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000 
FXUS63 KGID 301813
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
113 PM CDT Sun Apr 30 2017

.UPDATE...
Issued at 1157 AM CDT Sun Apr 30 2017

Within the past 1-2 hours, have made some adjustments to snow
totals and also headlines, attempting to take into account what
has happened so far today. To summarize: 
1) Have maintained a Winter Storm Warning for our 6 southwestern-
most Nebraska counties where a decent coverage of 3-6" is still 
anticipated. Especially Furnas County is prone to higher totals as
we have already received a report of around 5" near Wilsonville. 
Clearly the highest anticipated swath of snow appears to focus 
from Furnas County and into adjoining counties.
 
2) Outside the Warning area, have generally tweaked down totals 
at least slightly, especially in our far north around 
Valley/Greeley counties. As a result, a handful of counties mainly
in our far north along with western portions of North Central KS 
were "downgraded" to a Winter Weather Advisory from Warning. This 
still means that it could get dicey for a time in any Advisory 
counties, but the overall lower expected snow totals are more 
representative of an Advisory situation than a warning. The
eastern edges of the Advisory (such as Adams/Hall) are probably
rather marginal to even stay in an Advisory, but at least parts 
of these counties could realize up to a few inches later this 
afternoon/evening as eventually precip type is expected to 
transition from rain. 

In summary, our highest confidence in widespread impacts clearly
focuses in the 6 Warning counties (especially Furnas area), but as
with any storm in progress (especially one with occasional
lightning/embedded thunder indicative of a little elevated
instability), later "curveballs" are possible and will again 
hopefully be able to better account for any of these when the 
main afternoon forecast "package" comes out in around 4 hours.

UPDATE Issued at 617 AM CDT Sun Apr 30 2017

11Z observations and web cams indicate a transition to snow in the
Holdrege and Lexington areas with light snow starting to
accumulate. Temperatures in the areas with snow are around 33F to
34F. Snow is also being reported in Mccook/Hill City areas with
precipitation falling as rain farther east.

&&

.SHORT TERM...(Today and tonight)
Issued at 430 AM CDT Sun Apr 30 2017

It's a complicated short term weather forecast as an upper low 
pressure system in the Texas panhandle lifts northeast through 
Oklahoma into south central Kansas and then tracks into northeast
Kansas today/tonight. Widespread rain has developed with this 
system across our area in good dynamics/isentropic 
lift/frontogeneis. So far the precipitation has been predominately
rain overnight, however we have had a few reports of snow mixing 
in at times, and even had a period of rain/sleet at our office.

Models remain consistent with the track of the system bringing 
additional widespread precipitation across our area today and 
through the evening before winding down tonight. Precipitation 
type however is not clear cut. Much of the precipitation through
the first part of the day will mainly be rain and some of the
short term models suggest the potential for sleet versus snow at 
times, which would limit snow amounts, and models have also slowed
the timing of the rain mixing with or changing to snow. Snow 
accumulations (of any significance) are no longer expected by 
daybreak with only a few areas in our west seeing accumulating
snow during the morning. Because of this have had to lower the 
predawn and morning snowfall amounts which have ultimately lowered
the expected storm total snow.

As the upper low lifts northeast today, a snow band is still 
forecast to develop across our western zones which will shift 
northeast with time as the upper low lifts into northeast Kansas. 
Have kept our current headlines as is for now due to the potential
of a rain/sleet/snow mix at times this morning, with the better 
chances for accumulating snow arriving later this afternoon and 
evening. Within a snow band later today, and if the thermal 
profile remains supportive, have a wide range of 3-8 inches of 
snow possible. Outside the snow bands, lesser amounts are 
forecast. Confidence on snow totals remain low due to temperatures
remaining above freezing. 

Also of note is that mesoanalysis indicates that instability is 
not zero and we have had a few reports of thunder in the vicinity 
of our cwa overnight. Have not included thunder in the forecast, 
but would not be surprised to see a little lightning.

