Area Forecast Discussion
Issued by NWS Hastings, NE

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KGID 292121

Area Forecast Discussion
National Weather Service Hastings NE
421 PM CDT FRI JUL 29 2016

.SHORT TERM...(This evening through Saturday night)
Issued at 422 PM CDT Fri Jul 29 2016

These next 36 hours are highlighted by continued, fairly low-
confidence thunderstorm chances and by a continuation of at least
slightly below normal late-July temperatures. As for severe storm
chances, in theory our risk is rather low, but it is certainly not
"zero" either. Right away this evening/tonight we will have to
keep an eye on mainly our western zones for perhaps a few strong
storms, and then even more-so late Saturday afternoon-Saturday
night for another possibility of perhaps a few severe storms.
Officially, the latest SPC Day 2 outlook barely clips our far
western CWA with a Marginal Risk, but based on combos of
CAPE/shear and also the latest 15z SREF calibrated severe storm
probability, would not be surprised to see this Marginal expanded
to include somewhat more of the CWA on upcoming outlooks.

A quick look at recent/current weather:
Today has clearly come to fruition as likely being the overall-
coolest day of the next week and beyond, as most of the CWA is on
track to only top out in the 78-84 range under partly to at times
mostly cloudy skies. In the mid-upper levels, we remain under
seasonably-strong northwest flow aloft, with water vapor imagery
revealing a series of low-amplitude shortwave troughs working
through the flow. One of these waves is currently departing
through the NE/KS/MO border area, and in combination with
unusually cool air aloft (evidenced by 700 millibar temps
generally 6-9C) and modest mixed-layer CAPE up to perhaps 1000
J/kg has sparked a smattering of mainly isolated, hit and miss
showers and weak storms that have drifted from north-to-south
across parts of the CWA throughout the day. Meanwhile, an upstream
wave and higher instability in a weak upslope-flow regime over the
Central High Plains is sparking a new round of strong/severe
storms still well to our west over western NE. At the surface, the
pressure gradient remains very weak with modest high pressure in
place, promoting very light breezes of no more than 5-10 MPH in
most places and generally from some variation of easterly.

Now briefly looking ahead forecast-wise through these next 3
forecast periods:

This evening/tonight:
As has been the case all-too common of late, even at this short
time range various deterministic/higher-res models are at odds
over thunderstorm chances. However, taking a general consensus of
things, have maintained at least low-end 20-30 PoPS across the
entire CWA, but with the higher values focused late tonight in
western counties. For late this afternoon/early evening, small
PoPS are mainly tied to the very hit-and-miss, mainly diurnally
driven (daytime heating) ongoing activity. But then this
evening/later tonight, the combination of storms possibly moving
in from the west and/or new development flaring up within a modest
low level jet axis could promote somewhat greater coverage,
especially within our western counties. At this time, we remain
well-outside the official SPC Marginal Risk area as instability
values should drop off quite a bit if/when storms eventually
arrive into our area from the west, but this types of upper air
pattern sometimes yield "surprises", and we will have to keep an
eye out for perhaps a few stronger storms. Otherwise, generally
very light east-southeast breezes tonight with low temps aimed
into the 60-65 range most areas. Although left any formal patchy
fog mention out tonight, suppose it cannot be completely ruled out
on a very localized basis.

Saturday daytime:
Overall, expect the majority of the CWA to remain dry the majority
of the day, but enough uncertainty exists that with the exception
of far eastern zones during the afternoon, a slight chance PoP has
been maintained for the entire day. In the morning, could easily
see some isolated activity lingering over from late tonight. Then
by late afternoon, considerably higher instability/CAPE values are
anticipated especially in our western/southern zones thanks in
part to warming low-level temps and increasing surface
moisture/dewpoints. Although it is no certainty that storms will
form during the afternoon (pre-7 PM) period, if they do, a late
afternoon severe threat may not be out of the question in
western/southern counties. Under generally partly cloudy skies,
high temps are aimed roughly 5 degrees warmer than today, with
mid 80s prevalent in NE and upper 80s in KS. Although not truly
windy by any means, southeast breezes of generally 10-15 MPH will
be more noticeable as the day wears on.

