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Forecast Discussion
NWS Omaha/Valley, NE


000
FXUS63 KOAX 162350
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
550 PM CST Sun Feb 16 2020

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 312 PM CST Sun Feb 16 2020

Forecast Summary:

Colder temperatures and a couple of chances for light
precipitation are forecast through mid week. Then we should see
warming once again for next weekend.

This afternoon through Monday:

Clouds thinned out this morning allowing for plenty of sunshine this
afternoon. And along with southwesterly winds, temperatures had
risen into the 50s in all but far northern parts of Nebraska and
west central Iowa.

The mild temperatures of this afternoon will be heading downward as
we approach mid week as a couple of low pressure systems drop
through the region. The first will track across the Northern Rockies
tonight then through eastern Nebraska and western Iowa Monday
afternoon. Warm advection ahead of this system will lead to
increasing cloud cover overnight, with modest isentropic upglide
helping saturation of mid then low levels as the night goes on.
Weak forcing suggests at least some precipitation should fall
across mainly the northern half of our CWA from after midnight
through about noon before we are in subsidence region of exiting
wave. Mild temperatures tonight combined with increasing clouds
and cooler air lagging behind system suggest most precipitation
will fall as rain across our CWA. Forecast soundings do indicate
snow in our north, but with warm grounds, not expecting much
accumulation.

Winds turn northwesterly later Monday morning with modest cooling to
follow. However with temperatures remaining near or above freezing
overnight, we should see a rebound into the 40s for most of our area
before cooler air invades for the afternoon.

Tuesday through Wednesday:

With temperatures beginning a downward trend behind Monday`s system,
a strong shortwave is scheduled to rotate through the region Tuesday
and Wednesday. Airmass behind attendant cold front should drop
temperatures well below mid-February normals, especially on
Wednesday when 1047mb surface high pressure will settle into Iowa.
850 temperatures drop into the -10 to -15C range across our CWA,
indicating highs in the 20s are all we can hope for Wednesday.

Ahead of mid level shortwave trough, forcing under right entrance
region of 110kt upper level jet inducing upglide over cool surface
air will drive light snow formation across our northern CWA
beginning Tuesday night and continuing through Wednesday while
slowly sinking south. Forecast soundings cool sufficiently to deepen
dendritic growth zone on Wednesday indicating a relatively efficient
snow-producing environment. However mixing ratios are low, generally
1 g/kg or less, and forcing is weak, so not expecting snow to pile
up very quickly. A consensus of model output concurs with this
evaluation, point to an inch or two favoring the northern half of
our forecast area.

Thursday through Sunday:

A warming trend continues to be advertised for late this week into
the weekend. Mid level heights begin to rise Thursday as mid level
shortwave trough swings east. Southwest surface flow sets up
Thursday afternoon, but cool surface temps will be slow to scour
out. Still, highs back into the 30s should be realized Thursday.
Warming continues into the weekend as 850 temps swing back into the
5-8C range by Saturday, suggesting highs in the 50s once again. By
Sunday, models diverge on mid level low tracking through the region.
GFS rotates low northeast through Kansas, spreading a swath of rain
across much of our area. The ECMWF tracks the low through the
Southern Plains, keeping precipitation south of our area. Have
split the differences in this regard and kept a small chance for
perception for Sunday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 541 PM CST Sun Feb 16 2020

Later tonight, a system will move through the area, bringing
along the chance for light rain and snow showers near KOFK. There
will be a chance for showers at KOMA and KLNK in the early
morning hours on Monday. A sharp wind shift is expected
throughout the area early tomorrow morning, with winds switching
from southerly to northwesterly. Winds will be relatively strong,
15-20 kts with gusts over 25 kts possible. Lower ceilings are
expected late tonight and through the morning, bringing along
possible MVFR conditions, although these conditions should clear
out by midday.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

DISCUSSION...Dergan
AVIATION...Gunkel

NWS OAX Office Area Forecast Discussion



Forecast Discussion
NWS Hastings, NE


000
FXUS63 KGID 170110
AFDGID

AREA FORECAST DISCUSSION
National Weather Service Hastings NE
710 PM CST Sun Feb 16 2020

...Aviation and Short Term Update...

