Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 222327

Area Forecast Discussion
National Weather Service Hastings NE
627 PM CDT Thu Mar 22 2018

.SHORT TERM...(This evening through Friday night)
Issued at 426 PM CDT Thu Mar 22 2018

Focusing solely on these first 36 hours in this section, the
"big story" is a Marginal Risk of strong to severe thunderstorms
Friday afternoon into Friday evening. Not looking at a widespread
severe threat by any means, but the setup is looking increasingly-
favorable for a few marginally severe storms, especially within
the southern half of our coverage area (CWA). The second-biggest
story/challenge in the short term is a very tricky high
temperature forecast for Friday, as there could be almost a
30-degree gradient between our extreme northern and extreme
southern zones, with plenty of potential for 5+ degree errors in

Taking a look at the current/recent weather scene as of 330 PM...
As was expected, most folks probably agree that this in fact has
been the "nicest" day of this week, and is perhaps going to be the
overall-nicest day we see for at least another week. In the mid-
upper levels, water vapor satellite imagery and short term model
data confirm a broad, large-scale ridge encompassing the central
CONUS, flanked by large-scale troughs on either side. Locally,
other than some limited, passing high cirrus, it`s been a
sunny/mostly sunny day. At the surface, if anything, breezes have
been a touch lighter this afternoon than anticipated (kind of a
rarity!), as speeds have averaged only 5-10 MPH most areas, owing
to a weak pressure gradient. Direction is somewhat variable, but
is starting to trend more easterly with time than southerly.
Literally made zero modification to expected high temperatures
from the early-morning forecast, as we should see a range from low
60s far north to low 70s far south/southwest.

Now looking ahead forecast-wise through the next 36 hours...

This evening/tonight:
For the vast majority of the CWA, this will be a dry night with
only a gradual increase in mid-high level clouds, associated with
the very leading edges of incoming energy associated with the
approaching western trough. That being said, similar as to what
occurred last night, some limited sprinkle activity probably
cannot be ruled out between midnight and sunrise. Although could
see it occurring farther south, the only formal mention of
sprinkle chances is currently confined to our far northern zones,
which appear most favored overall. At the surface tonight, there
will be a modest uptick in wind speeds, but still only topping out
10-15 MPH for the most part, from mainly an easterly direction.
Our trend of each night staying milder than the last continues, as
lows are aimed from near-40 north, to mid-upper 40s in KS zones.
There is perhaps the slightest chance of some light fog at least
flirting with our far southwestern zones (mainly in KS) toward
sunrise, but with such meager model support decided to forego a
formal mention at this time.

Friday daytime-night:
Decided to lump the daytime and night periods into the same big
paragraph here, mainly to keep the discussion of the afternoon-
evening thunderstorm potential more cohesive. Right off the bat,
want to emphasize that despite at least small rain chances (PoPs)
existing all day in the official forecast, it`s looking more and
more probably that the vast majority of the daytime hours
(especially morning-early afternoon) will probably be largely dry,
despite the presence of considerable cloud cover, including the
likely development of a fairly low stratus deck in most areas. In
the morning, could see some spotty drizzle and/or very isolated
light showers, probably favoring our northern zones more than our
south. Then, things start turning more interesting during the mid-
afternoon through later evening time frame (mainly 4-10PM). During
this time, forcing aloft increases as a fairly progressive, low-
amplitude disturbance pushes across the heart of our area from
west-to-east. At the surface, the associated deepening surface low
(intensity around 997 millibars at 7PM) is expected to mainly
track just barely south of our CWA across central KS. However,
southeasterly winds ahead of the track of this low will draw upper
40s to perhaps low-50s dewpoints into our southern CWA. Over the
past 24 hours, models have trended up with resultant instability
potential, with both the latest NAM/GFS suggesting that mixed-
layer CAPE could flirt with 1000 J/kg near and south of the state
line, with mainly less than 500 J/kg farther north and minimal
CAPE north of I-80. Deep layer shear will be fairly strong as
well, on the order of 50-60+kt. Although it is still too soon to
break down the finer mesoscale details, a blend of various
deterministic and higher res model solutions clearly suggests that
at least isolated strong to severe storm activity could break out
in mainly our southern half during the late afternoon/evening,
capable of producing at least quarter size hail/60 MPH winds,
while weaker rain shower/thunderstorm activity prevails within
the northern half of the CWA, but perhaps with small hail.
Although NOT a likely scenario, it`s worth mentioning that there
could even be a VERY conditional chance for a brief tornado in our
southern zones, IF an isolated supercell storm should happen to
form. Overall though, it would mainly be a hail/wind event. Don`t
want to dwell on this much, but also want to make it clear that
this forecaster feels the official SPC Day 2 outlook may be
focused a bit too far north into Nebraska, and unless models
suddenly change, am fully anticipating the SPC Day 1 outlooks
tonight/tomorrow to shift the main focus more so near/south of the
KS-NE border. At any rate, will end this particular topic for
now, and allow upcoming night shift forecaster to better assess
the details of any severe threat. Precip-wise, most activity
should be over with by midnight, except for perhaps some lingering
light showers in our east. Briefly touching on other elements of
Friday/Friday night...temperature- wise highs are very tricky.
Most of our CWA is expected to be blanketed in clouds, but our far
south could see more sun. Officially, am calling for a big
gradient from low-mid 50s far north to near-80 extreme south, with
the Tri Cities near-60 in the middle. Daytime winds will be
breezy from the east-southeast (gusts 25-30 MPH), with night-time
winds then becoming breezy from the north-northwest behind the
departing low. Low temps Friday night are aimed upper 30s north to
mid 40s south, so not overly cold.

