U.S. Severe Weather Forecast (Ionchas Comhiomprach)

An Tríú Lá

acus01 kwns 151248 
Storm Prediction Center ac 151246 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0646 am CST Fri Dec 15 2017 

Valid 151300z - 161200z 

..no thunderstorm areas forecast... 

thunderstorm threat is too small for an outlook area through 

In mid/upper levels, a split-flow pattern with gradual large-scale 
deamplification is expected through the period, as a trough now 
offshore from the Pacific northwest penetrates the mean West Coast 
ridge and amplifies inland. By 12z, that trough should extend from 
the British Columbia rockies southward to the Sierra then southwestward offshore 
from Southern California. This will lead to the late-period and day-2 
ejection of a presently cut-off cyclone now located over 
northwestern mx and adjacent waters. Meanwhile, a positively tilted 
shortwave trough and related vorticity ribbon will eject eastward 
from its present position over the lower Ohio Valley, Ozarks and 
Southern Plains. 

At the surface, a cold front was analyzed from a weak low over SC 
southwestward across the north-central Gulf to another weak 
frontal-wave low over the Gulf east of bro, then southwestward to 
eastern mx. The front should proceed southeastward today and 
tonight, reaching south-central Florida and the central/southwestern 
Gulf. Any suitable vertical juxtaposition of favorable low-level 
Theta-E with lapse rates aloft to support thunderstorms should 
remain south of that front, and well offshore from the contiguous 
U.S., Whether over the Gulf or Atlantic. 

.Edwards.. 12/15/2017 


Mesoscale Discussion

acus11 kwns 120330 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 120330 

Mesoscale discussion 1795 
National Weather Service Storm Prediction Center Norman OK 
0930 PM CST Mon Dec 11 2017 

Areas affected...central New York 

Concerning...heavy snow 

Valid 120330z - 120930z 

Summary...snowfall rates will increase gradually through 06-09z, 
with peak rates likely to exceed 1 inch per hour from about 07-12z. 

Discussion...in association with a midlevel shortwave trough 
approaching the upper Ohio Valley, a deformation snow band has been 
developing eastward over Lake Erie. Low-midlevel warm 
advection/ascent in advance of the trough, as well as weak 
frontogenesis, will support additional eastward expansion of the 
snow band across central New York through the early morning hours. 
Top-down saturation of the column is just beginning across western 
into central NY, and snowfall rates will increase as column 
saturation develops eastward and forcing for ascent increases 
through the early morning hours. Peak snowfall rates should 
approach or exceed 1 inch per hour, and may persist for 3-6 hours at 
locations within the expected corridor of the snow band. 

.Thompson.. 12/12/2017 

..please see www.Spc.NOAA.Gov for graphic product... 


Latitude...Lon 43217361 43007412 42747497 42497608 42457687 42517744 
42667771 43037760 43837544 44037419 43947361 43617347