U.S. Severe Weather Forecast (Convective Outlook)

Day Three

acus01 kwns 260550 
Storm Prediction Center ac 260549 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1249 am CDT Fri Apr 26 2019 

Valid 261200z - 271200z 

..there is a slight risk of severe thunderstorms from NC to the 
middle Atlantic... 

Thunderstorms capable of producing damaging wind and a few tornadoes 
are expected from North Carolina into the middle Atlantic Friday. 
Isolated damaging wind gusts are also possible over northern Utah, 
southeast Idaho, southwest Wyoming and northwest Colorado. Other 
storms may produce a few strong wind gusts over a portion of the 
Florida Peninsula. 

..NC to the middle Atlantic... 

Strong 500mb jet is forecast to dig southeast across MO into the Tennessee 
Valley region early in the period before shifting into the Lee of 
the southern Appalachians Friday afternoon. In response, strong 12hr 
500mb height falls will develop across the middle Atlantic region 
and a pronounced surface front will surge east of the higher terrain 
shortly after 18z. While low-level moisture is not particularly high 
across this area this morning, lower 60s surface dew points are 
expected to advance north across the Delmarva into southeast PA 
ahead of the wind shift. Latest model guidance suggests 
surface-based buoyancy will develop by 16-17z as temperatures warm 
through the upper 60s to near 70f. Additionally, strongly diffluent 
flow aloft suggests favorable venting for convection within 
aforementioned region of large-scale forcing for ascent. 

Current thinking is scattered thunderstorms will develop ahead of 
the approaching short wave during the morning then convection should 
intensify as forcing encourages upscale growth. Strongly sheared 
profiles favor rotating storms and there is some concern for a few 
tornadic supercells, especially across the Delmarva into southeast 
PA where low-level flow will be more backed. Latest cams support 
this scenario and severe probs will be nudged north a bit to reflect 
this threat farther north across the middle Atlantic. 

..central rockies... 

Strong mid-level short-wave trough is forecast to dig southeast 
across the northern inter-mountain region during the day. As a 
result, frontal forcing will be maximized during the afternoon along 
a corridor from northern Utah into northwest Colorado. Convection is 
expected to readily develop ahead of the front within a steep 
lapse-rate environment, though precipitable water values are not expected to be that 
high. Relatively low sub-cloud relative humidity should contribute to gusty 
downdrafts within the stronger storms. Convection may loosely 
organize ahead of the front as deep-layer shear will prove conducive 
for sustained updrafts. 

.Darrow/Gleason.. 04/26/2019 


Mesoscale Discussion

acus11 kwns 260337 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 260337 

Mesoscale discussion 0450 
National Weather Service Storm Prediction Center Norman OK 
1037 PM CDT Thu Apr 25 2019 

Areas affected...Florida Big Bend vicinity 

Concerning...severe potential...watch unlikely 

Valid 260337z - 260430z 

Probability of watch issuance...20 percent 

Summary...isolated damaging gusts are possible with the approaching 
squall line. The need for an additional watch is uncertain but 

Discussion...radar mosaic shows a well-organized squall line over 
the northeast Gulf of Mexico moving east towards the Florida Big Bend. 
The airmass over this region has moistened with upper 60s surface 
dewpoints but the 00z tbw and tlh raobs showed poor lapse rate 
profiles. Ample deep-layer shear is present as strong southwesterly 
flow associated with a mid-level impulse over the central Gulf 
coastal states. As such, the squall line will likely maintain 
sufficient organization for a risk for isolated damaging gusts. The 
overall magnitude and expected coverage of the severe threat will 
likely preclude an additional watch being issued over North Florida. 

.Smith/grams.. 04/26/2019 

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


Latitude...Lon 30008282 29388216 28838217 28768272 29058282 30038393 
30238371 30008282