Area Forecast Discussion
Issued by NWS Hastings, NE
FXUS63 KGID 241803
Area Forecast Discussion
National Weather Service Hastings NE
103 PM CDT TUE MAY 24 2016
Issued at 1104 AM CDT Tue May 24 2016
A rather substantial fcst update has been published thru 6 pm.
Environmental assessment is still on-going. But what we know is
that early morning tstms are departing to the E with rapid
clearing over all but the Srn fringe of the fcst area. Sfc
analysis shows a diffuse pattern with svrl mesoscale features...
the most prominent of which are the low over SW KS and the outflow
boundaries over Srn KS. There appears to be an old remnant portion
of the cool front from SW-NE across the Sandhills and then back
into SW Neb into NE CO.
Confidence in what transpires today is low. Model depictions of
what might develop vary wildly and are of little use. For what
Model fcsts of dwpts may be svrl degs too high compared to
sfc/upr air obs...and this will impact instability fcsts. The
models appear to be eroding the outflow boundaries and rapidly
advecting dwpts of 65-70F into the fcst area.
Another complication is that the morning tstms were at the Nrn
edge of the cap which was at +9C at 700 mb. This isotherm/cap is
fcst by the RAP to lift N to hwy 6 by 4 pm and I-80 by 7 pm. This
WAA can be see in the 00Z/12Z RAOBs at DDC.
For now...our current expectation is that a few tstms will
develop this afternoon/eve...with the best chance over S-cntrl
Neb. With temps near 80F and dwpts in the low-mid 60s and mid-lvl
lapse rates 7-8 C/km...MLCAPE will be 1500-2500 J/kg. Deep layer
shear will be sufficient (35-40 kts) for well-organized tstms.
Storm mode is also a bit uncertain...but it looks like primarily
multicell...but supercells cannot be ruled out either.
One final negative factor against tstm development...a lack of
forcing aloft. That could also keep tstm coverage rather minimal.
.LONG TERM...(Wednesday through Monday)
Issued at 529 AM CDT Tue May 24 2016
To make a long story short, the upper level longwave mean trough in
the western United States will persist through the long term as a
stationary or nearly stationary boundary hangs around or near our
area. Abundant moisture will be available as most people can tell by
the dewpoints in the 60s recently, so this means several days of
potentially inclement and severe weather, along with near normal to
a bit above normal temperatures. Highs will generally be in the 70s
and 80s and lows in the 50s and 60s.
.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Wednesday
Issued at 103 PM CDT Tue May 24 2016
Significant Weather: Sct IFR +TSRA. Potential for MVFR or IFR
stratus 09Z-15Z Wed.
This afternoon: VFR. Just a few altocu around 12K ft initially...
but sct cu should develop around 5K ft. A few IFR tstms could
develop nearby after 21Z. Winds are not behaving as model guidance
is expecting as the environment has been perturbed by tstm
activity. Winds could be anywhere between SSW-SSE 8-15 kts.
Tonight: VFR except in pockets of IFR +TSRA. There is some
potential for a bit of MVFR/IFR fog/stratus after 09Z. Winds
outside of tstms will be SE 5-10 kts. Confidence: Medium
Wed thru 18Z: Possibly MVFR/IFR fog/stratus to start. Any tstm
activity nearby should end early. Otherwise...VFR. Winds probably
SE 5-10 kts away from any tstm activity. Confidence: Low