Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 241723
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1223 PM CDT Mon Apr 24 2017

.SHORT TERM...(Today and tonight)
Issued at 411 AM CDT Mon Apr 24 2017

Plenty of cirrus and breezy winds this morning are helping to
maintain very mild temperatures across the region. With a few
light showers popping up to our west the last couple of
hours...opted to keep a slight chance for a light shower or
sprinkle north of I-80 through around noon...as additional light
showers potentially develop and track northeast. Otherwise...
expect a variably cloudy day with very mild afternoon temperatures
across the local area as a surface trough tracks across the area
from the west and 850 MB temps warm a couple of degrees above
yesterday values.

With the surface trough approaching...expect winds to slowly
diminish across the region through the early afternoon
hours...with the strong southerly winds expected to
correspondingly shift off to the east by afternoon. So while it
will be a breezy start to the day, a somewhat more pleasant
afternoon is expected as temperatures soar to near 80 in spots and
winds decrease from west to east. Thanks to some moisture
advection across the region and more shallow mixing anticipated
this afternoon...fire weather concerns appear diminished from 24
hours ago...and opted to no longer mention near critical fire
weather conditions in the HWO.

As we then transition into the evening and overnight
hours...expect the surface cold front to encroach on our local
area with some modest elevated instability preceding its passage.
As a result...went ahead and introduced the possibility of some
non-severe isolated thunderstorms during the pre-dawn hours. With
this cold front not expected to cross the local area until later
in the day Tuesday...expect another mild night...with overnight
low temperatures running 5-10 degrees above normal for late April.

.LONG TERM...(Tuesday daytime through Sunday)
Issued at 500 AM CDT Mon Apr 24 2017

General overview of this 6-day period:
For those who have been following along over the weekend, again no
truly major changes to the overall expectations of this very
active time frame. Summing it up in just one sentence: Get ready
for a noticably-cooler (especially during the day), mostly cloudy,
rather breezy/windy and at-times wet stretch of several days. By
the time this weekend is over, many folks will likely be longing
for another stretch of mild and relatively sunny weather such as
the one we are just wrapping up. Will now run down 4 key
highlights/takeaways from this latest forecast package:

1) Good news/bad news depending on one`s perspective (along with a
temperature summary):
It truly is a good news/bad news proposition. On the positive
side (for most), we are still looking at several opportunities for
rain, with the highest chances (PoPs) and overall-highest totals
focused during the Thursday night-Saturday night time frame. As
has been consistent for days now, official cumulative 7-day
precipitation totals from Weather Prediction Center (WPC) continue
calling for a widespread coverage of around 2" of rain for pretty
much our entire county warning area (CWA), but as we all know,
odds are high that some spots will ultimately end up with less
than this and others perhaps a bit more. On the negative side (for
most), we are looking at the coolest multi-day stretch we`ve had
in a month, along with plentiful clouds. Although far from earth-
shattering for late April most of the CWA will struggle to only
realize highs in the 50s for several days in a row, and although
not currently reflected in the official forecast, do not be
surprised if more of the area gets stuck in the 40s on a few
days. As for overnight lows, again not looking at anything record-
breaking, but most nights will feature readings bottoming out
between the mid-30s and low-40s. While conditions on most nights
should be too windy and/or too cloudy to support frost formation,
there is at least one night (Wednesday night/Thursday morning)
that is a bit more concerning, with lows forecasted into the low-
mid 30s CWA-wide, along with current indications for fairly light
winds and no worse than partly cloudy skies. Some far northern
/west-central areas could drop slightly below freezing. Given this
is still 3 nights out, not a "slam dunk" by any means, but did
introduce a generic "patchy frost" mention to the official
forecast along with a mention in the Hazardous Weather Outlook
(HWOGID).

2) Model trends/timing:
Not surprisingly, primary 00z models (NAM/GFS/ECMWF) continue
coming into increasingly-better agreement/consensus on at least
the larger-scale synoptic features through the first part of the
longer-term periods. By this weekend, some pretty substantial
differences in the timing/movement of the primary closed upper
low/vort max begin to emerge (in short, the latest ECMWF lifts it
more north-northeast across the Upper Midwest while the latest GFS
tracks it more across KS/OK and IA/MO), but somewhat surprisingly,
the net resulting weather at the surface is in fairly decent
agreement, at least for now. Of course, as anybody reading this
knows, there is still a boatload of uncertainty in the forecast
details especially beyond Day 4, so be sure to stay up to the
latest as potentially substantial changes to precip trends/temps
are still on the table, despite the relative consistency of late.

