Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 101824
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
1224 PM CST Sun Dec 10 2017

.UPDATE...
Issued at 1158 AM CST Sun Dec 10 2017

Have been working on updating all products to reflect the Red Flag
Warning issued earlier this morning. Most of our area will
continue to see observations right around our critical fire danger
thresholds through this afternoon.

&&

.SHORT TERM...(Today and tonight)
Issued at 437 AM CST Sun Dec 10 2017

We`re finally here: the much-advertised warmest day of the month
so far (at least for the majority of our local area) and also the
warmest day of the current 7-day forecast. About the only drawback
will be breezy (albeit not overly-windy) conditions, with at
least a few hours of gusts into the 20-25+ MPH range. Unfortunately,
the combo of these breezes and very low relative humidity will
push us rather close to meeting "critical" fire weather conditions
this afternoon in much of the area. For any further discussion of
today`s fire weather situation, please refer to the separate FIRE
WEATHER section below.

Taking a look at the current/recent weather scene as of 10z/4AM:
The night is playing out very much as expected 24 hours ago.
Satellite reveals essentially clear skies. In the mid-upper
levels, water vapor imagery and short term model data clearly
reveal the Central Plains residing under pronounced north-
northwest flow, directed between an expansive/large scale ridge
and trough dominating the western and eastern CONUS, respectively.
At the surface, a trough axis/effective warm front continues
pushing east across the region. In the wake of this feature, west-
northwest breezes have picked up overnight versus what they were
near sunset, currently averaging at least 8-15 MPH. The
combination of these breezes and warm air advection has resulted
in overnight temperature rises of 5-10 degrees in many spots, with
most places currently reporting seasonably-mild readings in the
33-40 range. While small downward trending is still possible
through sunrise, most places will probably not drop below 30 again
before daytime warming kicks in.

Now looking ahead forecast-wise through today-tonight...

Today:
As long as you don`t mind a little breeze, get out there and enjoy
this. In the mid-upper levels, uneventful north-northwest flow
continues. While there will probably be limited high level cirrus
drifting in from the north, skies should average sunny to mostly
sunny at worst. At the surface, northwest breezes will largely
peak in intensity 11AM-3PM with sustained speeds generally 15-20
MPH/gusting around 25 MPH, but with a gradual decreasing trend as
the afternoon goes on, and easing to only around 10 MPH by sunset.
The biggest question mark is probably how warm does it get? After
seeing yesterday`s high temp forecast work out rather well, opted
to take a similar approach for today, which resulted in nudging
most places up 1-2 degrees from the previous. The result is a
range from mid-upper 50s far northeast, low 60s central (including
Tri Cities) and mid 60s southwest. Although within "shouting
distance" for sure, our current official forecast falls 3 degrees
short of the Dec. 10th record high at Hastings (64) and 5 degrees
short of the Grand Island record (66). For most of our CWA,
today`s highs will be 20-25 degrees above normal.

This evening/tonight:
While most of the night will be pretty uneventful, we will start
to see the changes taking place that will usher in the upcoming
cool-down as described in the Long Term section below. In the mid-
upper levels, a potent clipper disturbance will start the evening
over southern Saskatchewan, but by night`s end will rapidly dive
southeast to the NE/SD/IA/MN border area. While our local domain
will certainly remain dry through the night, the main effects of
this approaching system will be at least a limited increase in
passing mid-high level clouds, and more so a noticeable increase
in winds post-midnight. Pre-midnight winds will only average 5-10
generally westerly. But then between midnight and sunrise, they
will turn more northwesterly and increase to 10-20 MPH, with some
late-night/early morning gusts of 25+ MPH likely especially north
of I-80 in Nebraska. Temperature-wise, hourly trends will likely
be tricky to pinpoint given that readings will probably fall
fairly quickly in the lighter evening wind regime, but then steady
out or even rise as breezes/mixing pick up later in the night. At
any rate, actual lows are officially aimed into the 30-33 range
most areas, but would not be surprised to see several spots
struggle to drop below 35.

