Area Forecast Discussion


677 
FXUS61 KLWX 220815
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
315 AM EST Fri Feb 22 2019
.SYNOPSIS...A front will stall across the Carolinas through 
tonight as high pressure builds to the north toward New 
England. Low pressure developing over the middle Mississippi 
River Valley will strengthen as it moves northeastward across 
the Great Lakes into Canada this weekend. High pressure will 
build from the northern Great Plains toward the Great Lakes and 
eventually into the northeast through the first half of next 
week. Low pressure developing over the Tennessee Valley could 
approach the region during the middle of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
The dew point gradient is the best way to discern a subtle boundary 
moving southward across the Mid-Atlantic early this morning. The 
main surface front/temperature gradient is draped across central 
North Carolina. Both of these boundaries will sink southward and 
stall through the day today.
A weak wave of low pressure passing to our south will likely 
continue to force a bit of light rain across central Virginia and 
far southern Maryland until about mid morning, after which time 
northerly winds should push rain to the south, limiting to the I-64 
corridor through the rest of the day.
Lots of mid and high level clouds are expected today in overrunning 
well north of the stalling surface boundary, and should keep highs 
generally in the lower to middle 40s.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Surface high pressure will be building to the north over upstate New 
York and into New England tonight (~1035 mb). This is an ideal spot 
to lock in some cold air near the surface, but the antecedent 
airmass isn't abundantly cold. Temperatures are expected to fall to 
around freezing for elevations above 1500 feet tonight, and across 
northern Maryland, the eastern West Virginia panhandle and 
northwestern Virginia.
Precipitation likely holds off until after daybreak Saturday, except 
perhaps across west-central Virginia, which should allow 
temperatures to rise some. Still, freezing rain seems likely at 
least across the ridgetops along and west of the Blue Ridge and into 
western Maryland, possibly the eastern West Virginia panhandle 
Saturday morning through about midday. This is as precipitation 
develops in strengthening overrunning ahead of a deepening surface 
low over the Midwest.
Continued warm advection should push temperatures above freezing 
Saturday afternoon, though some hi-res guidance like the 00Z NAM 
Nest wants to hold onto freezing temperatures over the ridges until 
Saturday evening. Lower elevations should see all rain (except 
perhaps over northern Maryland near the Pennsylvania border).
The latest guidance has trended southward a bit with the heaviest 
precipitation amounts Saturday night, likely in part due to high 
pressure to the north nosing some drier low-level air into the 
region. Strong warm air advection may overcome this some, but the 
best upper jet forcing is displaced to our northwest closer to the 
parent surface low (likely to track over Lake Michigan Saturday 
night). This could help keep rainfall amounts near or a little under 
one inch, but even that could result in minor flooding given 
saturated ground and recent snowmelt, particularly over eastern West 
Virginia this weekend.
There may be a few heavier showers along the approaching cold front 
early Sunday morning. I could see the warm front never truly making 
it fully through the area given the high to the north and the parent 
low being so far west, but Sunday is still expected to be very mild 
since appreciable cold air advection lags well behind the surface 
front, and downsloping westerly flow/compressional warming should 
push highs well into the 60s. Winds will likely be very gusty Sunday 
with a strong pressure gradient behind the front, possibly reaching 
or exceeding advisory criteria (greater than 45 MPH).
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
The weather pattern will be largely dominated by a broad trough
aloft across eastern North America and strong Canadian high 
pressure at the surface. As a result, temperatures will stay 
cooler than normal and it will be much drier than it has been 
lately. On Monday, a tight pressure gradient will still exist 
over the region associated with a deep cyclone over Atlantic 
Canada, but the winds will not be as strong like on Sunday, but 
still windy nonetheless. Overall, fair weather is expected much
of next week but on the chilly side.
&&
.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Mainly VFR today. MVFR INVOF CHO should lift around mid morning, 
though spotty -RA may linger into this afternoon. CIGs expected to 
lower to IFR by late Saturday as a warm front slowly approaches from 
the south, with rain overspreading the area Saturday afternoon. Some 
freezing rain is possible near MRB Saturday morning, if 
precipitation moves in quickly enough while temperatures are still 
near or below freezing. Winds will generally be N to NE AOB 10 kts.
VFR likely returns by Sunday afternoon with gusty W winds 35+
kts. 
Still windy on Monday with gusts likely in the 25-35 kt range.
Winds diminish further on Tue but still breezy with gusts in 
the 15-25 kt range.
&&
.MARINE...
A subtle uptick in northerly winds is possible early this morning 
behind a weak moisture boundary pressing southward. An isolated 18 
knot gust is possible during this time. Otherwise, generally light 
north to northeast flow is expected through Saturday night.
Rain is expected to overspread the waters Saturday into Saturday 
night as the aforementioned boundary returns north as a warm front. 
Whether or not the warm front makes it through the waters before a 
cold front approaches from the west by Sunday morning remains to be 
seen, but there is moderately high confidence in gale force winds 
later Sunday into Sunday night in westerly flow behind the
front.
Marginal gales will still be possible on Mon. Otherwise, strong
SCA conditions Mon-Mon evening. SCA conditions possible again on
Tue and Wed.
&&
.HYDROLOGY...
Given recent snowmelt and saturated ground, three quarters of an 
inch to around an inch of rain may be enough to result in minor 
flooding issues this weekend, particularly over eastern West 
Virginia. The overall trend has been for slightly less rain, but not 
so much less to completely avoid a flood threat. Despite the 
slightly lower QPF totals in the 00Z model suite, MMEFS still 
indicates >50% chance of minor flood at several river forecast 
points later this weekend.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...Winter Weather Advisory until 10 AM EST this morning for 
     VAZ503.
WV...Winter Weather Advisory until 10 AM EST this morning for 
     WVZ505.
MARINE...None.
&&
$$
SYNOPSIS...LFR
NEAR TERM...DHOF
SHORT TERM...DHOF
LONG TERM...LFR
AVIATION...LFR/DHOF
MARINE...LFR/DHOF
HYDROLOGY...DHOF