Grand Island, NY Weather

What Has Changed

Minor changes to the forecast with this update.

Key Messages

1) Dry weather is expected during the majority of this week. However, periodic rain showers are expected in North-Central NY later this morning into this afternoon. Periodic rain showers are possible region-wide this Thursday night into Friday morning.

Discussion

KEY MESSAGE 1...Dry weather is expected during the majority of this week. However, periodic rain showers are expected in North-Central NY later this morning into this afternoon. Periodic rain showers are possible region-wide this Thursday night into Friday morning.

W'erly to WNW'erly flow aloft and embedded shortwave troughs impact our region today. Variable amounts of low/mid/upper-level cloudiness are expected amidst moist isentropic ascent ahead of the shortwave trough axes. At the surface, a ridge exits generally SE'ward and will be followed by the SE'ward passage of a weak cold front during the late morning through early afternoon. A rather dry atmospheric column at/near the surface should permit a dry cold front passage across most of our CWA. However, forcing for ascent along the front should coincide with sufficient low-level moisture and permit the development of isolated to scattered and light rain showers across North-Central NY late this morning through afternoon. Behind the front, another high pressure ridge builds from central Canada and vicinity. Afternoon highs should reach mainly the mid 50's to mid 60's.

During tonight through Tuesday night, the surface ridge will continue to affect our region as the embedded high pressure center moves from northern ON toward northern New England, while the ridge aloft builds from the Upper Midwest to the eastern Great Lakes. Dry weather is expected as stabilizing subsidence accompanies the ridge. Low-level CAA behind the above-mentioned cold front passage will allow a sufficiently-cold mean low-level flow over/downwind of the ~15C to ~16C eastern Great Lakes to yield weak lake-induced instability amidst scarce synoptic-scale low-level moisture late this afternoon into tonight. Scattered to widespread lake-effect and upslope stratocumuli are expected to affect much of Western and Central NY as the mean low-level flow veers from NW'erly to NE'erly and results in a period of upslope flow along the higher terrain in our CWA. Any lingering lake-effect and upslope stratocumuli are expected to dissipate by late Tuesday morning amidst the stabilizing subsidence and low-level dry air advection that will accompany the aforementioned ridge. The stratocumuli are expected to be too shallow to produce precip. Lows should reach mainly the lower 20's to mid 30's around daybreak Tuesday and highs should reach the mid 40's to lower 60's late Tuesday afternoon as low-level CAA persists. Weak or calm surface winds, low humidity, and sufficient cloud breaks, especially farther east, are expected to permit appreciable radiational cooling very late Tuesday afternoon through daybreak Wednesday, when lows should reach mainly the lower 20's to lower 30's in North-Central NY, the lower to mid 30's in our Finger Lakes counties, and the 30's to lower 40's in our eight western-most counties.

On Wednesday through Wednesday night, the ridge at the surface and aloft should exit E'ward and allow a warm front starved of low-level moisture to sweep NE'ward through our region and usher-in a somewhat warmer air mass. Fair weather is expected to persist. Late afternoon highs should reach the 50's to lower 60's in North-Central NY and the upper 50's to upper 60's elsewhere in our CWA. Thereafter, overnight lows should reach the mid 30's to mid 40's in North-Central NY and the lower 40's to lower 50's elsewhere in our CWA around daybreak Thursday. Note: Sufficient cloud breaks and weak or calm surface winds should contribute to localized steam fog in the Black River Valley during the predawn hours through about 10 AM EDT today through Wednesday, respectively, and in the inland lake and river valleys of the Western Southern Tier and Finger Lakes Region during the same time period today and tomorrow, respectively.

W'erly to WNW'erly flow aloft and a series of attendant troughs and ridges at the surface and aloft should affect our region this Thursday through Saturday. Current odds favor primarily dry weather as ridging should affect Western and Central NY during the majority of the time period. However, a weak cold front should sweep E'ward through our region Thursday night. Periodic rain showers are possible along and ahead of this front Thursday night due to moist isentropic ascent ahead of a shortwave trough axis aloft and low-level convergence/ascent along the front coinciding with sufficient low-level moisture. Unusually-mild weather for late October is expected courtesy of largely zonal flow aloft.

Aviation

Variable amounts of low/mid/upper-level cloudiness affect Western and Central NY through 06Z/Tues as disturbances embedded in W'erly to NW'erly flow aloft impact our area. At the surface, a ridge exits SE'ward before a cold front sweeps SE'ward through our region between ~13Z and ~17Z/Mon. Behind the front, another ridge builds from central Canada and vicinity through 06Z/Tues. The cold front passage will cause our regional surface winds around 5 to 10 knots to veer from SW'erly to NW'erly. Behind the front, NW'erly surface winds around 5 to 10 knots veer to NE'erly in response to the building ridge.

Limited moisture at/near the surface is expected to result in a dry cold front passage across most of our area. However, periodic rain showers with VFR visibility and MVFR ceilings should impact North-Central NY late this morning through afternoon as the cold front at the surface and aloft sweeps through. Behind the front, scattered to widespread stratocumuli with bases near 2kft to 3.5kft AGL are expected to develop during the late afternoon or early evening and then persist through 06Z/Tues as mean low-level flow veers from NW'erly to NE'erly, modest lake-induced instability develops over the eastern Great Lakes, and a period of upslope flow develops along the higher terrain in our area.

Note: Sufficient cloud breaks and weak surface winds should contribute to localized steam fog with MVFR to LIFR in the inland river and lake valleys of the Western Southern Tier, Finger Lakes Region, and North-Central NY through ~14Z/Mon and again from ~03Z/Tues through 06Z/Tues.

Outlook...

Tuesday through Wednesday...Dry weather and mainly VFR expected. Lingering stratocumuli and associated borderline VFR/MVFR ceilings should dissipate by late Tuesday morning. In addition, localized fog with MVFR or worse is expected in inland river and lake valleys each late evening through mid-morning in the Western Southern Tier, Finger Lakes Region, and North-Central NY.

Wednesday night through Friday...Dry weather and mainly VFR expected. However, periodic rain showers with MVFR are possible Thursday night into Friday morning.