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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
302 PM CDT Wednesday Apr 16 2014

issued at 300 PM CDT Wednesday Apr 16 2014

Conditions remain marginal for a red flag warning or even a Wind
Advisory at this time. No headlines expected. However...a couple
of observation sites have just managed to make it into the Wind
Advisory criteria this afternoon with sustained winds of 31 miles per hour
and gusts to 44 miles per hour. Relative humidiy remains above 30 percent.

Surface cyclone in extreme northwest Iowa continues to fill/weaken with
isallabaric analysis showing the best pressure falls in SW WI. Infrared
satellite loops indicate a classic mature comma head shape to this
middle latitude storm system across the upper Midwest. A strong vorticity
maximum was noted in extreme northeast Nebraska. All of the precipitation
is occurring on the cold side of the storm and mostly in the form
of moderate to heavy snow...from central Minnesota into northern WI.

In the warm sector the airmass was very dry thanks to a strong
high pressure ridge extending from the middle Atlantic to the Gulf of
Mexico. Surface dewpoints were only in the 20s and 30s all the
way from Iowa to Texas. There was also a tight pressure gradient with
winds gusting to 35 to 45 miles per hour across much of the County Warning Area. Current
temperatures were in the 50s.


Short term...(this evening through thursday)
issued at 300 PM CDT Wednesday Apr 16 2014

Forecast focus on slight chances of showers or sprinkles with
winds diminishing this evening. Temperatures a bit cooler on Thursday. the weakening/occluded cyclone pushes into central Wisconsin
the winds will slowly diminish as the evening progresses. Mesoscale
models arw/nmm indicate a band of very light showers or sprinkles
pushing into eastern Iowa later this evening due to positive vorticity advection arriving. However...
the precipitation will also fall apart of it pushes east of the MS
river due to the dry low levels. What little rain does manage to
reach the ground should only be a trace to .01 of an inch. With
south winds veering to the southwest to west later tonight temperatures
should remain milder than the past couple of night. I will forecast
minimum temperatures in the middle 30s to lower 40s. Only slight
chances in the grids in our northern County Warning Area closer to the strong vorticity maximum.

Thursday...with the passage of the weak cold front temperatures
will be somewhat cooler with highs in the lower to middle 50s. At
least the winds will be much lighter. There should be partly to
mostly cloudy skies as a secondary upper level trough rotates
across the region. Will have a slight chance of light showers late
afternoon in our far southern counties as a wave moves along the
front in MO.

Long term...(thursday night through wednesday)
issued at 300 PM CDT Wednesday Apr 16 2014

Showers will be possible across the far south and southeast Thursday
night...where lift from the shortwave passing overhead may tap into
the better moisture over MO into central Illinois. Otherwise...light
northeast winds and an influx of dry air around high pressure over
Minnesota will lead to lows from around 30 north to the upper 30s in the
far south under clearing skies. This ridge will provide light winds
and seasonably cool temperatures Friday and Friday night. Saturday
is looking like another breezy and mild day as a strong low level
southerly flow and deep mixing precedes the next storm system moving
into the northern plains. Even modest mixing into the warm advection
regime with 850 mb temperatures approaching 10 degree c would boost
highs well into the 60s to possibly lower 70s. This is considerably
warmer than the previous forecast...and may still need further upward
adjustments based on latest model runs.

Saturday night through Monday...a weakening low is depicted passing
to the north...laying out a slow moving front over the forecast area
that would provide the focus for rain and possible thunderstorms
through Sunday night. By Sunday night...latest operational models
part ways in the handling of shortwaves and how they phase in the
split flow. GFS latest drives the boundary well to the southeast
Sunday night...while the European model (ecmwf) and Gem keep it over Iowa into southern
WI...suggesting at least chances for showers over the region well
into Sunday night. For now...taking a blended approach...will
continue low confidence chance probability of precipitation from Saturday night through
Sunday night into Monday. With sufficient middle level instability and
Gulf moisture availability...will mention a chance of thunderstorms
Saturday night. Temperatures will be greatly dependent on the
frontal location and timing/coverage of precipitation. At this
time...the forecast leans more heavily toward the GFS with highs in
the 60s and lows in the 40s.

Tuesday and real dump of cold air is expected
following the Sunday system and temperatures should be near to
perhaps above normal. Rain chances increase toward Wednesday where
the current model runs have a warm front and surge of Gulf moisture
ahead of what looks to be a much stronger...more significant storm
system showing up for late next week.


Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 300 PM CDT Wednesday Apr 16 2014

VFR conds through this taf cycle. South winds sustained at 20 to
28 knots with gusts to 30 to 38 knots for the remainder of this
afternoon into this evening before diminishing and veering to the
west overnight. West to northwest winds around 10 knots on Thursday


Dvn watches/warnings/advisories...


short term...haase
long term...11