U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 231957 
Storm Prediction Center ac 231956 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
0156 PM CST Tue Jan 23 2018 

Valid 232000z - 241200z 

..no severe thunderstorm areas forecast... 

isolated thunderstorms will remain possible across parts of the 
mid-Atlantic, southern New England, and the southern Florida 
Peninsula through early evening. 

No notable changes have been made to the ongoing forecast, other 
than focusing the northern general-thunder area close to the coast, 
where sufficient, albeit weak, buoyancy remains for isolated 
thunderstorms (prior to further veering of winds and drying in low 

A narrow, shallow band of thunderstorms has developed downwind of 
Lake Ontario this afternoon, on the nose of strong mid-level ascent 
ahead of a robust vorticity maximum crossing western New York. A few 
further strikes may occur downstream, but meager elevated buoyancy 
will likely preclude a greater coverage of thunderstorms, and no 
general-thunder area is introduced. 

.Picca.. 01/23/2018 

Previous discussion... /issued 1019 am CST Tue Jan 23 2018/ 

..mid Atlantic through early afternoon... 
A pronounced midlevel trough will move over the lower Great Lakes 
today and northern New England tonight, as an associated surface 
cold front progresses off the Atlantic coast later today through 
tonight. The mid-upper jet core will cross the mid Atlantic region 
today, with the stronger height falls and deeper ascent expected to 
remain northeast of inland areas. Regional vwps show that low-level 
flow has trended to more unidirectional/southwesterly with straight 
hodographs, consistent with diminished warm advection. Thus, only 
shallow/weak ascent is expected along segments of the synoptic cold 
front which will move east of the Appalachians today, with gradual 
low-level drying expected from west-east through early afternoon 
across VA/NC. The threat for damaging winds appears to be too low 
the remainder of the period to warrant maintaining an outlook area. 

..Southeast Florida this afternoon... 
Isolated thunderstorms will be possible across Southeast Florida in 
association with low-level moistening, differential surface heating, 
and local sea breeze circulations. 


Mesoscale Discussion

acus11 kwns 231104 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 231103 

Mesoscale discussion 0045 
National Weather Service Storm Prediction Center Norman OK 
0503 am CST Tue Jan 23 2018 

Areas affected...northern Maine 

Concerning...winter mixed precipitation 

Valid 231103z - 231500z 

Summary...heavy snowfall with rates of up to 1 inch per hour will be 
possible across northern Maine over the next 3 to 4 hours. A mix of 
snow, freezing rain and sleet is likely after daybreak from near 
Caribou westward to the Canadian border. 

Discussion...the latest water vapor imagery shows a strong 
upper-level system from the Great Lakes southward into the Ohio and 
Tennessee valleys. Southwest anticyclonic flow exists ahead of the 
system across the northeast. A plume of low to mid-level moisture 
was moving across New England with a vorticity Max analyzed by the 
rap in far western Maine near the Maine-Canadian border. In 
addition, the exit region of a 50 to 60 kt low-level jet is analyzed 
over northern New England. These factors along with backed easterly 
low-level flow is contributing to strong isentropic ascent across 
northern Maine favorable for heavy snow. The greatest potential for 
heavy snow will be from Caribou, ME and Edmundston, Canada westward 
to the Canadian border where snowfall rates could reach 1 inch per 

Further south, the core of a strong low-level jet will result in 
considerable warming around 850 mb in central and northern Maine 
this morning. As a result of the related melting-layer depth 
increase, snowfall should become mixed with freezing rain and sleet 
after daybreak. This changeover should gradually progress northward 
across north-central Maine this morning. 

.Broyles/Edwards.. 01/23/2018 

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


Latitude...Lon 47496841 47576922 46767004 46177016 45996804 46306754 
47126770 47496841