Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
841 FXUS61 KBUF 250005 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 805 PM EDT Tue Sep 24 2024 .SYNOPSIS... Low pressure will move across the Great Lakes tonight, spreading another round of rain across the region. A trailing front will move slowly across the area Wednesday through Wednesday night and support some additional rainfall. A few showers may linger Thursday, especially east of Lake Ontario. High pressure will then build into the Great Lakes region, bringing a return to mainly dry weather Friday through the weekend. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... Currently, a batch of steadier showers is moving into the north country from the northern Finger Lakes and Lake Ontario. A lighter more broken area of showers is across the Niagara Frontier to near Rochester, tracking northeast to Lake Ontario. Further upstream, additional showers with some thunderstorms is found over the western end of Lake Erie, tracking toward WNY, but guidance keeps most of this activity just to the west in Canada. A deep longwave trough will dig across the Great Lakes and Ohio Valley through Wednesday. Large scale forcing for ascent will increase ahead of this trough through tonight. This lift will be supported by DPVA, topped by mid/upper level diffluent flow, and deep moisture transported northward by a 40 knot southerly low level jet. Terrain influences will play an important role in coverage of rain and also rainfall amounts. Persistent south/southeast downslope flow will result in shadows of lower rainfall amounts and diminished rain coverage to the north of terrain and on the lake plains. For these areas rainfall totals will average a tenth to a quarter inch, with the greatest rainfall amounts east of Lake Ontario where around a half inch of rain is expected. Southerly downslope winds will continue Wednesday, and the lake plains may see a period of completely dry weather Wednesday morning due to a mid level dry slot and the drying influence of downslope flow. However, the frontal zone will remain draped from the Ohio Valley to Central NY, and this along with diurnal heating/instability will support an uptick in showers Wednesday afternoon. While there will not be much surface based instability during this event, there will be elevated instability which could support some thunderstorms embedded in heavier showers through Wednesday evening. The surface low will track to our north and into southern Quebec Wednesday night, with a trailing cold front moving across our region. This will bring another round of showers to the area, especially east of Lake Ontario which will be closer to the upper level trough. This will bring another half inch or so of rainfall to that region. During this time temperatures will average above normal, especially overnight lows. The lake plains will be the warmest locations due to warming from the southerly flow downsloping. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... By Thursday morning, the eastern Great Lakes will be sandwiched between two upper level closed lows: one centered over far southwestern Quebec, and another across the lower Mississippi Valley. As the northern trough translates eastward towards the Canadian Maritimes through Friday night, a flattening ridge of high pressure and mid-level dry air will crest over the southern trough and become wedged across the forecast area. This will allow the west- to-east drying trend to continue through the day Thursday. While the North Country will likely still be contending with showers and possibly a thunderstorm or two Thursday morning, much of WNY should already be drying out. Dry weather should then be found areawide from Thursday evening through at least Friday. Thereafter, much of the sensible weather forecast across our region will depend upon the evolution of the upper low over the Mississippi Valley. As TS Helene and its remnants tracks northward out of the Gulf of Mexico Thursday night, it is expected to rise along the eastern flank of the low and closely interact with the upper level system. The details on how exactly these features will interact remains a bit uncertain, though TS Helene`s northward momentum and how it rearranges the orientation of the southern branch of the jet stream is expected to allow its remnants to track northward towards the forecast area. At this juncture, the area of high pressure over the region is expected to block much of this tropical-based moisture, though additional showers reaching WNY by Friday night cannot be ruled out. Temperatures Thursday through Friday night are expected to remain above normal, with highs mainly in the 70s Thursday and Friday, a few 60s lingering on the hilltops. Lows Thursday and Friday nights will range from the upper 70s across the Tug/Western Dacks to the upper 60s closer to Lake Erie, with 50s elsewhere. && .LONG TERM /SATURDAY THROUGH TUESDAY/... The evolution of the upper low over the Mississippi Valley will be the large scale feature to watch during this period. As alluded to in the short term, this system will be interacting with TS Helene and its remnants late in the week, the details of which remain uncertain at this time. Ensemble systems show the ridge across the Great Lakes region remaining in place which should keep the forecast mostly dry, however there are some signals from the ensemble systems that draw the upper low further north and/or open the low into a trough across the forecast area. This could result in increasing moisture and therefore there are low chances of showers across the forecast area over the weekend and through early next week. Temperatures remain above normal through the period, with highs well into the 70s across the lower terrain each day and upper 60s/low 70s across the hilltops. Lows will mostly range in the 50s, though there could be a few upper 40s across the hilltops and low 60s near the lakeshores. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... An upper level trough will slowly dig across the Great Lakes through Wednesday. A round of steady rain showers with a few embedded thunderstorms will move from west to east across the area through tonight. Rain will be moderate at times, reducing vsby to MVFR. Cigs will vary, with southerly downslope flow helping to keep the lake plains mainly VFR/MVFR despite the rain. This includes KBUF/KIAG/KROC/KART. Mainly IFR cigs at KJHW, with fog possible tonight. Expect a break in the showers for most locations Wednesday morning as a LLJ exits to the east. However, showers and a few thunderstorms will expand in coverage Wednesday afternoon due to diurnal heating, especially from the Genesee River valley eastward. Outlook... Wednesday night...MVFR/IFR with showers likely. A few widely scattered thunderstorms possible. Thursday...MVFR east of Lake Ontario with a chance of showers. Becoming mainly VFR elsewhere. Friday through Sunday...Mainly VFR. Local IFR in valley fog across the Southern Tier possible overnight into the morning. && .MARINE... A moderate pressure gradient will remain in place over the eastern Great Lakes through Wednesday between persistent high pressure over the Canadian Maritimes and low pressure moving through the central Great Lakes. This will maintain moderate southeasterly flow through Wednesday, with the strongest winds on the east half of Lake Ontario tonight through Wednesday. The southeast wind direction will continue to push the greater wave action into Canadian waters, but the offshore winds will become strong enough to require a Small Craft advisory for the eastern ends of Lake Ontario and Lake Erie. Winds will gradually become southwest and then west Wednesday night through Thursday as a trough crosses the eastern Great Lakes from west to east, with wind speeds decreasing with the passage of the trough. Northeast flow will then pick up Friday, possibly requiring small craft headlines on Lake Erie and western Lake Ontario. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 8 AM EDT Wednesday for LEZ040-041. Small Craft Advisory until 2 AM EDT Thursday for LOZ045. && $$ SYNOPSIS...Apffel/Hitchcock NEAR TERM...Apffel/Hitchcock/SW SHORT TERM...PP LONG TERM...HSK/PP AVIATION...Apffel MARINE...Apffel/Hitchcock