Look for winds will remain strong and gusty all day and into the 
first part of the night before beginning to subside in a still
tight pressure gradient. North winds of 25 to 35 mph will be the 
rule with gusts of 45 mph. The strong winds combined with any snow
will cause restrictions in visibilities and make for difficult 
travel. As the system lifts out tonight the snow will end west to 
east. Currently have low temperatures forecast in the low/mid 30s
which is cold heading into the first of May. Have not included
frost in the forecast due to the steady wind speeds but those with
sensitive outdoor vegetation should be aware that temperatures 
will be cold.

.LONG TERM...(Monday through Saturday)
Issued at 430 AM CDT Sun Apr 30 2017

At the start of the long term period Monday morning, models are in 
good agreement the main upper level low pressure system having 
shoved off to the east, set up over central portions of IA by 12Z. 
Through the morning hours Monday, lingering PoPs remain across far 
northeastern portions of the CWA, as precipitation continues to wrap 
around the backside of the low. The afternoon hours remain dry, but 
confidence in that isn't the highest, especially in WNW portions of 
the CWA, with some models showing the potential for some additional 
light precipitation nosing in with an upper level jet streak. At the 
surface, the pressure gradient is finally starting to diminish as 
the main low slides further away, but breezy northwesterly winds are 
expected through at least the first half of the day. Confidence in 
high temperatures isn't the highest, as how today pans out 
(accumulating snow) will play a big part. At this point have lower to 
mid 50s across the WNW half, with near 60 in the SE.

Have the dry forecast continuing into Monday night and the morning 
of Tuesday, but another disturbance looks to bring precipitation 
chances to the area Tuesday into Wednesday. This lower amplitude 
shortwave disturbance is shown by models to move in with the 
northwesterly flow in place, with the better chances coming after 
00Z Wed. More of the focus looks to be south of the CWA, with more 
scattered QPF shown by models, so PoPs are in generally in the 20-
40% range. With little/no instability around, kept any thunder 
mention out of the forecast. A weak surface pattern looks to keep 
winds on the light side Tues/Tues night, with a reinforcing shot of 
northwesterly winds for Wed (though speeds even then aren't notably 
higher). High temperatures for both days are in the lower 60s.

Thursday and on through next weekend, the forecast remains dry. As 
the midweek disturbance moves out of the area, it continues digging 
southeast, developing into a closed low. To the west, ridging is 
building north, as another storm system approaches the west coast. 
This ridge will slide east onto the Plains, with the latest run of 
models showing the main axis overhead this weekend. Will see if 
model trends stick with that. Expecting highs to rebound back into 
the 70s by Fri.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Monday afternoon)
Issued at 113 PM CDT Sun Apr 30 2017

The bottom line is that a major mid-spring storm will continue 
impacting both KEAR/KGRI through especially the first 18 hours or 
so. Ceiling is expected to remain solidly IFR /low-end MVFR 
through this time, with visibility largely sub-VFR but likely 
varying considerably based on the intensity of precipitation at 
any given time. Speaking of precipitation, especially KEAR will 
likely see prevailing light to moderate snow, although it could 
mix rain or even sleet at times. KGRI will hold onto prevailing 
rain longer but should also become prevailing snow at some point 
later this afternoon/evening. Actual accumulation of wet/slushy 
snow is very tricky but am generally expecting 3-4" at KEAR and 
1-2" at KGRI, but could foresee higher than this at KEAR. 
Precipitation will gradually diminish/end overnight and am 
tentatively aiming for a return to VFR ceiling at KEAR by 13Z and 
KGRI by 15Z. 

The other main story will be rather strong winds, gradually
transitioning in direction from northerly to northwesterly. A 
slight decrease in wind speeds is possible with time, but in 
general, gust potential in the 25-35kt range will persist
throughout. 

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Warning until 6 AM CDT Monday for NEZ060-061-072-
     073-082-083.

     Winter Weather Advisory until 6 AM CDT Monday for NEZ039>041-046-
     047-062-074-075-084-085.

KS...Winter Weather Advisory until 6 AM CDT Monday for KSZ005-006-017.

&&

$$

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