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Area Forecast Discussion (AFD)

Issued by Buffalo, NY (BUF)

                            
000
FXUS61 KBUF 231552
AFDBUF

Area Forecast Discussion
National Weather Service Buffalo NY
1152 AM EDT Tue Jul 23 2019

.SYNOPSIS...
Sprawling high pressure over the Northern Plains will nose east 
across the Lower Great Lakes, while slowly drifting southeast to the 
mid Mississippi Valley by Wednesday. This will result in mainly dry 
weather across our region. Aside from a few isolated inland showers 
each afternoon, expect plentiful sunshine and comfortable conditions 
for through Wednesday. A warming trend can then be expected for the 
second half of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
We can expect a nice afternoon across the majority of the 
region...as expansive high pressure based over the center of the 
country will nose as far east as the Lower Great Lakes. Meanwhile... 
a cyclonic flow in the mid and upper levels will keep a feed of 
relatively cool comfortable air in place. The only problem with the 
latter is that with H85 temps in the vcnty of 10c...our convective 
temps will be around 22c. Many sites have already reached these 
values...and this is clearly seen by the expanding Cu field in 
visible imagery. While there will be some 'shadowing' over the 
counties lining the south shores of the lakes...its not out of the 
question that some of the inland Cu could support a brief shower.
Otherwise...it will be a great day to be outdoors as highs within a 
few degrees of 75 will be accompanied by low humidity. 

Fair weather will remain in place for the bulk of the region 
tonight...as the large surface high will continue to extend across 
the Lower Great Lakes. The only potential problem will be the slight 
chance for late night showers southeast of both lakes. Marginal lake 
induced instability from H85 temps arnd 10c will support this 
nominal risk. It will once again be a fairly comfortable night for 
sleeping with mins generally ranging from the lower 50s across the 
Southern Tier and Lewis county...to 55 to 60 elsewhere.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A weak mid level trough axis will slowly cross the eastern Great 
Lakes Wednesday. This system will have little deep moisture to work 
with, and very little in the way of low level features. Weak forcing 
from DPVA along with relatively cool mid level temperatures and 
associated modest lapse rates may allow for a few isolated showers 
to develop with the trough axis. These may occur on the lake plains 
in the morning, but will then focus well inland from the lakes by 
afternoon as stable lake shadows develop and spread inland. Coverage 
will be very spotty, with most areas remaining dry. 850mb temps 
around +10C will support highs in the mid to upper 70s at lower 
elevations and lower 70s on the hills.

Any isolated showers will end Wednesday evening as the weak mid 
level trough exits. This will leave mainly clear to partly cloudy 
skies overnight. The airmass remains fairly cool, with lows in the 
upper 50s to lower 60s on the lake plains and some lower 50s in the 
cooler Southern Tier valleys and Lewis County. 

A similar scenario will unfold Thursday as another weak mid level 
trough axis embedded in northwest flow aloft crosses the eastern 
Great Lakes. Weak forcing from this may support a few isolated 
showers, with any showers focusing inland away from the lakes in the 
afternoon as stable lake shadows develop. There may be enough 
instability by afternoon to support an isolated thunderstorm as 
well, but again the majority of the area will stay dry. Warm 
advection will allow temperatures to move back to around average, 
with lower 80s at lower elevations and mid to upper 70s for higher 
terrain.

Any isolated showers will end Thursday evening, leaving dry weather 
overnight. Ongoing weak warm advection and somewhat higher dewpoints 
will keep temperatures a little warmer. Expect lows to range from 
the mid 60s near the lakes to the mid 50s in the Southern Tier 
valleys and Lewis County.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A typical mid summer pattern will take shape Friday through early 
next week, with zonal flow confined mainly to along and north of the 
Canadian border, with a dominant upper level ridge across the 
southern U.S. extending into the Ohio Valley and Mid Atlantic. The 
bulk of the more organized rain chances will stay north and west of 
our region Friday through early next week in closer proximity to the 
westerlies and better forcing. The vast majority of the time will be 
rain free in our area, although a few isolated to widely scattered 
showers and storms cannot be ruled out, mainly in the afternoon and 
inland from the lakes. A southwest flow through the period will 
likely produce sizable stable lake shadows that will reduce or 
eliminate the chance for convection across most of the lake plains.

Temperatures will continue to creep upward with day to day warming 
beneath the building ridge. Expect highs to reach the mid 80s at 
lower elevations by Friday, and then mid to upper 80s at lower 
elevations Saturday through early next week. Humidity will also 
creep up with dewpoints rising into the mid to upper 60s over the 
weekend.

&&

.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
While some MVFR cigs will persist until 16z across parts of the Srn 
Tier...VFR conditions with light winds can be expected through this 
evening.

The fair flying weather will persist tonight...although late night 
fog and stratus over the Southern Tier could lead to another round 
of IFR conditions for KJHW and KELZ.

Outlook... 

Wednesday through Saturday...Mainly VFR.

&&

.MARINE...
While a weak surface pressure gradient will keep nearly ideal 
conditions (generally light winds and negligible waves) in place for 
recreational boating for the bulk of this week...there will be the 
risk for waterspouts later tonight and early Wednesday morning. 

The axis of a longwave trough will cross Lake Erie during the second 
half of tonight. Several of the WV channels depict subtle shortwaves 
within the trough. These features will move from the Upper Great 
lakes to Lake Erie tonight...with the focus being on the western 
half of the lake. NWS KCLE is already highlighting the risk for
spouts on their end of the lake. The aforementioned synoptic pattern
will be accompanied by a favorable thermal profile...as H85 temps
in the vcnty of 10-11C and lake surface temps around 25c will 
promote sufficient low level instability. As outlined by the 
outstanding waterspout research from Szilagyi (Environ Can)... 
this instability combined with a convective depth of more than 
15k ft is conducive for spout development. This will especially 
be the case in a regime with light winds and possibly a land breeze
boundary for which to focus low level convergence. Will thus 
add slight chc for spouts on Lake Erie from about 06 to 12z Wednesday.

&&

.BUF WATCHES/WARNINGS/ADVISORIES...
NY...None.
MARINE...None.

&&

$$

SYNOPSIS...JM
NEAR TERM...RSH
SHORT TERM...Hitchcock
LONG TERM...Hitchcock
AVIATION...RSH
MARINE...RSH