Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 160836 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 336 AM EST Sat Feb 16 2019 .SYNOPSIS... High pressure centered over the Canadian prairies and a storm system over northern Quebec will maintain a cold northwest flow across our region into tonight. This will keep some light snow showers and flurries in place southeast of the lakes...although generally fair weather can be anticipated through the first half of Sunday. Low pressure moving from the Tennessee Valley to the Mid Atlantic region will bring us our next chance for widespread measurable snow late Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... A cold northwest flow in the wake of a deep storm system over northern Quebec will generate some nuisance light snow showers and flurries southeast of both lakes through the morning hours...but given a staunch subsidence inversion under 5k ft...any accumulations will be minimal. Otherwise...expansive high pressure centered over the Canadian prairies will arch to the southeast across the Great Lakes region for the afternoon. This will support fair uneventful weather across our region...with nothing more than some flurries and spotty light snow showers over the counties bordering the south shore of Lake Ontario. Temperatures today will fall short of normal....staying in the 20s for all but the normally milder Genesee Valley. Tonight...a low amplitude mid level ridge and an extension of the aforementioned Canadian surface high over will guarantee a fair night across the region. The only weather to speak of will be some flurries that will be found over the counties lining the south shore of Lake Ontario. It will be cold...with the mercury dipping into the teens over the western counties and the single digits for sites north and east of the Tug Hill. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... As this period opens on Sunday a few spotty flurries may still be ongoing along and a little inland from the south shore of Lake Ontario...with these supported by leftover shallow low level moisture and an east-northeasterly low level flow. These should fade by mid to late morning...with dry conditions otherwise prevailing through early to mid afternoon along with increasing mid and high clouds out ahead of the next system. Later Sunday afternoon and evening a modest southern stream system will track from the Tennessee Valley to about Pittsburgh...from which point onward it will slide eastward along the Mason-Dixon line and off the mid-Atlantic coastline later Sunday night and Monday morning. Over the past couple of days the various guidance packages have universally trended northward and come into much better agreement with the track of this system...with all guidance now suggesting a rough 18 to 24 hour-long period of steady light snow across much of our region between late Sunday afternoon/Sunday evening and the first half of Monday. With this in mind have continued the steady upward trend in PoPs...with these now raised to categorical south of Lake Ontario and to likely/chance across the North Country...where a fairly sharp northern cutoff to the snow still looks to be in place. Initially the snow should be forced by a combination of weak warm air advection and DCVA...followed by weak deformation and upsloping later on in the event. With the more northerly track to the system and deeper moisture and somewhat better forcing consequently available to work with...total snowfall amounts between late Sunday afternoon and Monday have come up a bit more...and now look to range on the order of 2-4 inches south of Lake Ontario to a half inch to an inch near the Saint Lawrence River. Should the current northward trend continue...it is not at all out of the question that amounts could potentially reach the lower end of the advisory range in places south of Lake Ontario...a mention of which will be added to the HWO. Stay tuned... Following the passage of this system...the cold but increasingly dry northwesterly flow in its wake may support a few more flurries or leftover snow showers Monday night and Tuesday...particularly closer to Lake Ontario. Otherwise expansive high pressure initially centered over the northern Plains states will steadily build southeastward across the Great Lakes and southern Canada...while bringing a return to dry and quiet weather to our region. As for temperatures...these will remain at below normal levels through this period...with daily highs ranging through the 20s... and nightly lows mostly ranging from the single digits across the North Country to the teens south of Lake Ontario. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... During the latter half of next week the flow across the eastern CONUS will become a bit more amplified as deepening large-scale troughing over the Rockies and western Plains states drives the development of downstream upper level ridging over the eastern third of the nation and the far western Atlantic ocean. Southern stream energy and another attendant broad/complex surface low ejecting northeastward within this flow regime still looks to push across the Ohio Valley and the Northeastern states between Wednesday and Thursday...with the medium range guidance continuing to exhibit some differences with respect to the track and timing of this system. These differences notwithstanding...it still appears that this system will bring at least the chance of precipitation to our area Wednesday into Thursday...with a cold enough airmass for primarily snow on Wednesday eventually warming enough to support the potential for mixed precipitation or even rain Wednesday night and Thursday. At the same time...the overall warm advection regime should also allow temperatures to climb back to a little above late February normals by Thursday. Following the passage of this system...the ECMWF and GEM build another large area of high pressure and plentiful dry air across our region Thursday night and Friday...while the GFS quickly tracks yet another southern stream system along the path of its predecessor and across our region. Given our continuity and that the latter solution remains an outlier...for now will continue to aim more optimistic and indicate the return of fair and mainly dry weather for the end of the week...along with continued near to slightly above normal temperatures. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... Cigs of 2500 to 3500 feet will be found across the majority of western and north central New York for the remainder of the pre dawn hours...with some light lake effect snow reducing vsbys to MVFR levels at times for the counties lining the south shore of Lake Ontario...including at KBUF. After daybreak...cigs will gradually climb to VFR levels for most of the region with the areas of light snow tapering off to flurries. The exception will be between KROC and KSYR where lower cigs from continued nuisance lake effect should persist. Tonight...high pressure arching southeast across the Lower Great Lakes will provide fair VFR weather across the majority of the region. Again...the exception will be close to Lake Ontario where some lake induced strato-cu will be found between 2500 and 3500 feet. Outlook... Sunday...VFR/MVFR with a chance of snow showers south of Lake Ontario. Monday...MVFR with a weak system moving across the region. Tuesday...VFR. Wednesday...MVFR with a chance of snow. && .MARINE... A relatively tight sfc pressure will remain in place over the Lower Great Lakes through at least midday...as a deep storm system will continue to move away via northern Quebec. This will keep small craft advisories in place for the nearshore waters of Lake Ontario...although the SCA for Lake Erie has been extended into the early morning hours. As we push through the morning into the midday...expansive high pressure over the Canadian prairies will arch southeast across all of the Great Lakes. This will allow winds and waves (in ice free areas) to gradually subside below small craft advisory levels for most of Lake Ontario. The exception will be from Hamlin Beach to Mexico Bay where waves will likely remain elevated into the evening hours. The large Canadian high pressure system will then promote relatively light winds and minimal waves later Saturday night into Sunday. As we progress deeper into Sunday and Sunday night...northeast winds will freshen...especially over Lake Ontario. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 8 AM EST this morning for LEZ040- 041. Small Craft Advisory until 9 PM EST this evening for LOZ043-044. Small Craft Advisory until 1 PM EST this afternoon for LOZ042-045. && $$ SYNOPSIS...RSH NEAR TERM...RSH SHORT TERM...JJR LONG TERM...JJR AVIATION...RSH MARINE...RSH

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