Area Forecast Discussion
Issued by NWS Hastings, NE
FXUS63 KGID 301952
Area Forecast Discussion
National Weather Service Hastings NE
252 PM CDT Thu Mar 30 2017
.DISCUSSION...(This evening through Thursday)
Issued at 252 PM CDT Thu Mar 30 2017
Map analysis indicates a mid to upper tropospheric low over the
Missouri River Valley and a mid-tropospheric shortwave trough axis
over the northwestern CONUS. Subtle ridging is noted over the
Rocky Mountains, as well as another ridge over the Ohio River
Valley. Enhanced upper tropospheric jet energy extends from the
lower Mississippi Valley, north/northeast into the Great Lakes,
and then east into southeastern Canada and the northeastern CONUS.
Another area of enhanced upper tropospheric jet energy also
exists over the Pacific just off the northwestern CONUS coast. At
the surface an area of low barometric pressure exists over
northern Missouri. The surface wind across our area remains from
the north/northeast as a result.
Guidance suggests the mid-tropospheric low over the Missouri
River Valley will move east, away from the region tonight. The
mid- tropospheric shortwave trough axis over the northwestern
CONUS is expected to deepen into a closed low tonight, with this
low then expected to move southeast into the four-corners region
by 12Z Friday. This mid-tropospheric low is then expected to move,
slowly, to the east across the southern CONUS through early next
week. There are then indications of another mid-tropospheric low
moving into the central CONUS, perhaps impacting our area, during
the middle part of next week.
With the mid-tropospheric low over the Missouri River Valley
moving away from our area, an overall lack in omega should present
dry conditions to our area tonight through the day Friday.
Guidance does suggest a possibility of patchy fog development late
tonight into Friday morning as near-surface dewpoint depressions
drop to near zero and the surface wind field decreases. Given
this, went ahead with patchy fog across the area 09-15Z Friday.
Friday night through Sunday morning, thermal advection (ahead of
the next mid-tropospheric low moving across the southern conus)
could advance far enough north thus presenting enough omega for
precipitation production across our area. PoPs remain intact
across much of the area Friday through Sunday morning as a result.
Currently expect things to dry out and remain dry for most
locations Sunday afternoon through Monday, with the next chance
precipitation presenting itself starting Monday evening as the
next mid-tropospheric low approaches from the west. PoPs remain
intact next Monday evening through Wednesday as a result.
Guidance currently suggests meager lower tropospheric moisture,
along with less than impressive mid to upper-tropospheric lapse
rates, will promote little if any instability across much of the
area this weekend. There are some indications, primarily from the
NAM, that just enough lower-tropospheric moisture could work
northward thus promoting CAPE values of ~100J/KG across our far
south/southeast. So although a rumble of thunder cannot be ruled
out, the previous forecast did not have thunder and at this time,
there just is not enough confidence to introduce thunder.
Certainly something to monitor through the next few shifts. As for
the system mid next week, latest guidance suggest lower
tropospheric moisture will remain meager. And with different
solutions presenting varying positions of the mid-tropospheric
low, it`s too early to say whether the magnitude of mid to upper
tropospheric lapse rates will be sufficient to provide appreciable
instability across the area. Given this, went ahead and kept
thunder out of the forecast for next week as well, but also
something to monitor in the coming days.
Little change in the lower-tropospheric airmass suggests
temperature readings across the region will remain fairly similar
from day to day through mid next week, with highs generally in the
upper 40s to low 50s through Saturday, and then slightly warmer
with highs in the 50 to low 60s through the middle part of next
week. Lows during the forecast period are generally forecast in
the upper 30s to low 40s.
.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Friday afternoon)
Issued at 1213 PM CDT Thu Mar 30 2017
MVFR to IFR conditions expected through the next 24 hours.
Stratus is expected to persist at both TAF sites, near or just
above 1000FT AGL for the most part through this evening, and then
lowering below 1000FT AGL during the overnight hours. Visibility
is also expected to drop tonight, generally into IFR levels. The
surface wind will remain from the northeast during much of the
forecast period, starting off near 12KTS with locally higher gusts
this afternoon, then decreasing to around 06KTS tonight.