.LONG TERM...(Monday daytime through Saturday)
Issued at 437 AM CST Sun Dec 10 2017

Models remain in good agreement at the start of the long term period
Monday morning, showing continued northwesterly flow aloft, set up
between broad troughing over the eastern CONUS and ridging extending
north across the west coast/western Canada. An embedded shortwave
disturbance looks to be making its way through MN around 12Z Monday,
pushing further into the Great Lakes/Midwest through the day. While
no precipitation is forecast for Monday with this disturbance, it
will be pushing a surface cold front through the region. This front
will bring a reinforcing shot of northwesterly winds, which will be
on the increase in the morning. Forecast soundings show increased
mixing potential into stronger winds aloft, and sustained speeds are
expected to increase into roughly the 25-30 MPH range, with gusts
near 45 MPH. With cooler air advecting in from the north, highs will
be lower than today, but still above normal, topping out in the mid
40s to lower/mid 50s. Fire weather concerns remain for southwestern
portions of the area, mainly along/south of a Beaver City to Beloit
line. Forecast dewpoints are on the low side of guidance, and
resulting RH values for that southwestern third of the CWA drop into
the 20-25% range, with the lowest values in Rooks County. Will
continue to mention in the HWO, right now dont have critical
conditions hitting the 3 hr time criteria, but this will have to be
closely watched by the upcoming shifts.

Through the rest of the work week, the dry forecast remains in
place. Northwesterly flow continues in the upper levels, though
around Friday, the pattern looks to deamplify as a system moves into
the Pac NW. No big changes in temperatures are expected, with highs
varying from the mid 40s to mid 50s. Winds are expected to remain
west to northwesterly, with Wed/Thurs looking to be on the breezy
side. Getting into Saturday, model blend threw in some 20 PoPs
across the northern half of the CWA, associated with a quick moving
disturbance that a few models hint at. Confidence is pretty low at
this point, will see if future runs hold onto the feature. No
notable change in temps for Sat.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Monday)
Issued at 1158 AM CST Sun Dec 10 2017

Breezy northwest winds are expected to continue through mid to
late afternoon and then gradually die off this evening before
picking back up again by mid to late Monday morning. Clear to
mostly clear skies are expected through most of the TAF valid
period with maybe some increasing lower clouds Monday morning, but
will continue the VFR ceilings throughout the forecast period for
now. If we do catch some low clouds later Monday morning they
would likely be in the 2000 to 5000 ft agl range.

The other concern will be strong low level wind shear after
midnight tonight and through at least mid morning on Monday.

&&

.FIRE WEATHER...
Issued at 437 AM CST Sun Dec 10 2017

Regarding "very near-critical" fire weather conditions across
nearly all of our CWA this afternoon:

The combination of breezy winds and low relative humidity (RH)
values forecasted for this afternoon push us about as close as
possible to meeting "critical" fire weather conditions, but
technically fall just a bit short. As a result, have refrained
from issuing a formal Warning but have emphasized fire weather in
products such as the Hazardous Weather Outlook (HWOGID) and also
a Special Weather Statement (SPSGID).

Getting into more specifics, the combination of northwest winds
gusting at least 20-25 MPH and RH falling as low as 13-25 percent
will easily promote at least near-critical conditions, especially
between noon-4 PM. Localized critical conditions will probably be
realized too, but these appear unlikely to last more than one to
two hours at any given location, largely due to the expectation
that wind speeds should gradually diminish as the afternoon wears
on. The bottom line: day shift will have to closely watch the
interplay between winds/RH and make sure things don`t trend
"worse" than currently indicated, or a short lead-time Warning may
prove necessary.

Closing with a quick review of our local fire weather criteria:
"Critical" means the 3+ hour overlap of relative humidity (RH) of
20- percent-or-lower and sustained winds/gusts of 20+MPH/25+MPH.
"Near-critical" means the overlap of 25-percent-or-lower RH and
sustained winds/gusts of 15+MPH/20+MPH.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Red Flag Warning until 5 PM CST this afternoon for NEZ039>041-
     046>049-060>064-072>077-082>087.

KS...Red Flag Warning until 5 PM CST this afternoon for KSZ005>007-
     017>019.

&&

$$

UPDATE...Wesely
SHORT TERM...Pfannkuch
LONG TERM...ADP
AVIATION...Wesely
FIRE WEATHER...Pfannkuch



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