Area forecast discussion
National Weather Service Hastings NE
1103 am CDT sun may 19 2013
Update...
issued at 1103 am CDT sun may 19 2013
Forecast is now in the basic form it will have at 4 PM this afternoon. Only
minor enhanced short-term forecast /estf/ adjustments will be needed
in the very short-term /3-6 hrs/. The main changes were to lower
probability of precipitation substantially 12am-12pm Monday...essentially trending the forecast
to dry. Also withdrew thunder during this time frame. With the
developing cut-off low north of the forecast area...precipitation will be diurnally
driven.
12z soundings: the atmosphere has overturned from 00z to 12z at
lbf/oax. The low-levels are substantially drier as a result. Models
are not capturing this well which is not surprising given
limitations of convective parameterizations. However...this
influences what the models believe will occur later today.
Dewpoints this afternoon were lowered west of Highway 281 as drier air will mix
down.
Mesoscale-analysis shows the weak cool front from Osceola Nebraska-Stockton
Kansas. The 12z oax sounding shows a substantial cap around 850 mb with
no cap on the lbf sounding. So the front is cooling the low-levels and
there should be no cap by late morning.
Thunder: convective overturning has cooled the lower half of the
troposphere. This will result in less cape and a skinnier cape
profile. At best believe MLCAPE will maximize around 1200 j/kg...
with temperatures in the middle-upper 70s and dewpoints in the low-middle 60s /E of
Highway 183/. Low-level winds will be substantially weaker than
yesterday...and middle-level winds will weaken through the day...
decreasing from 30 to 15 kts from NW-se.
Storm movement: north-northeast 15-30 kts...fastest southeast of the Tri-Cities and
slowest northwest.
Individual storms should cluster into multiple short line segments
with predominantly multicell character.
Severe: overall threat looks marginal and mainly east of Highway 81.
Continued middle-level cooling /as upper trough moves in/ suggests 1" hail
will be the main threat...but sub-severe hail will probable dominate.
Initial assessment of the environment suggests we/ll warn on 50
dbz to 25k feet and 60 dbz to 19k feet. With upper low closing
off...cyclonic flow...little cinh and decent 0-3 km cape...we/ll
be watching for possibility of a non-supercell tornado though this
will be a very low probability.
&&
Short term...(today and tonight)
issued at 415 am CDT sun may 19 2013
Not a straight forward forecast for today as a cold front extends
from a surface low across South Dakota down to a dryline near the
panhandles of Texas and Oklahoma. While precipitation surrounds
much of the forecast area early this morning...our coverage area
remains nearly precipitation free at the moment after a line of
strong to marginally severe thunderstorms crossed the forecast
area late Saturday evening.
While short term guidance is not capturing current precipitation
trends particularly well...expect the cold front across western
Nebraska early this morning to eventually begin to push eastward
by late morning or early afternoon. This cold front is expected to
be the trigger for additional thunderstorm activity across the
region as we head towards the afternoon hours...and has already
been responsible for a few severe thunderstorms across eastern
Colorado and western Kansas early this morning. While widespread
severe weather is not anticipated...the local area remains in a
region highlighted for a slight risk of severe weather by the
Storm Prediction Center...and with plenty of instability and an eroding cap...expect
the potential for some severe storms to develop during the late
morning through early evening hours. While there is some weak
shear...the primary threat with any severe storms that do develop
will be large hail and gusty winds.
Otherwise...went ahead and lowered the maximum temperatures for
this afternoon as ample cloud cover should help hold down
temperatures a few degrees from previous forecast...with the
approaching cold front steering a cooler airmass into the local
area by afternoon. Precipitation is then expected to taper off
this evening...however with the surface low meandering to our
north...cannot rule out a few additional showers wrapping around
this area of low pressure during the overnight hours.
Long term...(monday through saturday)
issued at 415 am CDT sun may 19 2013
The week ahead will be somewhat unsettled and generally cooler
than the previous few days...although averaging out to be still
near normal temperature wise.
Monday through Wednesday...the Central Plains will be influenced by
cyclonic flow around a slow moving upper level low pressure...
forecast to move from South Dakota on Monday to the western Great
Lakes by Wednesday. Monday is probably the best day of the
three...as the upper low spins further north and allows for more
sunshine across much of the forecast area...and a west/southwest
wind most of the day. Later in the day...clouds will thicken from
the northwest and that will eventually lead to cooler weather
Tuesday and Wednesday. Rain chances will be small and scattered
throughout the Monday-Wednesday time frame...all the while favoring
the northern parts of the region as opposed to the south. None of
the precipitation in this period looks to be much more than light at
best.
Wrapping up the week...Thursday looks like a mostly dry day and
a little warmer as upper level ridging tries to take hold. By
Thursday night and Friday...models have been fairly consistent in
the last few days with weak energy cutting through the center of the
ridge aided by a broad zone of moisture return...warm advection and
isentropic lift. Forecast reflects scattered precipitation chances
going into Friday and that looks on track from the Point of View of
several models. Too early to attempt to fine tune any details. Just
beyond this forecast cycle...it looks like the Memorial Day weekend
may start out on the damp side Saturday...with temperatures near
normal. Sunday and Memorial Day hold the best potential for
temperatures sneaking up and the region catching some decent Holiday
weather for outdoor activities.
&&
Aviation...(for the 12z kgri taf through 12z Monday morning)
issued at 545 am CDT sun may 19 2013
While prevailing VFR conditions are expected at kgri through the
period...cloudy skies and the potential for some isolated strong
to severe thunderstorms will be possible as well. Winds today will
remain light and variable through the morning hours...before
gradually shifting an becoming westerly late in the day behind a
slow moving cold front. While prevailing VFR conditions are
expected...brief MVFR or even IFR ceilings and visibilities will be possible
with any thunderstorms that do clip the terminal.
&&
Gid watches/warnings/advisories...
NE...none.
Kansas...none.
&&
$$
Update...halblaub
short term...sar
long term...Moritz
aviation...sar