.UPDATE...
Issued at 710 PM CST Sun Feb 16 2020

A few notes/updates regarding the overnight/early AM forecast:

Although we are still expecting very low-impact weather
overnight, a few minor modifications have already been made since
the "original" updated overnight forecast came out a few hours
ago:

1) Small chances for light rain and/or just sprinkles have been
expanded southward to include more of the CWA, including portions
of our KS zones. These types of moisture-starved systems are
notorious for generating light precip over a larger area than some
models suggest, even if it is just sprinkles. Often the
coarser/broadbrushed nature of QPF from models such as the ECMWF
captures this reality better, so at least have small chances for
sprinkles and/or light rain mentioned everywhere the ECMWF
depicts the possibility. Again though, we are talking LIGHT
precipitation, with most of the area unlikely to measure more than
0.01-0.02" at most.

2) Removed any mention of light snow/or flurries that might have
previously existed. Temps aloft just appear too remain too warm
to support anything other than liquid droplets. To be fair, technically
our forecast does show overnight low temperatures falling as low
as 31-32 degrees in some areas, which means that "technically" a
brief period of light freezing rain/freezing sprinkles cannot be
ruled out. However, given that the vast majority of any overnight
precip should end before temps drop this low, and also the fact
that ground temps are fairly warm after the mild weather the past
few days, feel that any very small chance of freezing
precipitation is NOT worth mentioning in official forecast
products.

3) Cut back on the mention of "patchy fog" that was introduced to
eastern portions of the CWA for late tonight into Mon AM. The
last few HRRR/RAP modeled-visibility runs are quite insistent
that the vast majority of fog in the wider region tonight should
favor southern/eastern parts of KS, mainly 50+ miles outside our
CWA. In addition, the widespread mid-high cloud cover should (in
theory) work against fog formation as well. So, as a compromise
between previous forecast and latest HRRR/RAP trends, pulled the
majority of patchy fog mention from much of the eastern CWA, but
left a limited mention of it in our southeastern 1/4, mainly
southeast of a Geneva-Smith Center line. Even if some fog does end
up developing in our southeast, would expect it be mainly of the
"light" variety (visibility near-to-above 3 miles).

&&

.SHORT TERM...(This evening through Monday night)
Issued at 318 PM CST Sun Feb 16 2020

Upper air and satellite showing continued northwesterly flow in
place across the region today, driven primarily by broad troughing
over the eastern CONUS. It`s been a nice pleasant end to the
weekend, the only thing that didn`t work out quite as expected
24hrs ago was how long it has taken for the thicker upper level
cirrus to work into the area. Was thinking yesterday that the CWA
would see partly-mostly cloudy skies already this morning, but it
ended up taking a few hours longer...but doubt too many folks are
complaining about having a little more sun. Overall, forecast
highs have been on track, with mid-afternoon temps in the lower-
mid 50s...but a few locations may end up a couple degrees warmer
than expected. Winds through the day have been SSWrly, and while
there were a few locations with occasional gusts near 20 MPH
(mainly in the S and E), speeds for the most part this afternoon
have been around 10 MPH.

Focus for the short term period turns to this evening through
early Monday morning, as precip chances return to the forecast.
Even with this just hours away, confidence in exactly how things
will pan out is not high. Models showing a weak shortwave
disturbance (the first in what will be a series of waves to affect
the area over the next couple days) moving east across the
Dakotas/northern Nebraska tonight, and while chances for
measurable precip are not high, they can`t be completely ruled out
either. Forecast soundings/time heights continue to show overall
lower level moisture is lacking, but kept the slight change PoPs
going HWY 6-north, and have a mention of sprinkles/flurries
approaching the NE/KS state line. Temperatures overnight should
keep the main measurable precip type as liquid. A few models also
showing the potential for the development of fog late tonight-
early tomorrow AM, and do have a patchy mention going east of HWY
281 after collab with neighbors. The best potential for more
impactful fog looks to remain across central/eastern KS.

