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Area Forecast Discussion (AFD)

Issued by Buffalo, NY (BUF)

                            
884 
FXUS61 KBUF 181450
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
950 AM EST Sun Feb 18 2018

.SYNOPSIS...
Outside of some lingering snow showers east of Lake Ontario,
fair weather will return today as high pressure passes to our
south. Then there will be a dramatic warm up for the first half
of the work week when temperatures will soar well into the 60s 
and possibly to 70. This will be the warmest weather since last 
October.

&&

.NEAR TERM /THROUGH TONIGHT/...
A shortwave trough will move across New England while a large area 
of high pressure moves south of the Great Lakes this morning.
Radar shows a fairly well organized but narrow band of lake
enhanced snow east of Lake Ontario late this morning. This
should drift south late this morning before lifting north and
weakening this afternoon. Localized accumulation up to 2 inches
is possible, but accumulations will be limited due to the narrow
nature of the band and because it will be moving instead of
focusing on one location.

Satellite imagery shows a fairly persistent cloud deck which is
probably trapped beneath an inversion shown at about 800 mb by
the 12Z Buffalo sounding. Model guidance advects drier air
associated with high pressure, with clouds expected to 
dissipate from south to north this afternoon. The latest 
forecast has a slightly slower clearing trend with slightly 
cooler high temperatures due to the more persistent cloud cover.
Temperatures will climb into the mid 30s to around 40.

High pressure moves off the Mid-Atlantic coast this evening and 
winds become southwesterly across the eastern Great Lakes. Warm air 
advection will cause clouds to increase from southwest to northeast 
overnight. Temperatures will drop into the 20s this evening before 
climbing back into the 30s by Monday morning. Low temperatures will 
be reached this evening.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Wet weather still looks likely during this period. 

Longwave trough over the western CONUS develops this period with a 
gigantic subtropical ridge off the southeast coast. Quasi-stationary 
baroclinic zone to set up in between with copious moisture advection 
flooding into the Midwest and Great Lakes. Front aligned nearly 
parallel to the mean flow and expect several rounds of rain with 
slow ejection of western CONUS trough. 

Initial theta-e surge arrives Monday afternoon with our first good 
shot of widespread rain. Could even see a few elevated thunderstorms 
with this initial surge, though instability profiles are a little 
too marginal to introduce thunder at this stage. Not expecting much 
impact with this initial rain. 

Potential problems will arise Tuesday into Wednesday as several 
waves ripple along baroclinic zone. At this point, it looks like the 
front will move northward across the area setting up across northern 
portions of the area Monday night into Tuesday, eventually remaining 
in the vicinity of the central Great Lakes into the Saint Lawrence 
Valley. Another round of moderate, and possibly heavy rain with 
embedded convective elements is expected late Tuesday into Wednesday 
as the front sweeps southeast, but there will likely be a 
substantial break during this period for a good portion of the 
area that emerges into the warm sector. 

While the pattern certainly favors heavy rain somewhere, with 
precipitable water values exceeding an inch along active quasi-
stationary front, eventual swath of heavy rain is often narrower 
than what coarse global models suggest. Certainly worth keeping an 
eye on, but confidence in exact rain amounts and locations remains 
low. 

Unseasonably warm conditions also expected during this period. 
Several guidance packages now suggesting temperatures Tuesday 
afternoon will likely jump into the upper 60s to lower 70s across 
most locations. Coolest readings will remain northeast of the lakes 
with a stiff southwest wind in place, which may keep temperatures 
along the immediate lake shore areas in the 50s. Both daily record 
high temperatures and record warm low temperatures are likely to be 
broken during this stretch. 

With the increased confidence in large-scale snowmelt due to the 
warm temperatures and resultant river rises, ice break-up and/or 
potential ice jam flooding remains the greatest threat with this 
event and a Flood Watch has been issued Monday night into Wednesday 
for Jefferson, Lewis, and Oswego counties where an extensive 
snowpack remains. This flood potential will include the Black River.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
Widespread rain shifting east across our region Wednesday night 
will likely mixing with and changing to some snow showers.

Strong dry high pressure should then build over the Great Lakes 
Thursday/ Thursday night. There is a low chance of some rain and 
snow showers on Thursday depending on the speed of the front but 
mainly dry weather should be expected. Model consensus then shows 
another warm front or surface low crossing our region Friday night 
into Saturday likely leading some rain and/or snow showers Friday 
night and chance or rain showers Saturday.

Temperatures Wednesday will be highly dependent on the timing of the 
cold front but should likely remain above normal. Temperatures will 
fall back toward normal Thursday through Saturday but likely 
remaining 5-10 degrees above mid-late Feb normals.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
Cloud cover will linger into this afternoon, with bases above 
3k feet in all locations except the higher terrain of the 
Southern Tier which includes JHW. Expect clouds to go from BKN-
SCT this afternoon with widespread VFR conditions by late 
afternoon as high pressure passing to the south ridges into the 
region. Mid- level clouds will increase from southwest to 
northeast overnight.

Outlook... 

Monday...Deteriorating to MVFR to IFR in rain.
Monday night and Tuesday...Generally VFR to MVFR in showers but IFR 
across the North Country in more widespread rain.
Wednesday...MVFR in moderately heavy showers.
Thursday...VFR.

&&

.MARINE...
Winds will briefly meet small craft criteria into this 
afternoon across eastern portions of Lake Ontario. Winds and 
waves will subside tonight and Monday...as the next area of high
pressure will pass to the south.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...Flood Watch from late Monday night through Wednesday evening 
     for NYZ006>008.
MARINE...Small Craft Advisory until 4 PM EST this afternoon for LOZ043-
         044.

&&

$$

SYNOPSIS...HSK/APFFEL
NEAR TERM...APFFEL/HSK
SHORT TERM...TMA
LONG TERM...SMITH
AVIATION...APFFEL/HSK
MARINE...HSK/APFFEL