Area forecast discussion
National Weather Service Hastings NE
319 PM CDT Tuesday may 21 2013
Short term...(this evening through wednesday)
issued at 319 PM CDT Tuesday may 21 2013
Morning upper air analysis indicates a middle to upper level low over
northern portions of the Missouri River valley...with longwave
troughing over central portions of the Continental U.S....ridging over the
eastern Continental U.S....and another middle to upper level low approaching the
northwestern Continental U.S.. middle and upper level jet energy surrounds the
Missouri Valley middle to upper level low...and also extends from the
west-central Continental U.S. Into the southern Continental U.S.. all that being
said...middle to upper level flow is fairly weak over our
area...maxing out at around 35kts near 500mb per 12z sounding data
from klbf and koax. The strongest tropospheric flow over our area
is actually located within the lowest ~8000ft above ground level...with a wind
near 50kts indicated between 700 and 800mb. Water vapor imagery
clearly shows the middle level low over the Missouri River
valley...as well as the middle level low nearing the northwestern
Continental U.S.. at the surface an area of low barometric pressure exists
over the northern Missouri River valley...and a cold front extends
from northeastern Missouri into the Oklahoma and Texas. The low
level wind field across our area remains from the northwest as a
result.
A fairly strong low level pressure gradient...working in concert
with boundary layer mixing to around 800mb...has promoted a fairly
breezy day across our County Warning Area today. A few locations...primarily north
of Highway 6 and west of Highway 281...have periodically hit Wind
Advisory criteria. That being said...such observations have been
fleeting and no headline is expected through the remainder of this
afternoon given that the wind speed for these locations is so
marginal with respect to Wind Advisory criteria.
Dry conditions are forecast across the area through the next 24
hours with nothing in the way of high impact weather anticipated.
Guidance suggests the middle level low...currently over the northern
Missouri River valley...will continue moving east out of our area.
This should bring an end to any precipitation chances as upper
level ridging and an overall lack in kinematic forcing settles in
over the area heading into the day Wednesday. The cloud cover will
also be on the decrease from southwest to northeast across our County Warning Area
through the next 24 hours. Finally...a decreasing low level
pressure gradient should promote a weaker low level wind field
across our area through the next 24 hours.
Little change in the low level airmass would otherwise provide a
similar low temperature early tomorrow morning when compared to
this morning...but with cloud cover on the decrease...especially
across our southwest...it will more than likely be a touch cooler.
Given all this...went ahead with an overnight low temperature in
the middle to upper 40s across our County Warning Area. We have really struggled to
see any sunshine across much of our area today...but with
decreasing cloud cover and an increase in diabatic heating during
the day Wednesday...it seems logical that we ought to be somewhat
warmer during on Wednesday. An afternoon high temperature ranging
from the 60s to low 70s is currently forecast across our County Warning Area for
Wednesday as a result.
Long term...(wednesday night through tuesday)
issued at 319 PM CDT Tuesday may 21 2013
Wednesday night through Tuesday. Main forecast concerns will be
chances for thunderstorms Thursday night through Tuesday and
temperatures through the period.
Short wave ridging aloft and a surface high pressure system trying
to nose into the area will allow for dry conditions for Wednesday
night into Thursday. The surface high is a little on the cooler
side and low temperatures Wednesday night will be reflective of
that with readings only in the middle to upper 40s. By Thursday the
surface high will be moving to the east and winds will turn to the
south. With some sunshine...expect temperatures to warm to around
70 degrees.
An unsettled weather pattern will start to affect the area
Thursday night and continue through the period. The upper level
short wave ridge will be battered by several short waves spinning
off from an upper level low in the western Continental U.S.. models have some
differences in the strength and location of the upper level low in
the western Continental U.S....especially in the Monday and Tuesday time
frame.
The first of the waves to affect the area moves in Thursday night.
With the south winds the moisture increases especially on the High
Plains and some showers and thunderstorms are possible in the
southwest part of the forecast area Thursday night. The upper wave
and the low level moisture move off to the east Friday and Friday
night and bring chances for showers and thunderstorms to the area.
By Saturday a stronger wave moves into the area and with warmer
air pushing into the area the atmosphere destabilizes and MUCAPES
approach 4500 j/kg. This could lead to some stronger
thunderstorms. Another wave moves into the area on Sunday and a
warm front lifts north across the area. The warm air helps to
destabilize things further and MUCAPES over 5000 j/kg are expected
on Sunday. Will continue the threat of severe weather on Sunday.
The models have a few more differences by Monday and Tuesday. The
GFS has a stronger upper level low in the west than the European model (ecmwf) does
and has some stronger waves that move into the plains. With the
models having different solutions they still have some
precipitation around the area for Monday and Tuesday. Have kept in
some lower probability of precipitation. It certainly will not be raining all the
time...but there is some chances. The other consistency between
the models is that there is generally a broad ridge across the
region and temperatures will be on the warmer side.
&&
Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1215 PM CDT Tuesday may 21 2013
VFR conditions forecast until 02z...with MVFR conditions
thereafter.
Broken to overcast skies will continue at kgri through much of the
taf period...with guidance suggesting an MVFR ceiling will be
realized starting this evening and lasting into the morning hours
Wednesday...thus the MVFR forecast 02z Onward. The surface wind
will remain from the west/northwest through the taf
period...sustained near 19kts and gusting around 27kts this
afternoon into this evening before decreasing to around 12kts
tonight into Wednesday morning. Visibility restriction is not
expected at kgri through the next 24 hours.
&&
Gid watches/warnings/advisories...
NE...none.
Kansas...none.
&&
$$
Short term...Bryant
long term...jcb
aviation...Bryant