3) Thunderstorm/severe weather potential (or lack thereof):
As discussed here especially last night, it has been a challenge
lately trying to determine what particular periods might warrant a
formal mention of thunderstorms (as opposed to just generic
rain/showers), and because of the whims of model run-to-run
variations in instability and also multi-office collaboration,
various formal mentions of storms have come and gone over the
past few days. In coordination with the short-termer handling
tonight`s forecast, we have re-introduced a slight chance for
non-severe thunderstorms within Nebraska portions of the CWA for
right away Tuesday morning. Beyond this though, although we cannot
rule out later forecasts eventually warranting a mention of
thunder as some periods get closer (perhaps Thursday night being
one?), for now we opted to just omit a thunder mention for the
entire long-term beyond Tuesday. If anything, the latest ECMWF and
especially GFS runs have come into better agreement than 24 hours
ago that our local area appears to be just too far north and/or
northwest to realize appreciable instability. Following suit with
this trend, the latest SPC Day 5 severe storm outlook for Friday
no longer comes even close to even clipping our southern CWA with
the 15% area, and the Day 6 for Saturday is even farther south and
east. In other words, barring some pretty major changes in the
coming days, any "big time" severe threat Friday and/or Saturday
should mainly be a KS/OK border area southward issue.

4) Could some late-season snow (yes SNOW) possibly pose an issue
especially in our far west-northwest counties this weekend?:
Well, although it is FAR too early to try pinning down specifics,
taking raw model output literally at this point, the airmass
associated with the main upper low this weekend currently appears
chilly enough to support at least light measurable snow especially
slightly to the west/northwest of our CWA over western/north
central Neb, with our western fringes being "on the edge" of
possibly realizing some snow or at least a rain/snow mix. It will
be days before we truly can determine whether snow will
potentially be more of a player for our CWA, but this forecast
package did at least introduce the "s-word" possibility to the
Dawson County area in our far-west for Saturday night. Earlier in
the week, some models try spitting out a touch of light snow
mainly late Tuesday night/early Wednesday in our far northwest as
well, but barring substantial changes, in all reality any
measurable precipitation should be vacated from this area before
it becomes cold enough to support snow, so have stubbornly
continued leaving precip type for this time frame as plain rain.

With the most important/key points covered, will wrap this up with
some fairly brief day-to-day expectations:

Tuesday daytime-night:
Over the course of the day and into the night, the first primary
mid level trough of the week will be in the process of traversing
the Central Plains. The primary surface low associated with this
system will track to our south along the KS/OK border and points
east-southeast from there, so we will solidly be in the cool
sector of this system. In fact, the cold front passing through
during the day will be a rude dose of reality after today`s
warmth, with northerly gusts up to around 30 MPH making the highs
ranging from upper 40s north to low 60s south feel even chillier.
Rain-wise, especially the daytime features a halfway decent chance
of showers/a few non-severe thunderstorms, especially in our
north. Some chilly rain could linger into the night, but most
models suggest very little precip potential post-sunset so these
PoPs may be too high. Lows will likely fall well into the mid-
upper 30s most areas but winds will be too strong for frost
issues.

Wednesday daytime-night:
Despite some highly-uncertain lingering small PoPs during the day,
in all reality this should be a pretty dry 24 hours as we reside
in between systems. This is also our best chance of catching some
sun during the week, although it will remain cool and breezy from
the north during the day. See above for more on possible
frost/freeze concerns for Wednesday night.

Thursday-Friday night:
Over this time frame, the second/larger low pressure system of the
week will start taking shape over the western CONUS, with smaller
scale lead waves kicking out into our area and promoting
increasing chances for off-and-on rainfall, especially from
Thursday night onward.

Saturday-Sunday:
At least at this point, this looks like a rather "crummy" weekend
(outside of beneficial precip of course). Both days feature
similar highs only in the low-mid 50s, and there are hints this
could be too optimistic. Although they vary in the details, both
the ECMWF/GFS show fairly high/widespread precip chances
especially through Saturday night, and as earlier mentioned, we
may even have to watch for a little snow flirting with our west.
It will also likely be rather breezy/windy from some sort of
northerly direction as the main surface low again passes by to our
south.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Tuesday afternoon)
Issued at 1216 PM CDT Mon Apr 24 2017

Scattered midlevel clouds have developed and will continue into
the early afternoon. There may be a sprinkle or two, but didn`t
include at the TAF sits due to the limited coverage and low
impact.

Winds are currently starting to shift southwesterly and
decreasing. Expect this trend to continue into the evening and
overnight as winds eventually shift to the north and northeast by
tomorrow morning. Chances for precipitation and likely MVFR sky
conditions return to the forecast for tomorrow morning into the
afternoon.

 &&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&

$$

SHORT TERM...Rossi
LONG TERM...Pfannkuch
AVIATION...Mangels



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