as strong ridging builds
over the lower Mississippi/Tennessee River Valleys.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
VFR through Saturday. Its still possible that patchy fog may
develop near KCHO tonight. While the fog coverage has increased in
the grids, there have been no changes made to the TAF sites at
this time. Front will cross the terminals late tonight and early
Saturday with a wind shift to a more northerly direction along
with a few gusts...along with some clouds at around 5k ft or so.
Clouds may linger near CHO Saturday night and Sunday but should
clear elsewhere.

Sub-VFR possible with lower ceilings as a result of onshore flow
Monday, then with possible showers ahead of an approaching front
Monday night through Tuesday. Southeasterly winds around 10 knots
Monday will gradually veer around to the southwest by late
Tuesday.

&&

.MARINE...
Winds from the south this evening, but at speeds below 10 kt.
There may be a slight increase in wind speeds ahead of an
approaching cold front, but latest guidance suggests that 20 kt
gusts will hold off til the northerly flow behind the frontal
passage. That will take place during the hours around sunrise
Saturday. Therefore, have dropped the Small Craft Advisory for
the overnight hours, but will maintain it for the morning-midday
hours Saturday. Winds should diminish Saturday afternoon and
generally sub-SCA winds after that through Sunday night.

Southerly channeling/Small Craft Advisory level gusts along
with an increasing threat for showers are anticipated ahead of an
approaching front late Monday into Tuesday.

&&

.TIDES/COASTAL FLOODING...
Anomalies remain elevated, but caution stages appears to be where
sensitive locations will top out with the incoming tide.
Saturday`s tides should be a little bit lower due to northerly
flow across the estuary. However as winds shift more easterly
Sunday and then southeasterly Monday...anomalies could increase
once again, and risk of tidal flooding may rise.

&&

.CLIMATE...
Unusually warm weather has persisted over the area for
quite some time. Autumn-like temperatures will finally make an
appearance over the weekend likely bringing low temperatures at
DCA below 60 degrees for the first time since June 9th, or 105
days ago. The record most consecutive days at or above 60 degrees
in the Washington DC area is 112 set in 2012.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from 6 AM to 2 PM EDT Saturday for
     ANZ530>534-537>543.

&&

$$
SYNOPSIS...RCM
NEAR TERM...HTS/RCM
SHORT TERM...RCM
LONG TERM...DFH
AVIATION...HTS/RCM/DFH
MARINE...HTS/DFH
TIDES/COASTAL FLOODING...HTS
CLIMATE...DFH



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.