Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 070832

Area Forecast Discussion
National Weather Service Columbia SC
332 AM EST Wed Dec 7 2016

Dry high pressure will briefly build across the forecast area
today. A stronger cold front will cross the region Thursday
bringing the coldest air mass of the season to end the week into
the weekend. Another chance of rain early next week.


Latest analysis shows low pressure lifting away from the region
off the VA Tidewater coast with a cold front well offshore. Water
vapor imagery shows dry air over the region while IR satellite
reveals widespread stratus across most of the region resulting
from low level moisture trapped beneath the inversion. Regional
observations show patchy dense fog mainly near the Savannah River
but the dense fog may expand through the predawn hours and a
dense fog advisory may be needed.

Wedge conditions expected to slowly erode today with gradually
improving visibilities and breaks in the lower clouds although
there does remain some uncertainty due to generally weak low
level flow. This could have an impact on temperature forecast
with cooler temperatures if clouds do not clear out and have
decided to go slightly below MOS guidance with highs ranging from
upper 50s north to lower 60s south.

Clouds will increase again tonight ahead of an approaching cold
front and upper trough, but any precipitation should hold off due
to limited moisture with precipitable water values around 0.6 to
0.7 inches. Overnight lows will be in the 40s.


Upper trough will move across the Ohio Valley Thursday pushing a
cold front through the forecast area. Moisture is limited with
the front with precipitable water values peaking around 0.8-0.9
inches. Low level flow will become west to northwesterly as the
front approaches and that downsloping component will further
inhibit rain chances so will continue to carry slight chance pops
mainly north of Columbia on Thursday. Skies will be mostly cloudy
through the day which will limit temperatures a bit with highs
expected to range from the upper 50s western and northern
Midlands to lower to mid 60s eastern Midlands.

Behind the front Thursday night, a very cold Canadian continental
polar air mass will build into the region with strong cold
advection. Skies expected to clear and the combination of a very
dry air mass and strong radiational cooling will support overnight
lows in the upper 20s to lower 30s. Neutral to slight cold
advection will continue on Friday with northerly low level flow
under mostly clear skies. Highs on Friday will be well below
normal ranging from the lower 40s northern Midlands to upper 40s
in the CSRA.


The extended forecast period will feature cold and dry conditions
early in the period followed by some moderating temperatures and
increasing chances of rain by early next week.

The center of the polar high is expected to be located over the
Central/Southern Appalachians Friday night/Saturday morning. Some
uncertainty as to how ideal the radiational cooling conditions
will be as the high center may remain just to our north. However,
if the high center can get close enough, this air mass is cold and
dry enough to support undercutting guidance min temps for early
Sat morning. Will continue with low temperatures Friday night in
the 20-25 degree range. High pressure at the surface and zonal
westerly 500mb flow on Saturday with mostly clear skies should
allow for slight warming compared to Friday but temperatures will
remain well below normal with highs in the 40s.

The next storm system will develop over the Plains states and
western Ohio Valley region on Sunday as shortwave energy tracks
across the midwest with a surface low developing and lifting
northeastward into the Great Lakes region by Sunday evening. This
will push another cold front towards the region Sunday night into
Monday bringing the next chance for rain. There remain some
differences among the medium range models with the timing of the
front but rain will be possible Sun night into Monday.
Temperatures will moderate Sunday as the surface high shifts
offshore and a southerly flow returns.


Surface high pressure across the area. Shallow low-level moisture
across the region with light surface winds. A moderately strong
low-level jet will weaken during the early morning hours. Patchy
fog developing at 06z. Guidance including HRRR and Rap suggesting
stratus build down/dense fog developing during the overnight into
the early morning. So LIFR/IFR conditions expected with moderately
high confidence. Improving visibility by 15z but stratus/strato-cu
likely to remain through the afternoon as inversion remains strong
and winds light and variable. Conditions expected to only improve
to MVFR in the afternoon.

Restrictions possible tonight with low clouds/fog. A cold front
with little moisture will move through the area Thursday. Breezy
conditions may be associated with the front.




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