Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 171012

Area Forecast Discussion
National Weather Service Hastings NE
512 AM CDT Mon Oct 17 2016

.SHORT TERM...(Today and tonight)
Issued at 512 AM CDT Mon Oct 17 2016

For having little no chance of precipitation, these next 24 hours
have presented a challenging little forecast with regard to
various elements including: dense fog concerns (for this morning),
critical fire weather conditions (for this afternoon) and the
likelihood of at least near-record high temperatures in the mid-
80s to around 90. Both a Dense Fog Advisory and Red Flag Warning
have been issued (our first RFW since early April in fact). For
any further discussion about the fire weather/danger situation
please refer to the separate "Fire Weather" section below.

Unfortunately not much time to dive into details this morning
thanks in part to time spent coordinating/refining the
aforementioned advisory/warning products...

Taking a quick look at the current scene as of 0930z/430AM,
overall no big surprises overnight as the CWA currently resides
under a combo of mostly clear to partly cloudy skies (mainly high
level cirrus), although the jury is still very much "out" on
whether or not dense fog development will ultimately be more
widespread or more patchy/hit and miss in nature. So far our
limited network of airport obs/webcams suggest the latter, but
with sunrise not occurring until nearly 8 AM these days there is
still plenty of time for things to take a downhill turn over the
next several hours especially along/near a weak front draped from
northeast to to southwest across our CWA, and as insisted upon now
with the past several runs of the HRRR/RAP13 models. It`s actually
a bit of a complex surface situation across this front within the
CWA, which extends northeast from a roughly 996 millibar low
currently over north central KS. To the north of this boundary,
light, generally northerly winds are promoting cooler temps/lower
dewpoints while milder temps/higher dewpoints (up to around 60)
are found in the southeast CWA in the presence of light southeast
to light/variable breezes. In the mid-upper levels, fast west-
southwest flow is centered just north of the CWA, featuring a
progressive shortwave trough and upper level jet streak. Low temps
this morning are expected to bottom out mainly 40s northwest to
55-60 southeast.

Now looking ahead forecast-wise through these next 24 hours or

Early this morning through sunset:
Still expecting dry conditions today, as the aforementioned mid-
upper forcing is expected to stay far enough north of the area to
keep mid-level saturation from occurring locally. Because of that,
the focus is on morning fog/afternoon fire weather and trying to
pin down just how hot it might get. At the surface, the low
pressure center over northern KS will quickly scoot northeast
toward WI over the course of the day, allowing a cold front to
surge eastward across the CWA (a front more in the sense of
increasing west winds than falling temps, as the main temp drop
moves in after peak heating). This will be a classic, westerly
winds/downslope flow regime, which often results in an efficient,
sometimes warmer-than-expected temp regime and drier-than-expected
dewpoint regime (hence the fire weather concerns). Before this
steady westerly breeze takes hold though, very light winds and low
temps/dewpoint depressions along the aforementioned surface
trough will likely promote increasing coverage of locally dense
fog as the morning wears on. Although the existing advisory may
ultimately be plenty generous in size, it should at least capture
the heart of the area with dense fog potential. This fog could be
rather slow to burn off especially in far eastern zones, and am
not necessarily convinced that the 16z/11AM expiration time will
suffice but will run with it for now. Meanwhile, western counties
in the advisory may be able to be cancelled early. Temp-wise,
obviously any stubborn morning stratus/fog in central/eastern
zones could delay a big rise, but with westerly breezes and mostly
sunny skies expected this afternoon a big jump is likely.
Confidence is forecasted highs is only "moderate" at best, but
opted to increase previous forecast generally 1-4 degrees, aiming
for 83-87 most Neb zones and 85-92 in KS.

This evening/tonight:
Once the late afternoon/early evening fire weather concerns abate,
should be a quiet/mostly clear night with no fog concerns for a
change thanks to drier air and northwesterly breezes in the wake
of the mid-level wave departing off to our northeast. Basically
speaking, northwest winds could still be a bit gusty in the
evening, but settle into the 5-10 MPH range late in the night.
These decreasing-but-still noticeable light winds will certainly
preclude an ideal radiational cooling situation, but with low-
level cold air advection in play, opted to nudge down forecasted
low temps up to a few degrees, aiming most of the CWA into the
43-48 range.

.LONG TERM...(Tuesday through Sunday)
Issued at 423 AM CDT Mon Oct 17 2016

A slight southwesterly component to the flow aloft will dominate
through Wednesday in advance of the next upper trough. Surface
high pressure will move overhead Tuesday with light winds and
highs near 70. The next upper trough will move through Wednesday.
A secondary surge of cooler air will arrive as this disturbance
moves through. Temperatures will be closer to climatic norms, with
highs in the low 60s Wednesday and Thursday. As this disturbance
moves through there is enough lift to develop a few showers. The
best chances look to be north of I-80 during the day Wednesday.