Saturday evening/night:
As noted in the opener, am wondering if maybe our risk of at least
strong, to perhaps marginally severe storms may not be fully
captured by the current SPC Day 2 outlook. Even if late afternoon
strong/severe storms fail to develop, the overnight hours
look supportive of possibly a few separate areas of storm
development, some of which could be strong to severe. For one,
High Plains convection could again roll in from the west-
northwest. In addition, there are hints of low-level jet induced
storms to perhaps blossom mainly within the southeast half of the
CWA. We will obviously be refining PoPS/severe chances as this
period nears. Temp-wise, lows look to hold up a touch milder than
tonight with mainly mid-upper 60s.

.LONG TERM...(Sunday daytime through Friday)
Issued at 422 PM CDT Fri Jul 29 2016

General overview of this 6-day period:
Although most of these day/night periods are littered with
various, mainly low-confidence chances for showers/thunderstorms
(PoPs), the overall "biggest" story of next week will likely end
up being a roughly 4-day stretch of solidly above-normal heat
centered from Sunday-Wednesday, and perhaps peaking in intensity
on Monday. Compared to our blast of heat a few weeks ago, this one
does not look as long-lasting or intense (more in the way of highs
in the mid-upper 90s versus near 100), but nonetheless a good
reminder that summer is still very much here. Although confidence
in the details obviously lowers with time, a modest cool-down back
into highs more into the 80s/low 90s is preliminarily anticipated
for late next week. In the basics of the mid-upper levels, most of
these 6 days features a fairly typical summer quasi-zonal
(generally west-to-east) flow pattern with some periods of
southwesterly flow possible later in the week as well. Very
generally, our area remains within the "in between zone" between
the stronger flow traversing the far northern CONUS and the
weaker/broad ridge flow dominating the southern CONUS.

Additional comments focused on thunderstorm chances/PoPs:
Overall, no major changes were made versus previous forecast.
Taking precip chances literally, our overall-highest PoPs of 30-40
percent are focused on Saturday night, and then again later next
week during the Wednesday night-Thursday night time frame.
However, please don`t "turn your back" on all of the various,
slight/20 percent chances also lurking in there, as these could
easily turn into something more as details become clearer. As for
severe weather chances, nothing really stands out as
"obvious"/widespread at this time, but that doesn`t mean that one
or two isolated/localized events might not eventually transpire.

Additional details regarding temps/heat index concerns:
Given that we mention near-advisory heat index of 100+ in our
Hazardous Weather Outlooks (advisory criteria technically starts
at 105+), we are highlighting the entire Sunday-Wednesday time
frame in the latest HWO. On Sunday, 100+ values look to remain
confined to KS zones, but then expanding northward to also include
various parts of Neb zones Mon-Wed. Although the details are far
from set, the overall worst heat is currently slated for Monday,
when some places could reach 105 heat index values assuming that
dewpoints don`t mix down more than anticipated.


.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Saturday afternoon)
Issued at 1230 PM CDT Fri Jul 29 2016

Confidence is reasonably high in VFR ceiling/visibility through
the period, along with rain/storm-free conditions the vast
majority of the time. Unless convective outflow disrupts the mean
surface flow for a time, winds should average under 10kt through
the period with direction generally from some variation of
easterly. Now for a few possible exceptions/caveats worth

Right away this afternoon, a brief MVFR ceiling is certainly
possible for a few hours, but will maintain a low-end VFR ceiling
for now. Visibility-wise, cannot rule out some light fog during
the overnight/early morning hours but will only "hint" at this
with a low-end VFR "6SM BR" mention.

While a rogue shower/non-severe storm is almost impossible to rule
out any point during the period, latest radar trends clearly show
these first few hours stand a decent chance of some off-and-on
activity. As a result, will carry a generic "vicinity" (VCTS)
mention for this afternoon and maybe even a brief TEMPO group,
but will leave out any shower/storm mention beyond that due to
lack of confidence in occurrence.


.GID Watches/Warnings/Advisories...


SHORT TERM...Pfannkuch
LONG TERM...Pfannkuch
AVIATION...Pfannkuch is the U.S. government's official web portal to all federal, state and local government web resources and services.