U.S. Severe Weather Forecast (Przegląd konwekcyjny)

Day Three

acus01 kwns 170553 
Storm Prediction Center ac 170552 

Day 1 convective outlook 
National Weather Service Storm Prediction Center Norman OK 
1152 PM CST Mon Jan 16 2017 

Valid 171200z - 181200z 

..there is a marginal risk of severe thunderstorms across portions 
of south Texas... 

A few severe thunderstorms may affect portions of south Texas today 
and tonight. 

An upper cyclone is forecast to track from portions of the Gulf of 
California and northwest Mexico to the vicinity of northeastern nm 
and the Texas Panhandle. A band of enhanced midlevel southwesterly flow 
will extend over TX, being reinforced by the progression of a 
moderate speed maximum attendant to the cyclone. In response to 
these developments, modest low-level warm advection will persist 
through the period across a portion of the south-central states, 
while a surface frontal zone extends from the lower MS valley to 
south Texas. 

..portions of south Texas... 
Persistent low-level warm advection will support thunderstorm 
potential on the cool side of the boundary through the day and into 
the overnight hours. Sufficient vertical shear beneath the enhanced 
midlevel southwesterly flow (effective bulk shear around 35 to 50 
kt), amid moderate midlevel lapse rates and ample high-level 
venting, will support an isolated, marginally severe hail risk with 
elevated convection north of the boundary. 

For this evening into tonight, a slight boost in deep ascent 
peripheral to the Mobile cyclone may offer some near-surface-based 
convective potential, near and on the warm side of the frontal 
zone -- especially across portions of the Texas coast. Relatively rich 
low-level moisture was sampled by the Corpus Christi and Brownsville 
Monday evening soundings, with mean mixing ratios around 13.2-13.4 
g/kg. Similar rich moisture should persist into tonight. Sufficient 
deep shear, with curved low-level hodographs, may support organized 
convection capable of isolated instances of all severe hazards. 

The overall compact nature of stronger mid-level height falls 
tracking well to the west/northwest of Richer low-level moisture, 
and the only modest low-level mass response to the Mobile cyclone, 
and anticipated cluster-type convective Mode, should tend to 
marginalize the overall severe risk. 

.Cohen/Dean.. 01/17/2017 


Mesoscale Discussion

acus11 kwns 170037 
sels mesoscale discussion 
Storm Prediction Center mesoscale discussion 170036 

Mesoscale discussion 0063 
National Weather Service Storm Prediction Center Norman OK 
0636 PM CST Mon Jan 16 2017 

Areas affected...central and northern lower Michigan 

Concerning...freezing rain 

Valid 170036z - 170630z 

Summary...precipitation rates are expected to slowly increase this 
evening as temperatures mostly remain below freezing. An initial mix 
of precipitation is expected to transition to mostly freezing rain 
by late tonight, with rates up to 0.05 inches per hour possible. 

Discussion...at 0030z, a shield of precipitation is slowly advancing 
northward across lower Michigan in advance of an upper trough and 
associated low pressure system moving out of the Central Plains. 
Substantial dry air in the lower half of the troposphere, evident on 
the 00z apx sounding, has limited precipitation rates thus far, but 
continued moistening will eventually lead to some increase in 
precipitation rates this evening as ascent continues within the 
warm-conveyor belt. 

An initial mix of precipitation types is expected early this 
evening, especially with northward extent, given a relatively weak 
warm nose and potential for some evaporative cooling of the column 
before saturation is achieved. Continued warm advection should 
result in a strengthening warm nose and erosion of the subfreezing 
layer near the surface, resulting in a transition to primarily 
freezing rain by later this evening. Surface temperatures will be 
somewhat marginal, especially across the southern part of the mesoscale discussion 
area, and a slow northward progression of the surface freezing line 
will occur as weak but persistent warm advection continues, with an 
eventual transition from freezing rain to rain possible from south 
to north during the overnight hours. 

.Dean.. 01/17/2017 

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


Latitude...Lon 43298610 43498644 44038644 44488615 44748606 45068565 
45028517 45008466 44758396 44478346 43958308 43588291 
43278323 43098373 43048427 43058512 43298610