Friday - Sunday:
A couple different surface troughs followed by surface high
pressure will move through causing a wind shift, but little else.
With a lack of moisture and upper level ridging dominating, the
forecast is dry. Highs will be in the low 70s with overnight lows
in the upper 30s and 40s.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Monday night)
Issued at 104 AM CDT Mon Oct 17 2016

General overview:
While confidence is high that VFR ceiling/visibility will prevail
through at least the latter half of the period at KGRI and quite
possibly the entire time at KEAR, there is considerable
uncertainty especially with regard to these first 9-10 hours, as
especially KGRI could rapidly "tank" to VLIFR conditions in dense
fog, potentially for several hours. Confidence is high in dry
/rain-free conditions at both sites. See below for more element-
specific details...

As already mentioned, these first 9-10 hours will be rather
challenging, as there is a good chance that especially KGRI will
see initially MVFR visibility deteriorate to at least IFR and
possibly VLIFR in dense fog. Meanwhile, KEAR is JUST far enough
west that "in theory" it should narrowly avoid fog issues, but
this is no guarantee either. The bottom line is, that while
confidence was not high enough to go prevailing VLIFR at KGRI, it
was introduced as a TEMPO from 08z-12z and could very well extend
a bit later, while KEAR has been left as VFR but will "hint" at
light fog potential with a "6SM BR" mention. Once boundary layer
winds turn more westerly by mid-late morning, confidence is high
in VFR from then on.

Surface winds/possible low level wind shear (LLWS):
The majority of these first 12 hours will feature a
light/variable surface wind, thanks to the presence of a weak
trough axis working across the area. Then, by late morning/early
afternoon, a pronounced increase in westerly breezes will take
place behind a passing front, with sustained speeds increasing to
at least 15-20kt and gust potential 20-25kt. These westerly
breezes will then let up somewhat during the evening. As for LLWS,
some models suggest there could be a period of "TAF-worthy"
LLWS centered around 03z tonight but given this is so far out
toward the end of the period and with plenty to deal with before
then, will hold off on including this for now.


Issued at 500 AM CDT Mon Oct 17 2016

For the first time in our CWA since early April, the combination
of dry/drying vegetation (thanks largely to recent frost/freezes),
low relative humidity and gusty wind winds has met thresholds
worthy of Red Flag Warning issuance, and we have coordinated with
neighboring offices to the west and south to issue an RFW for this
afternoon for counties mainly west of a Greeley-Hastings-
Plainville KS line.

That being said, this is not necessarily a "slam dunk" to
technically reach our locally-defined Red Flag criteria, and in
fact may be fairly marginal, especially in counties south of
Highway 6 where sustained winds/gusts may struggle to get as
strong as especially those counties north of I-80. However, have
opted to include these more marginal counties as well due to
mainly coordination with neighboring offices and also the
possibility that westerly gusts could somewhat exceed expectations
(as often happens in downslope wind regimes). There is a bit more
confidence in relative humidity (RH) dropping at/below 20 percent
within the advisory area, but this also is somewhat dependent on
the combo of forecasted near-record high temperatures
materializing along with steadily falling dewpoints. All things
considered, the overall "worst" combo of gusty winds/RH are
expected to focus within the northwest quadrant of the CWA (mainly
counties along/north of I-80 and along/west of Hwy 281).

Closing with a quick review of our local fire weather thresholds:
"Critical" fire weather in our CWA is defined as the 3+ hour
overlap of relative humidity (RH) of 20-percent-or-lower and
sustained winds/gusts of 20+ MPH/25+ MPH. "Near-critical" is
defined as the overlap of 25 percent-or-lower RH and sustained
winds/gusts of 15+ MPH/20+ MPH (in the presence of sufficiently
dry vegetation).


Issued at 500 AM CDT Mon Oct 17 2016

Our two primary long term climate records sites (Grand Island and
Hastings airports) could potentially threaten record highs for
Oct. 17th, although the current official forecast technically falls
slightly short. These current records are as follows:

Grand Island...90 in 1910
Hastings...87 in 1961


NE...Dense Fog Advisory until 11 AM CDT this morning for NEZ039>041-

     Red Flag Warning from noon today to 7 PM CDT this evening for

KS...Dense Fog Advisory until 11 AM CDT this morning for KSZ006-007.

     Red Flag Warning from noon today to 7 PM CDT this evening for



SHORT TERM...Pfannkuch
LONG TERM...Billings Wright
FIRE WEATHER...Pfannkuch
CLIMATE...Pfannkuch is the U.S. government's official web portal to all federal, state and local government web resources and services.