This mornings forecaster discussion.
Short term...
today and tonight...
will need to keep this short due to the complicated nature of this
forecast cycle. All models continue to indicate a near bomb low
pressure coming through Missouri to reach Chicago by late Thursday
afternoon. Today is benign...with clouds and seasonal temperatures
for the most part...though a few degrees above normal. Highs in the
middle 30s north to lower 40s south with strengthening east winds to 15
miles per hour during the day.
Tonight...there is still much disagreement on low level thermal
parameters...with two model clusters on 850/925mb temperatures. The
NAM/high res nmm/high res arw/European model (ecmwf) all show the rain to snow line /
0c or slightly colder at said levels...to be from Fairfield to
Moline...to Sterling Illinois. The GFS and UKMET are warmer...with this
line up to Iowa City to Stockton Illinois...from 06z all the way to 12z
before crashing southeast. Thus...there is still uncertainty on
ptype overnight. The milder GFS/UKMET will hammer the northwest 1/3
of the County Warning Area with heavy snow...as does all other model guidance.
Liquid quantitative precipitation forecast of 0.5 to 0.7 is likely tonight in most locations...and
northwest of a Ottumwa to Iowa City to Galena line...this should
fall has heavy snow. Winds...especially after 06z will become very
strong from the north/northeast over the heavy snow areas...and
blizzard conditions will develop. A Blizzard Warning will be issued
for much of east central Iowa and northeast Iowa...as well as Jo
Daviess County...though mainly for the impacts in northwest sections
of that County. Overnight snow totals of 5 to 9 inches appear
likely northwest of that line...with the event peaking after 12z
Thursday. For locations just southeast of this line...including
Mount Pleasant through the quadrant cities...to Freeport...a challenging
mix of rain/rain and snow mix/possible sleet and thunderstorms are
possible. And if the first model cluster of lower level thermal
parameters are correct...this axis could see significant snow
overnight as well. For now...will be conservative and hold off on
any overnight headline and have a sharp cut off on snow
accumulations to zero southeast of Burlington to Moline...to
Sterling. Rainfall may cut off for a while after 06z Thursday in the
southeast as a dry slot begins to move up into Illinois.
After 00z...the combination of heavy snow and increasing blowing
snow...will cause major travel hazards in east central Iowa as we
approach 06z. After 06z...strong winds...heavy snow...Gravity
waves and thundersnow are possible. All of these features lead US
to start and end the event with one Blizzard Warning in those
locations...while others seeing the event mainly during the day
Thursday remain free of overnight headlines. Ervin
Long term...
Thursday through Tuesday...
forecast focus on major winter storm on Thursday then dry but cold
through the weekend. Low confidence on next week's storm system.
Thursday and Thursday night...major winter storm centered near
Quincy at 6 am Thursday will be tracking to SW lower Michigan by evening.
As the cyclone moves east the rain/snow mix roughly near and east of
the MS river early in the morning will be changing over to heavy
snow at most locations later in the morning...continuing into the
afternoon. West of the MS river heavy snow will be ongoing in the
morning then gradually diminishing in the afternoon. Combine that
with 50-55+ miles per hour wind gusts and life threatening blizzard conditions
will be occurring most areas on Thursday. With these intense
cyclones there could also be Gravity waves that develop for brief
periods and cause 60+ miles per hour wind gusts.
Snow totals from Wednesday evening through Thursday evening will
range from 12 to 16 inches across portions of northeast Iowa and far
northwest Illinois to 2 to 4 inches in our far southeast County Warning Area. Will linger a chance of
light snow in our far eastern counties Thursday evening but areas of
blowing snow will continue cwa-wide. Later Thursday night the
winds/blowing snow will be diminishing. Temperatures will be likely
falling from early morning highs on Thursday. Lows Thursday night will
plummet into the single digits especially where the deepest snow
cover will be.
Friday through Sunday...after the passage of the major storm system
operational models quickly return a zonal flow to the Midwest.
Typically this would bring milder air but with deep snow cover in
place temperatures will be cold. Will forecast maximum temperatures only in the
20s where the deepest snow will be to the lower to middle 30s far
south. Lows will be in the single digits north to teens south.
Early next week...low confidence in the handling of potentially
another winter storm around Christmas. While earlier model runs were
indicating a snow storm in the Midwest the European model (ecmwf)/GFS 00z run has
greatly diminished this threat...taking the storm south and east of
the dvn County Warning Area. However...we have seen this picture before and later
model runs may return the snow storm to the Midwest after all. For
now will continue with chance probability of precipitation. Stay tuned.
jimhardyOriginal Author
islandbreeze
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