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Area Forecast Discussion (AFD)

Issued by Hastings, NE (GID)

FXUS63 KGID 182327

Area Forecast Discussion
National Weather Service Hastings NE
627 PM CDT Wed Jul 18 2018

Issued at 626 PM CDT Wed Jul 18 2018

Just issued svr tstm watch 281 until 06Z. We cont to monitor tstms
upstream and it currently appears the best chance of tstms tonight
will be N of a line from ODX-GRI-JYR. We were generous with the
counties in the watch to the S and W of that area because some
CAMs suggest additional tstm development W of the on-going

We will cont to monitor the situation thru the evng...but for now
the highest risk for svr tstms in the next 2 hrs is over Valley 
and Greeley counties.


.SHORT TERM...(This evening through Thursday)
Issued at 248 PM CDT Wed Jul 18 2018

Focus of attention is on the wave moving through the
northern/central Plains tonight. As of now, subsidence behind
morning convection should keep us largely dry this afternoon and
early evening, but convection has already developed along an area
of low-level convergence in South Dakota and several models send
this convection to the south tonight. Not a lot of agreement among
short term models. For example, the NAMnest and NSSL WRF takes
convection as far west and south as our western CWA and north
central Kansas, whereas the HRRR barely clips us in our northeast.
There is enough uncertainty to include nearly our entire CWA with
at least a slight chance of thunderstorms, with higher chances in
our northeast.  

Since we've seen a lot of sky cover, this may hinder any
development here, but with strong bulk shear for July and MLCAPE
of over 1000 J/kg, there is enough support for thunderstorms to
propagate into our area. A tornado is not completely out of the
question in our north, considering our 0-1 km helicity above 50,
especially if the mode of convection will be discreet cells rather
than linear, which is still a bit of a question, even in the short
term. Confidence in this forecast is not all that high, as
numerical models in the short term have regularly failed over the 
past couple of days, and there is still a shortage of agreement 
and consistency among them.

.LONG TERM...(Thursday night through Wednesday)
Issued at 248 PM CDT Wed Jul 18 2018

Warm advection type showers are still on the table for late
Thursday night, and elevated instability and favorable mid-level
lapse rates could aid in giving us some marginally large hail and
severe wind gusts.

Although the subtropical ridge builds west into the Great Basin
stretching into the southern Plains, we will largely remain on 
the northeastern and eastern periphery which will make us 
vulnerable to a series of shortwave troughs, especially from the 
latter half of the weekend into next week.

Temperatures should be rather typical for summer, with highs in
the 80s and lower 90s and lows in the 60s for the most part.


.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 620 PM CDT Wed Jul 18 2018

Significant Wx: A brief IFR +TSRA possible tonight.

Tonight: VFR...but svr tstm watch #281 is in effect until 06Z.
Can't rule out a +TSRA with G50 kt. Outside of any tstms...SE
winds 10 kt or less will become VRB after 07Z. Confidence: Medium

Thu: VFR with a few CU forming around midday with bases lifting to
6-7K ft. NW winds 5-10 increasing to 10-20 kt. Confidence: High




SHORT TERM...Heinlein
LONG TERM...Heinlein