Have the remainder of the forecast dry from mid-morning tomorrow
through tomorrow night, though will have to keep an eye on the
potential for some peak-heating-mid-afternoon isolated precip,
mainly across far western areas. This disturbance moving through
tonight will push a sfc frontal boundary through the area,
ushering in westerly, then northwesterly winds by mid-morning
tomorrow. Expecting breezy conditions to develop in the wake of
the front through the afternoon, gusts around 25 MPH are likely
for most locations. Speeds will taper off tomorrow
evening/overnight. A cooler air mass will begin sinking south into
the area tomorrow, and though highs should still reach into the
mid 40s to lower 50s, with gusty winds it`ll feel notably cooler
(esp across the northern half of the CWA).

.LONG TERM...(Tuesday through Sunday)
Issued at 318 PM CST Sun Feb 16 2020

Uncertainties in the forecast continue right into the Tuesday-
Wednesday time frame, mainly regarding precip chances. The next
upper level shortwave looks to move into the area Tuesday-Tues
night, but there isn`t great model agreement with how much/if any
precip the CWA sees out of it. Current forecast keeps the daytime
hours on Tuesday dry, with the better chances just outside our
W-SW border. Models have gone back and forth with this timeframe a
bit...so confidence remains pretty low. The better chances for
precip have become more focused on the Tuesday night-Wednesday
night time frame, with models the last in this series of
disturbances swinging through the Plains. Latest run of models
ramping up chances mainly during the daytime hours on Wednesday,
as the disturbance moves in and increase mid-level convergence
occurs. There is better agreement with reinforcing shots of colder
air keeping precip during this time, keeping things as snow. Hard
to get too hung up on precip amounts with this still a couple
days away, but if current model trends hold, a few inches of snow
will be possible, esp across northern and western areas. Still
plenty of things to iron out.

Once this system pushes out of the area, the forecast is dry for
Thursday through at least the first half of the weekend, as upper
level ridging builds in from the west. More uncertainty arises
once again just beyond this forecast period on Sunday.

As far as temperatures go, the colder air mass building in looks
to drop highs for Tuesday into the 30s/low 40s, and Wednesday
currently expected to be the coldest day, with forecast highs in
the mid 20s to mid 30s. Should see a gradual warm up then through
the end of the week, with Saturday forecast highs back in the 50s.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 710 PM CST Sun Feb 16 2020

General overview:
High confidence that the vast majority of the period will feature
VFR ceiling/visibility, with about the only question mark being
whether at least a brief/fleeting MVFR ceiling might develop late
in the period on Monday afternoon. Precipitation-wise, there is
roughly a 5-hour window-of-opportunity tonight for possible
passing sprinkles/light rain, so have introduced a basic "VCSH"
from 04-09Z to account for this. As for winds, fairly light speeds
(under 10KT) will prevail overnight into the first part of Monday
morning, as direction gradually transitions from more southerly to
more westerly. However, a decent uptick in speeds will arrive by
mid-late morning behind a passing cold front, with especially the
17-23Z time frame dominated by sustained northwest speeds around
17KT/gusts to around 24KT.

Additional notes regarding ceiling trends/uncertainty:
Much of the period will feature plentiful mid-high level cloud
cover, but with high confidence that ceiling remains solidly up
into the 5-10K ft. range. However, especially for Monday
afternoon, there are hints that at least scattered MVFR clouds
will materialize, with at least some potential for a broken lower
cloud deck. Given this possibility is currently fairly low-
confidence and is well beyond the first 12 hours, will maintain
VFR for now but at least "hint" at the MVFR possibility with a
"SCT030" mention.

&&

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

$$

UPDATE...Pfannkuch
SHORT TERM...ADP
LONG TERM...ADP
AVIATION...Pfannkuch

NWS GID Office Area Forecast Discussion