Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 281803
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
103 PM CDT THU JUL 28 2016

.UPDATE...
Issued at 958 AM CDT Thu Jul 28 2016

The first of potentially several updates to today`s forecast has
been published. Here are a few comments regarding mainly these
next 12 hours or so...

By far the main focus has been to considerably-increase chances of
at least light measurable rain (PoPs) for the late morning hours
in our western counties as the fairly weak cluster of
showers/storms drifting east-southeast from western NE is nearly
on our door-step. There is quite a bit of uncertainty whether
this rain will even get into any areas east of Highway 281 this
morning, but will at least carry some slight chances to there and
slightly east. This afternoon, unfortunately, is still a bit of a
"mystery" in both the PoP and severe weather department, as
several models are already off to a pretty "iffy" start with
regards to the ongoing morning activity. There are obviously
additional upstream disturbances lurking behind this first one (as
evidenced by convection over the NE/SD/WY border area, and as this
activity moves in later today the environment could be more
supportive of severe storms. That being said, the considerable
cloud cover associated with the first round of convection may not
do destabilization any favors. Taking the latest RAP13 at face
value, mixed layer CAPE/instability values this afternoon/early
evening are not exactly "off the charts" for our CWA, ranging from
only a few hundred J/kg in our northeast, to perhaps as much as
1000-1500 J/kg in our far west/southwest. Obviously with
seasonably-decent deep layer shear of at least 30-40 knots, at
least a few severe storms are certainly possible within our CWA
especially between the usual 3PM-10PM time frame. The majority of
the CWA is in either a Marginal/Slight Risk per the latest 13z SPC
Day 1 outlook so it`s tough to completely rule out a severe storm
anywhere (except for roughly the northeast 1/4), but in theory/"on
paper" agree that the overall-most widespread threat still looks
to focus slightly off to the southwest of our CWA where the
current Enhanced Risk is advertised.

Temp-wise, high temps could be a bit tricky today thanks to
varying periods of mostly sunny and cloudy/mostly cloudy, not to
mention the rain affecting at least our west part of the day. Made
some very minor downward tweaks to previous forecast, but will
maintain an expectation of generally low-80s in most Neb zones and
more-so mid-upper 80s in KS zones.

&&

.SHORT TERM...(Today and tonight)
Issued at 400 AM CDT Thu Jul 28 2016

Current radar shows thunderstorms mostly to the southwest of the
forecast area. With the current track, most of them should remain to
the west of the forecast area. Satellite and observations show mid
and high clouds across the area.

Through daybreak there could be a few of the thunderstorms that make
their way into the western part of the forecast area, but these
should be mainly isolated.

Northwest flow continues across the area today and tonight. There are
a couple of waves that move through the area. The first wave moves
into the area this morning. Thunderstorm chances spread into the
forecast area later in the morning and across much of the area
during the afternoon. Even with the upper level wave moving in,
there are still some differences in where and when the precipitation
will be. There is still enough of the models that bring something
into the area that have kept POPs fairly high. The best chance will
be in the southwest part of the forecast area. During the afternoon,
the MUCAPE is over 3000 J/KG, mainly in the west and southwest. This
is where the best chance of severe weather this afternoon and
evening. Have kept thunderstorms going into the overnight hours, but
as there is much less CAPE, the thunderstorms should not be
severe.

.LONG TERM...(Friday through Wednesday)
Issued at 400 AM CDT Thu Jul 28 2016

The biggest challenge will be determining any precipitation chances.

Northwest flow becomes more zonal over time as a subtropical ridge
builds north again. This will mean a direction toward warmer and
drier conditions heading into next week. However, there is a small
chance of precipitation through the end of the week, before the
ridge becomes stronger. And even for next week, we are not
completely guaranteed dry conditions as rogue waves may be able to
break through the ridge. Highs will warm from near 80 Friday when
sky cover from an early morning MCS may be stubborn to erode, into
the mid 90s by Monday. Severe weather is not exactly ruled out in
this period, but shear will become relatively low with weak steering
expected, and instability will be rather modest for this time of
year, except when dewpoints may creep up next week. We may even need
to pay attention to heat index next week if we get enough moisture
return.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Friday afternoon)
Issued at 103 PM CDT Thu Jul 28 2016

Although confidence is high that the MAJORITY of the period will
feature VFR ceiling/visibility and rain/storm-free conditions,
there is plenty of uncertainty in the finer details...as there
could easily be at least brief periods of sub-VFR and also
passing showers/storms.

Going into some of these details:
Starting with precipitation/storm chances, have focused a generic
"vicinity thunderstorm" (VCTS) mention during the mid-afternoon
through mid-evening hours to capture the most favored time frame
for possible convection, but it`s not out of the question that
some activity could affect the terminals both slightly before and
also after this specified time. Confidence in timing is still too
low to go with any TEMPO groups so stay tuned for amendments if
these become necessary. Turning to ceiling, confidence is pretty
high in VFR especially the first 6-12 hours (unless convection
lowers briefly), but model guidance varies quite a bit on ceiling
potential during the latter half of the period. For now have went
with a low-end VFR ceiling late tonight into Friday morning.
Visibility should also be VFR most of the period, but with enough
hints of at least "light" fog possible late tonight/early Friday
have introduced an MVFR visibility from 10-13z. Lastly, unless
convection results in briefly higher/erratic speeds, surface winds
should otherwise remain fairly light through the period at speeds
largely under 10kt and generally from a north-northeast direction.

&&

.GID Watches/Warnings/Advisories...
NE...None.
KS...None.
&&

$$

UPDATE...Pfannkuch
SHORT TERM...JCB
LONG TERM...Heinlein
AVIATION...Pfannkuch


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