U.S. Severe Weather Forecast (Verwachte atmosferische convectie)

Day Three

acus01 kwns 260540 
Storm Prediction Center ac 260538 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1138 PM CST Sat Feb 25 2017 

Valid 261200z - 271200z 

..there is a marginal risk of severe thunderstorms across central 
and northeast Texas... 

Thunderstorms are expected to develop from central into northeast 
Texas Sunday evening. Large hail is possible with the strongest 


Late evening model guidance suggests a digging short-wave trough 
along the California coast will deamplify and eject east across the southern 
rockies Sunday as a strong 500mb speed Max translates into the 
southern High Plains after dark. While this feature is expected to 
weaken with time, a small pocket of height falls will overspread Texas 
during the evening hours and a notable low level jet should establish itself 
over East Texas enhancing warm advection across this region. 

Latest diagnostic data suggests boundary-layer air mass over the 
western Gulf basin is beginning to advance northward toward deep 
south Texas. As a result, a surface warm front will move inland across 
the coastal plain...extending from near Houston to north of Austin 
by 27/00z. Timing of the low-amplitude short wave and expected 
destabilization north of the warm front favor thunderstorm 
initiation near or just after 00z. Mid-level lapse rates should 
steepen during the evening as a pronounced thermal trough approaches 
the I-35 corridor late evening. Forecast soundings suggest MUCAPE 
in excess of 1000 j/kg with strong bulk shear through the cloud 
bearing layer. Given the expected large-scale ascent, due to warm 
advection, and thermodynamic environment, have introduced 5% severe 
probs for hail with the strongest updrafts. Thunderstorms will 
spread/develop into northeast Texas as the warm front lifts into this 
region of the state. 

..Pacific northwest... 

Strong mid-level short-wave trough will dig southeast across western 
Washington/or during the day1 period and very cold air aloft will overspread 
the Pacific northwest. 500mb temperatures should cool below -30c 
beneath the trough and lapse rates will steepen accordingly. While 
instability will be weak, shallow convection could attain heights 
necessary for lightning discharge given the cold profiles. Greatest 
risk for isolated thunderstorms will be during the first half of the 

.Darrow/picca.. 02/26/2017 


Mesoscale Discussion

acus11 kwns 252325 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 252324 

Mesoscale discussion 0214 
National Weather Service Storm Prediction Center Norman OK 
0524 PM CST Sat Feb 25 2017 

Areas affected...southeastern Vermont...southern New Hampshire...far southern 
ME...MA...eastern CT...and Rhode Island 

Concerning...severe potential...watch unlikely 

Valid 252324z - 260030z 

Probability of watch issuance...20 percent 

Summary...a watch downstream of Severe Thunderstorm Watch 40 is 
unlikely due to an unfavorable airmass. 

Discussion...radar imagery as of 2315z shows a bowing line of 
thunderstorms across the lower Hudson Valley of New York moving into the 
eastern part of Severe Thunderstorm Watch 40. These thunderstorms 
have recently (2244z) produced a measured severe wind gust of 69 mph 
at the Montgomery Airport in Orange County NY, along with some tree 
damage. As this convection continues eastward along a cold front 
into much of the remainder of New England, it is expected to quickly 
weaken due to a stable airmass. Southeasterly winds off the Atlantic 
across this region have prevented appreciable destabilization into 
much of Massachusetts/CT/RI/VT/NH, with rap mesoanalysis suggesting MUCAPE of 
100 j/kg or less downstream of the ongoing convection. While a very 
isolated strong to damaging wind threat may persist slightly to the 
east of the current Severe Thunderstorm Watch, downstream watch 
issuance is unlikely due to the hostile thermodynamic environment. 

.Gleason/guyer.. 02/25/2017 

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


Latitude...Lon 42797276 43677238 43627091 43257041 42537060 41367116 
41217269 42797276