.LONG TERM...(Saturday daytime through Thursday)
Issued at 426 PM CDT Thu Mar 22 2018

With so much focus on the first 36 hours above, once again this
section gets the "shorter end of the stick" detail-wise. Focusing
on the broad/big-picture however, here are the most important

1) The forecast is "littered" with a multitude of precipitation
chances during the entire Sunday-Thursday time frame. However, am
rather skeptical of our small chances for Wednesday-Thursday (as
populated by our default multi-model blend), and would not be
surprised to see these removed in later forecasts. As a result,
the MOST FAVORED time frame for precip still appears to focus
Sunday-Tuesday, as the very slow-moving "parent" western trough
gradually lumbers out of the western CONUS into the central
states. Confidence in the day-to-day details is low, as even as
early as Sunday daytime, models disagree whether this will be
mainly a dry period, or perhaps one with scattered showers and/or
drizzle. Some of the overall-best rain chances will likely focus
Sunday night-Monday night, during which time the primary surface
low pressure system and associated frontal boundaries will cross
the region.

2) The Sunday night-Monday night period also happens to be the
only time frame with a formal thunderstorm mention, currently
mainly favoring southern/eastern zones but may need expanded to
include more of the area as it gets closer. It`s still a bit far
out to speculate severe potential, but depending on frontal timing
Monday could be another "Marginal Risk" type of setup, and this
bears watching.

3) For those concerned with weekend weather, Saturday still looks
dry, albeit somewhat breezy. As stated above, Sunday may or may
not be mainly dry as well, with plenty of model disparity.

4) Although parts of the CWA carry a formal snow mention for the
late-night/early morning hours on some days due to low
temperatures dropping into the low-mid 30s, snow DOES NOT look
like a big factor next week, barring some pretty big model

5) Temperature-wise, there were no big changes made versus the
previous forecast. Overall, readings look to average relatively
close to late-March normals, in other words, not too warm, but
also not truly cold by any means either. More specifically, highs
on most days in most places are aimed between the upper 40s-upper
50s, with overnight lows mainly in the 30s on most nights, with
some 40s. Depending on how much sunshine is around, Monday has the
potential to be one of the warmer days, especially in our south,
with 70s possible mainly in our KS zones.


.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 624 PM CDT Thu Mar 22 2018

Quiet weather with VFR conditions expected this evening/overnight,
but as we get toward daybreak tomorrow, low level stratus becomes
more of a concern. Models showing MVFR then IFR ceilings moving in
for the second half of this TAF period at both terminal sites. Not
expecting notable changes in wind direction through the period,
remaining east-southeasterly, but gusty conditions will be
possible during the daytime hours tomorrow.




SHORT TERM...Pfannkuch
LONG TERM...Pfannkuch
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