Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 290747

Area Forecast Discussion
National Weather Service Hastings NE
247 AM CDT THU SEP 29 2016

.SHORT TERM...(Today and tonight)
Issued at 247 AM CDT Thu Sep 29 2016

General overview/highlights of these next 24 hours:
At least in theory/"on paper", this is probably the
quietest/"easiest" short term forecast this forecaster has
encountered in several months. However, will openly admit that
these seemingly easy/straightforward forecasts always make this
particular forecaster wonder if he might be missing something
lurking in the details. In this case, "if" (key word IF) there is
a catch/caveat, it might end up involving a bit more in the way
of at least light fog development than currently expected, but at
least for now the official forecast holds off on any formal fog
mention (more on this below). Otherwise, confidence remains very
high in literally zero chance of rain (guaranteed dry), along
with what many folks likely consider extremely pleasant/slightly
coolish early fall weather with both high/low temps averaging
slightly below normal for the date.

A look at the current scene around 2 AM/07z:
It just doesn`t get much quieter. Satellite imagery confirms
crystal clear skies over the CWA. Water vapor satellite and short
term model data reveal a highly-amplified, blocky pattern over the
CONUS, featuring a quasi-stationary and deep, nearly cut-off low
dominating the eastern states and centered over the IN/KY border
area. Meanwhile, off to our west, a broad trough is noted over the
western CONUS with a stronger, more organized low gradually
approaching the Pacific Northwest, with the main belt of northerly
jet snaking from this region then east-northeastward across
Canada. That leaves our local Central Plains region literally "in
the middle" under a fairly pronounced ridge dominating the
central states from south-to-north. At the surface, the weak cold
front that passed through yesterday has reached north TX, while
our local conditions are largely controlled by the south-southwest
reach of a roughly 1030 millibar high centered over the northern
MN/Canada border area. With our CWA almost directly within this
ridge axis, breezes are averaging from near-calm to very light

Now looking ahead in more detail through these next 24 hours...

Early this morning (through around sunrise/slightly after):
At least per the official forecast, what you see now is pretty
much what you get, with continued clear skies and near-calm to
very light northerly/easterly breezes. This is a very favorable
radiational cooling situation, and although forecasted low temps
were nudged down 1-2 degrees earlier tonight with most of the CWA
expected to bottom out somewhere 39-43, it`s sure possible that a
few spots could still drop slightly below this range, but still
"safe" from values supportive of widespread frost formation. One
possible "catch" to early this morning is the possibility of at
least light, patchy, mainly ground fog forming/persisting a few
hours either side of sunrise. However, with most models/guidance
insisting that widespread visibility reductions below 5 miles are
unlikely, have maintained a fog-free forecast for now, but will be
closely monitoring obs as sunrise approaches just in case
something a bit more noticeable might form.

Daytime hours today:
For lovers of slightly below normal early fall temps along with
lighter breezes than yesterday, it probably doesn`t get much
better than this. In the mid-upper levels, all of the main
features mentioned above remain rather persistent through the day,
with a north-south ridge axis remaining firm over the central
CONUS while the center of the low to the east meanders around over
the KY area. At the surface, the heart of the ridge axis extending
southward from the western Great Lakes edges only slightly
eastward during the day. For our CWA, this means that very
light/somewhat variable breezes this morning will gradually become
a bit more established from an easterly direction this afternoon,
but even then with sustained speeds only 5-12 MPH in most areas,
and perhaps some gusts as high as 15 MPH mainly in far western
counties (such as Dawson) by mid-late afternoon. Sky-cover wise,
kept the official forecast heavily-geared toward sunny, but there
are hints of perhaps some scattered fair weather stratocumulus
forming mainly in the eastern half of the CWA, which bears
watching in case current sky cover percentages might need
increased somewhat. Temp-wise, changed highs very little from
previous forecast, but if anything nudged up some areas 1-2
degrees based on readings the last few days slightly exceeding
expectations. As a result, have most areas aimed into very
uniform highs 68-70.

This evening/tonight:
Again guaranteed dry with the main issues consisting of: 1) how
cool will lows drop? and 2) could at least patchy fog develop
here or there, with at least one model (00z NAM) suggesting that a
bit more widespread fog could develop mainly eastern half of the
CWA? In the mid-upper levels, again very little change from the
daytime hours, although the upper trough nearing the Pacific
Northwest edges just a touch eastward, which starts to break
down/weaken the central CONUS ridge a touch, while the eastern low
just keeps on wobbling over KY and vicinity. At the surface, broad
ridging extending into our area from the northeast remains the
dominant influence, and in fact the pressure fields/orientation
remain very persistent through the night. As a result, another
night of light breezes generally at/below 5 MPH is anticipated,
mainly from an east-southeast direction. Although maybe not quite
as "ideal" of a cooling night as the ongoing one, it`s still
pretty good and as long as skies remain clear/mostly clear as
expected, this has the looks of another night that could drop a
bit colder-than-advertised. Compared to previous forecast, nudged
down lows 1-2 degrees and perhaps not quite enough, but will aim
most of the CWA 40-44 with any upper 30s most favored in typically
colder spots such as Ord. As for fog potential, pondered
introducing a generic "patchy fog" mention to much of the CWA for
the late night hours, but with SREF "probabilities for visibility
below 3 miles" still averaging rather low (despite the more
aggressive 00z NAM), held off for now and will let upcoming
day/evening shifts take another look for possible formal
inclusion. Besides, confidence in possible fog formation Thursday
night hinges somewhat on whether or not any manages to form yet
this morning in fairly similar conditions.

.LONG TERM...(Friday daytime through Wednesday)
Issued at 247 AM CDT Thu Sep 29 2016

This section will be updated within the next hour or so...please
check back.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Thursday night)
Issued at 1215 AM CDT Thu Sep 29 2016

Confidence in VFR ceiling/visibility remains fairly high through
at least the vast majority of the period, along with very high
confidence in rain/storm-free weather. Surface winds will remain
light, averaging solidly under 10kt through the vast majority of
the (if not entire) period from generally a variable to easterly
direction. That being said, there are a couple of "possible"
caveats to prevailing VFR worth mentioning:

1) Possibility of some light "ground fog" a few hours either side
of sunrise this morning? With a few models at least hinting at
this possibility, have decided to introduce a TEMPO MVFR
visibility from 10-14z.

2) Possibility of a brief MVFR ceiling during the daytime hours?
Some models hint at this occurring, but at least for now it seems
like a bit of an "outlier scenario", so have opted to keep VFR but
at least "hint" it with a FEW030 cloud mention.


.GID Watches/Warnings/Advisories...


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