Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 270859
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
359 AM CDT Thu Apr 27 2017

.SHORT TERM...(Today and tonight)
Issued at 356 AM CDT Thu Apr 27 2017



.LONG TERM...(Friday through Wednesday)
Issued at 356 AM CDT Thu Apr 27 2017

The main story this forecast period is the increasing and high
likelihood of widespread precipitation a couple of different times
through Sunday night, with the potential for snow, especially late
Saturday night through Sunday night.

Friday through Monday. First, high temperatures will be below
normal through the period, and could be as much as 30 degrees
below normal Sunday. There will be some rebound Monday but still
below normal for May Day.

On Friday, we walk into the day with a fairly large band of light
rain ongoing. The precipitation is associated with a weakening
mid/upper level wave pivoting its wave across the area. Initially
frontogenetic in nature, the system weakens and becomes
frontolytic aloft by late in the day. That results in the rain
area starting to diminish by late morning and continuing the trend
in the afternoon. Weak surface low and boundary in Kansas could
spark a couple of afternoon showers in southern areas but that
shouldn`t be too widespread as the upper system weakens and more
of an open wave. Despite this daytime diminishing precipitation
trend with time, additional rainfall during the day averaging on
the 0.20" to 0.40" range is likely, with the heavier amounts
favoring south central Nebraska north of Highway 6/34 and west of
Highway 281.

Friday night should bring a temporary break to precipitation as we
await the influence of the main weekend storm system.
Precipitation chances are lower, but north central Kansas could
start to see more steady precipitation toward dawn Saturday. The
trend of a gradual feed of moisture and precipitation ahead of an
upper level low will continue all day Saturday. Far northern parts
of the forecast will be the last for precipitation Saturday and
may be dry much of the day, while north central Kansas could
easily see rain showers on/off all day.

Frankly, the main show and most intriguing part of the forecast is
late Saturday night, Sunday and Sunday night. All models are in
agreement with a rapidly deepening upper level low pressure
expected to move from the Texas panhandle to south of Des Monies
by Monday morning. 200+ decameter height falls with this system
thanks to a strong potential vorticity intrusion and 120-140KT
H250 jet wrapping around it. This will be a very potent system for
the region.

A few things stand out. One is the the wind by Sunday afternoon.
H850 winds of 50-60KTS are forecast and will likely see 25-35 mph
surface winds from the north by afternoon. Have increased wind
speeds Sunday.

Temperatures will also be very chilly and in the "record low high"
range Sunday for some locations. Lowered high temperatures Sunday
to the upper 30s some areas, and it may not be that warm.

Finally, precipitation looks plentiful, especially if the strong
deformation axis verifies as advertised Sunday and Sunday night.
After the initial rainfall Thursday night and Friday, the GFS,
ECMWF and Canadian are all very similar with heavy precipitation
Sunday and Sunday night. For the 48 hour period of Saturday 7 am
through Monday 7 am, additional precipitation ranges from 0.50" to
2.50+", with most of the area in the 1.50" to 2.50" range. There
will likely be spots in the forecast area, and it could be
several, which pick up 2 to 3 inches of moisture during the next 4
days.

With the precipitation and temperatures expected, snowfall comes
into play. Surface wet bulb and H850 temperatures suggest a high
likelihood of snow late Saturday through Sunday night.
Accumulation is on the table though its hard to say just how
much will accumulate right now. Stay tuned, but it could be a very
wintry scene for parts of the forecast area Sunday and Sunday
night. The system should be pulling out Monday. Right now we have
the forecast dry, but that might be a bit optimistic. Though
warmer Monday, its still chilly and likely breezy for a time.

Tuesday and Wednesday...the Central Plains region remains in
cyclonic flow in the wake of the large upper level low pressure.
Such a northwest flow will keep small chance for precipitation in
the forecast, especially later Tuesday and Wednesday. Though
warmer, I wouldn`t expect an big warming trend. Current forecast
of lower 60s could be on the high side if clouds are more
widespread and precipitation develops.

Though a bit beyond this forecast cycle, its worth noting an upper
level ridge appears likely late next week. So at least for a few
days, probably Thursday through Saturday (May 4-6), dry weather and
moderating temperatures appear in store for most of the central High
Plains.

&&

.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Thursday night)
Issued at 1217 AM CDT Thu Apr 27 2017

VFR conditions forecast through the majority of this TAF, with
deteriorating conditions possible in the final few hours of this
period. Surface high pressure over the region will continue the
light/variable winds through the early/mid morning hours, with
winds then turning east-southeasterly for the remainder of the
period. Speeds will remain on the lighter side. Precipitation
chances will be on the increase through the period, with the
better chances coming this afternoon/evening. Possible some
activity may move in before then, but not confident enough in that
timing to put in a mention at this point. Models showing in the
final few hours of the period that ceilings will be dropping to
MVFR.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Frost Advisory until 9 AM CDT this morning for NEZ060>064-
     072>077-082>087.

     Freeze Warning until 9 AM CDT this morning for NEZ039>041-
     046>049.

KS...Frost Advisory until 9 AM CDT this morning for KSZ005>007-
     017>019.

&&

$$

SHORT TERM...ADP
LONG TERM...Moritz
AVIATION...ADP


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