Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Huntsville Alabama
245 PM CDT Tuesday Apr 21 2015
the 19z surface analysis indicated that a decent ridge of high
pressure was centered over west central Mississippi. Skies were
mostly sunny across the forecast area with temperatures in the middle to upper
60s. For tonight...skies should begin mostly clear...with an increase
of middle and high clouds expected overnight. Will go with an overall
partly cloudy forecast for the area tonight. Will trend toward the
slightly cooler NAM temperatures for overnight low temperatures.
A cold front is prognosticated by the models to progressively move southeast
from the Midwest into the lower Ohio Valley overnight and into middle
Tennessee by 18z Wednesday. Will continue with chance probability of precipitation for
especially Wednesday afternoon across the forecast area. A short wave
along the frontal boundary is expected to take shape to the west of
the forecast area by 12z Thursday. Will continue with 30-40 percent
probability of precipitation from late Wednesday through Thursday afternoon. The models are
fairly similar in progressively shifting the short wave east of the
forecast area into Georgia by 00z Friday...with a weak area of high
pressure moving across the lower Ohio and Tennessee Valley region.
An area of low pressure is expected to form near the Texas Panhandle
area by Friday on the western end of the old frontal boundary. Low
level moisture is prognosticated by the models to increase with time and
precipitable water values are expected to be above 1.3 inches by Friday afternoon.
Expect that precipitation chances will increase during the afternoon across
northwest Alabama and will spread east-northeast with time into
Friday evening. Will continue with likely pop wording for Friday
night. The models move the surface low northeast into western
Missouri by 12z Saturday and a warm front well to the north of the
forecast area. Most of the precipitation should shift east and northeast of
the forecast area by Saturday afternoon...with warmer and humid
conditions expected. Will lower probability of precipitation for Saturday afternoon and into
Saturday night...as there should be a lack of a triggering mechanism
across the forecast area to the south of the warm front and
southeast of the surface low.
The models eventually shift the surface low southeast through the
Tennessee Valley region by early Sunday. Will lower probability of precipitation overnight
Saturday night and keep conditions dry for Sunday. The next system to
affect the forecast area will progressively move northeast out of the
southwest U.S. In the southern stream into the region by Monday. Have
kept precipitation chances in the chance category for now...but this may
need to be upgraded if model consistency continues. Will maintain
rain showers/thunderstorms and rain chances into Tuesday as the system departs the region. Have
generally moved temperatures slightly upward into the extended forecast
period...but have gone close to model guidance from Monday through
/issued 1154 am CDT Tuesday Apr 21 2015/
for 18z tafs... VFR conditions are forecast during the next 24 hours.
Middle level ceilings will arrive Wednesday morning in advance of a weather
system moving through the Southern Plains.
Preliminary point temps/pops...
Huntsville 48 76 52 66 / 0 30 40 30
Shoals 50 75 51 66 / 0 30 40 30
Vinemont 49 72 52 65 / 0 30 40 30
Fayetteville 47 72 49 63 / 0 30 40 30
Albertville 48 72 52 67 / 0 30 50 40
Fort Payne 43 76 51 65 / 0 30 40 30
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