243 
FXUS63 KGID 200520
AFDGID

AREA FORECAST DISCUSSION
National Weather Service Hastings NE
1120 PM CST Thu Nov 19 2020

...Aviation Update...

.DISCUSSION...(This evening through Thursday)
Issued at 254 PM CST Thu Nov 19 2020

Shaping up to be a really nice day today with highs well above 
average for this time of year. In fact, highs are actually over 
achieving in a few places so far, so adjustments were made as 
needed. The passage of a sfc trof along with a rather diffuse cold 
front this morning has turned our winds northerly for today with 
speeds generally less than 15 mph. Cooler, more seasonable weather 
is on its way back after today. Though we are expected to remain in 
rather zonal flow aloft the next couple of days, there will be a 
couple shortwave trofs that are expected to roll through over the 
next 7 days. Those two trofs and their associated precip chances is 
what I'd like to focus the rest of this discussion on. 

Shortwave 1, Saturday: 

This first wave has been increasingly becoming less of a concern for 
our area with each new model run it seems. A weak midlevel trof is 
expected to swing through on Saturday ahead of its upper level 
counterpart, and possibly bring a slight chance for some precip. 
Currently not too confident regarding PoPs Sat-Sun early morning. 
Overall there is not a whole lot of forcing or moisture. The GFS 
has pushed this system further south with each run, the ECMWF has 
some weak QPF signal Saturday night, and the European ensembles 
only have a few members showing measurable precip. Of the hi-res 
models, only the NAM and NAMNEST are run far enough out to capture
Saturday at this point. The NAM keeps nearly all the QPF to our 
south, and the NAMNEST, unsurprisingly, has the strongest QPF 
signal for us. Wouldn't be surprised if the NBM decreases PoPs a 
good bit over the next several runs as the short term hi-res 
models make their way into the solution.

Shortwave 2, Tuesday: 

Brief ridging aloft is expected Sunday night into Monday in the wake 
of the first wave mentioned above. Monday afternoon/evening a minor 
perturbation ahead of the next approaching trof looks to pass 
overhead, coinciding with the leading edge of the mid-level trof 
(ahead of the main upper level trof). As a sfc low develops just to 
the east of the Rockies expect to see a tightening of the sfc 
pressure gradient and therefore gusty southerly winds for Monday. 
PoPs will gradually begin to increase starting as early Monday 
afternoon, as the system as a whole moves east and the sfc low 
pushes off the Rockies. Currently the ECMWF has the upper level trof 
deepening as it crosses the Rockies and shows the sfc low deepening 
and centered over northern OK and into southern KS with a broad 
precip shield extending north and northeast. The GFS shows a faster 
and more progressive system with the upper level trof not deepening 
until over the Plains on Tuesday. With the upper level trof not 
deepening as early/further west, the associated sfc low ends up much 
farther north and is instead centered over central NE Monday night. 
These differences in progression lead to a wide disparity in both 
spacial and temporal coverage of precip. The ECMWF has the majority 
of QPF Tuesday afternoon into the overnight. The GFS on the other 
hand has the majority of QPF Monday evening and overnight into 
Tuesday morning. This could be a key difference to watch especially 
with regards to potential precip type. Once this second wave passes, 
we return to zonal flow aloft for a few days. 

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Saturday)
Issued at 1115 PM CST Thu Nov 19 2020

VFR conditions are expected through the TAF period. A cold front
has just crossed KEAR and KGRI, bringing a wind shift to the
northwest and an increase in wind speeds. Surface high pressure
will build southeast from the Dakotas today/tonight with overall
wind speeds relatively light. 

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.

&&

$$

DISCUSSION...Shawkey
AVIATION...Fay