Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 300604

Area Forecast Discussion
National Weather Service Hastings NE
104 AM CDT Tue May 30 2017

.SHORT TERM...(This evening through Tuesday Night)
Issued at 251 PM CDT Mon May 29 2017

No significant weather impacts across the CWA today, with upper
air and satellite data showing northwesterly flow set up across
the Plains, in between low pressure spinning over the western
Great Lakes/Ontario area and ridging over the western CONUS. At
the surface, a weak cool front has been sagging south with time,
keeping winds across the CWA northwesterly, but winds are gusty
thanks to increased mixing. Sustained speeds are around 15 MPH,
gusts of 25 to 30 MPH. As far as temps/dpts go, another
comfortable day for late May, with dewpoints this afternoon really
mixing out, down in the mid/upper 30s for the majority of the
CWA, while temps for most are in the mid 70s.

Dry conditions remain in the forecast for this evening and for
most,  the overnight hours. Debated putting in some low PoPs for
central/southern portions of the CWA, with some models showing the
potential for some isolated activity roughly between 09-15Z
tonight/tom morning associated with some weak mid level
convergence and an upper level jet streak nosing in from the
northwest. Not all models agree with this, and many keep the
better chances for anything measurable just to the south of the
CWA. Decided to leave mention of measurable precip out at this
point due to lack of support from more models, and we are sitting
with a drier airmass in place, might be tough for anything more
than sprinkles to reach the ground. Will be something for the
evening/overnight crew to keep an eye on though.

As we get into tomorrow, though the morning hours, should anything
develop late tonight, it should quickly slide off to the east-
southeast, leaving behind dry conditions for much of (if not all
of) the day. At the surface, the pattern this evening/overnight
weakens, with light and at times variable winds looking to take
over the area. During the day tomorrow, models trying to show
another shot of northerly winds moving in as a more organized area
of high pressure builds south into the Dakotas. There is the
potential for a weaker surface frontal boundary to set up over
southern portions of the CWA tomorrow afternoon, providing a focus
for thunderstorm development. Models vary with exactly how things
would play out, as mid/upper level forcing is on the weak side.
Some of the 12Z runs aren`t much different with showing some
isolated/scattered activity late tomorrow afternoon, others have
dried out compared to the previous run or pushed just south of the
CWA. Will keep the inherited low PoPs going in the forecast
across north central KS for the mid/late afternoon hours. Should
storms develop, there will be some instability to work with,
though models vary with just how much. The NAM is on the higher
side, others are around 500-1000 j/kg which looks reasonable, and
with deeper layer shear around 40 kts, a strong/marginally severe
storm is not totally out of the question. Left the
evening/overnight hours dry, if storms were to develop, they
should push southeast fairly quickly.

As far as temperatures go, even though there is a weak front in
the area/high pressure pushing south into the northern Plains,
not really an accompanying push of cooler air. Models are showing
850mb temps a touch warmer than today, so am expecting temps
similar to/if not a few degrees warmer than today, have mid
70s/near 80 in the forecast. Overnight lows both tonight and
tomorrow night look to bottom out in the mid 40s to lower 50s.

.LONG TERM...(Wednesday through Monday)
Issued at 251 PM CDT Mon May 29 2017

At 12Z Wednesday, models are in pretty good agreement showing
continued northwesterly flow aloft, but with the Great Lakes low
moving further away, it`s not quite as amplified. To the west,
ridging remains in place, but to the southwest a disturbance is
pushing along the US/Mex border. At this point, the majority of
the CWA looks to be dry through the day, with focus on the
southwestern area. At the surface, generally easterly but light
winds start the day out, with high pressure looking to be centered
over eastern SD down along the MO river. Through the day, that
high continues sliding southeast, with broad low pressure off to
the west. Models are in pretty good agreement showing a warm
frontal boundary setting up during the afternoon roughly from the
southern NE panhandle southeast through central KS. There may be
the potential for a weak mid/upper level wave to move in from the
west-southwest, with this sfc front providing a focus for
thunderstorm development. Activity then looks to spread/move east-
northeast through the area during the evening/overnight hours,
along the convergence zone of an increasing southerly low level
jet. Instability should be better with models showing better
moisture/dpts into the 50s returning to the area, with deeper
layer shear around 30-40kts. Will again be the potential for some
strong/severe thunderstorms, esp early on across SWrn portions of
the CWA. Highs for Wednesday look to once again be well into the
70s/near 80.

Current forecast has Thursday/Thursday night dry, but confidence
isn`t the highest in it staying that way, mainly at the
beginning/end of this time frame. Questions lie with if any
lingering activity clips far eastern portions in the morning, and
whether the system moving out of the southwest will affect
southeastern areas. The majority of the daytime hours do look to
be dry. Winds look to turn more southerly across the area, as low
pressure remains off to our west. Forecast highs climb into the
mid 80s CWA-wide.

Friday and Saturday have the potential to be more unsettled, but
overall confidence in not high. Models still need to work out some
differences with the timing/locations of waved in the weak upper
level pattern that may be in place. The GFS is wetter than the
ECMWF. Highs remain in the upper 70s to lower/mid 80s. Models have
more agreement showing Sunday being dry and the forecast reflects
that, but hard to have any more confidence another day out when
there are plenty of things to iron out before then.


.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Tuesday)
Issued at 104 AM CDT Tue May 30 2017

Confidence is rather high in continued VFR ceiling/visibility and
precip-free conditions, with only limited mid-level cloud cover
at times. Any concentrated shower/thunderstorm activity that
might flare up during the afternoon within the region should focus
100+ miles off to the south/southeast of KGRI/KEAR. Surface winds
will average light/variable both early this morning and again late
in the period Tuesday evening. In between, especially the
afternoon hours could get a touch breezy from the northwest, but
even so, have backed off prevailing gust magnitude a bit from the
previous issuance, as expect peak gusts to average under 20kt for
the most part.




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