Scientific Forecaster Discussion
fxus63 klsx 072126
Area forecast discussion
National Weather Service Saint Louis MO
326 PM CST Sat Dec 7 2019
Short term... (through late Monday night)
issued at 324 PM CST Sat Dec 7 2019
Under the influence of a retreating high pressure winds have turned
southerly, allowing temperatures to warm today to near normal. This
pattern will persist into tomorrow afternoon, keeping tomorrow's
high temperatures a couple degrees above normal as well. How much
warming occurs depends on whether lingering low stratus in the lower
Mississippi Valley today will expand tonight and build north into
our southern County Warning Area. Have lowered temperatures 2-5 degrees from
previous forecast to account for the forecasted increasing cloud
cover, however if clouds do not build into the area until the
afternoon temperatures will be higher than forecast.
By Sunday afternoon rain is starting to build into the northwest
part of the County Warning Area ahead of the approaching cold front. Chances of rain
continue to increase through the overnight hours. Mid level
disturbances begin to roll through the bi-state region early Monday
ahead of the trough axis and main area of forcing along the front.
The surface cold front moves through the County Warning Area during the day Monday,
pushing the main area of rain ahead of it. 925-850 frontogenetical
forcing and warm air advection are the main drivers of rain, indicating the rain
will be banded rather than a large homogeneous mass. The highest
pops reside in southeast Missouri and southern Illinois where warm air advection is
focused ahead of the front. By late Monday the front will have edged
out of the cwa, leaving cold, dry conditions in it's wake.
Long term...(tuesday through next saturday)
issued at 324 PM CST Sat Dec 7 2019
Behind the cold front a strong Arctic high will build into the
Midwest as anticipated by previous ensemble guidance. The associated
northwest winds will be brisk, advecting cold air into the area and
keeping temperatures about 10-15 degrees below normal Tuesday
through Thursday. Dry conditions are expected until the end of the
work week due to the influence of the strong high over the region.
By Thursday the high has been shunted off to the Ohio River valley
and the southerly flow along the western side of the high will
moderate temperatures to near normal Friday. A chance of
precipitation returns to the forecast at the end of the week into
the weekend, however there is little consensus among the models at
this time. Thus, have low pops for the early next weekend.
Aviation... (for the 18z tafs through 18z Sunday afternoon)
issued at 1110 am CST Sat Dec 7 2019
VFR conditions are forecast to prevail through the end of the taf
period. There is a chance that MVFR stratus will build in near the
Metro terminals tonight, however the majority of guidance is
showing the stratus deck remaining to the east and south of the
Cloud cover will increase tomorrow morning through the
afternoon. Mid level clouds are forecast to build in through the
morning and should have no impact on the terminals. Southerly
winds should start to gust into the upper teens to 20 knots
tomorrow morning and remain through the end of the period.
Specifics for kstl:
VFR conditions should prevail through the end of the taf period.
MVFR stratus is possible near kstl tonight, however the majority
of guidance is showing the stratus deck staying to the east and
south of kstl. Cloud cover will increase through the day tomorrow
as mid level clouds and diurnal cu build in through the day.
Southerly winds will begin to gust into the upper teens to near 20
starting mid morning and continuing to the end of the taf period.