Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
FXUS63 KDVN 282100
Area Forecast Discussion
National Weather Service Quad Cities IA IL
300 PM CST Mon Nov 28 2016
Issued at 257 PM CST Mon Nov 28 2016
The latest sfc analysis was indicating the main frontal boundary
stretching from north-to-south acrs central IA, with lingering tight
southeast flow gradient just to the east of it acrs the local area
driving blustery sfc winds of 15-25+ MPH. Also, areas of showers
with some embedded thunder continued to stream up the CWA from
north to south. Rather low cloud cover and rain again limiting the
high temp potential for this afternoon acrs much of the area. Aloft,
the closed upper low center was seen on the latest water vapor loop
spiraling acrs extreme southeastern SD.
.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 257 PM CST Mon Nov 28 2016
Tonight...Will have to watch the western/northwestern CWA border
counties through at least 5 PM for the ongoing isolated to wdly
sctrd showers and storms to possibly flare up again along narrow pre-
frontal instability axis(tongue of 250-400+ J/KG CAPES) for isolated
high shear/low cape severe storm possibility. Like the previous shift
noted and the occurrence just upstream a few hours ago, hail and a
brief spin-up tornado the main threats from these cool season low
topped storm cells. Hopefully the time of day, the clearing
clouds/instability edge not really getting into the local CWA until
after dark and some signs of even the marginal instability upstream
waning some recently, will preclude this potential over the next 3
hours or so. But will have to keep it in mind if storms do indeed
increase in intensity some. Otherwise will walk out larger coverage
conveyor of showers and some embedded thunder along and east of the
MS RVR, off to the east eventually by mid evening. A few of these
areas east of the river may get up to an additional quarter of an
inch of rain before it ends from 00z thru mid evening, but most
areas that get in on lingering precip should get in the range from
0.05 to 0.10 after 00z.
With the main upper low axis expected to gyrate almost in place
overnight or barely edge eastward acrs NW MN, the upstream clearing
wedge/dry streak will eventually make it over portions of the CWA
this evening(maybe not east of the MS RVR til close to midnight).
Post-frontal SW flow will not really advect in much cooler air from
that source region area, but clear skies and drier DPTs may allow
for lows in the mid to upper 30s acrs much of the CWA by dawn Tue.
Mixing winds and if clouds maintain in some spots, those areas may
have trouble dipping out of the 40s.
Tuesday...With the main upper low slowly rolling eastward acrs
northern MN, much of the CWA should remain in the less cloud
affected dry slot for much of the day. But the wrap around cloud
deck now acrs the Dakotas and western MN will try to get into at
least the northwestern portion of the fcst area as the day
progresses. Otherwise, lingering mild air mass, some insolation and
mixing at least to H925 MB will make for unseasonably highs in the
low to mid 50s acrs much of the area. Even deeper mixing up close to
H910 would mean some upper 50s. But will play it conservatively for
now and just make minor adjustments to ongoing temps. ..12..
.LONG TERM...(Tuesday Night through next Monday)
ISSUED AT 257 PM CST Mon Nov 28 2016
Forecast focus on a cloudy and chilly remainder of the work week
with little if any precipitation. An active pattern then setting up
late this weekend and next week.
Tuesday night through Wednesday night: Upper level trough across the
Midwest/Great Lakes region will dominate the weather. Chilly air and
enough moisture in the column will make for a rather cloudy period
(typical this time of year). There will also be a small chance of
mixed precipitation, mainly our northern cwa, as several vort maxes
rotate around the upper system and move across the area. What
precipitation falls should be quite light and scattered and have
kept pops at 20-30 percent. Maximum temperatures will be close to
normal for late November, in the 40 to 45 range.
Thursday through Saturday: We start December with the upper level
trough shifting into the northeast United States allowing for
heights to rise. This should be a dry period with partly cloudy
skies. However, chilly air will be locked in place with highs
generally in the upper 30s to lower 40s and lows in the 20s to lower
Saturday night through Monday: This is when the weather pattern
begins to get much more active and wintry. However, confidence in
the deterministic models remains low regarding the track and timing
of systems. There appears to be (synoptically speaking) the
potential for several significant winter storm systems to impact
portions of the Midwest within the next 2 weeks or so. ECMWF
suggests a storm system developing Saturday night in the lower
Mississippi River Valley and tracking into the Ohio Valley on
Sunday. This is much farther east compared to the previous run and
only clips our eastern counties with snow. The GFS streaks some
light rain or snow with a weak wave keeping the main energy in
Texas. For now the consensus keeps small pops in the dvn cwa.
Dry on Monday as strong jet energy begins to carve out an upper
level trough in the Western United States. Highs will once again be
in the upper 30s to lower 40s with lows in the 20s to lower 30s.
.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
ISSUED AT 1143 AM CST Mon Nov 28 2016
Solid MVFR deck with areas of IFR this afternoon, with sctrd fast
moving showers and some thunderstorms streaming up quickly from
north-to-south ahead of an incoming front acrs western IA ATTM.
If a TAF site manages to get hit by one of the passing
thunderstorm cells, visibilties may be reduced temporarily down to
3-4SM by brief downpours and possibly embedded with small hail.
Clearing will try to move in from the southwest this evening and
overnight in the northern MN cyclone`s dry streak. Brisk
southeasterly sfc winds this afternoon gusting to 25-30 KTS at
times, will become more southwesterly later this evening and
diminish to 10-15 KTS into Tue morning. ..12..