Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Mobile Alabama
506 am CDT Monday Sep 22 2014

Short term (today through Wednesday night)...the long anticipated
front will be at our northern doorstep as of around 12z and sweeping
through our neck of the Woods this afternoon. The 1000-500 mb half of
the atmosphere will be somewhat conducive to scattered convection
with lifted index -2 to -3...cape near 1800 j/kg...and precipitable
water about 1.5 inches.

Upper flow from the northwest...20 to 40 knots with embedded
perturbations...will continue help push the front over the Gulf. A
strong surface high over the middle Mississippi Valley is moving
southeast behind this front bringing cooler dry air behind it.

High temperatures today should be in the middle 80s in the far north
which will already have experienced frontal passage and upper 80s
closer to the coast. Respective to monthly averages it is about
normal. Lows will be below climatological normal values...middle 50s
inland and upper 50s moving to within 50 or so miles of the coast and
lower 60s south of I-10.

Rain chances will be practically none after the front passes by. The
lifted index will exceed plus 2.5 to 3 degrees c...sufficiently
stable to suppress virtually all convection tonight. Precipitable
water below 0.75 inches. 77/blowing dust

Autumn will start out on a refreshing note for the Tuesday and
Wednesday time frame. Low level northeast flow will be established as
a large surface high centered over the Midwest into the middle Atlantic
on Tuesday shifts east into New England by Wednesday. Precipitable
water values will be very low...averaging 0.50-0.75 inches which is 2
Standard deviations below normal for this time of year. This will
keep rain out of the forecast with highs near normal in the low to
middle 80s. Lows both Tuesday and Wednesday nights will range from the
upper 50s to near 60 along and north of Highway 84....with middle 60s
along the I-10 corridor. 34/jfb

Long term (thursday through sunday)...a Rex block in the middle to
upper levels (weak upper low over the southeast/southern Appalachians
and strong ridging across the western Atlantic into the northeast) is
now forecast to persist through the end of the week. At the
surface...low level flow will remain northeasterly. Precipitable
waters are forecast to remain at an inch or lower across the region
on Thursday...and as a result have removed rain chances for
Thursday/Thursday night. By Friday...the 850-700 mb flow will become
more east to perhaps southeast...tapping into deeper Atlantic
moisture and spreading it into the eastern parts of the forecast
area. The moisture may be sufficient enough to result in an isolated
shower or storm during the day Friday east of I-65...but dry
conditions will likely prevail over most areas. However...we will see
an increase in cloud cover by the end of the week.

While middle level ridging will remain strong over the southwest
Atlantic over the weekend...guidance is coming into better agreement
on a significant trough developing over the Southern Plains into the
western Gulf by Saturday and moving east by Sunday. This results in a
deep southerly fetch of tropical moisture moving north into the
forecast area with precipitable waters climbing to or above 2 inches.
This all translates into increasing rain chances as we go through the
weekend...with the highest rain chances currently centered around
Sunday. It should be noted that the European model (ecmwf) is much deeper and slower
with the eastward progression of this middle level trough and continues
to develop an inverted trough over the central Gulf with a weak surface
low developing along the trough axis and moving north into the north
central Gulf Coast by Sunday afternoon. The strength of the European model (ecmwf)
system would result in the potential for a more organized heavy
rainfall event...something it has been rather persistent in
indicating. Will continue to monitor this potential closely through
the course of the week. Highs will remain near normal through the
extended range. Lows moderate to slightly above seasonal levels
over the weekend due to the increasingly tropical airmass. 34/jfb

&&

Aviation...
12z issuance
VFR conditions will prevail through much of the period until a weak
cold front traverses the region today. As of 12z we expect a broken
o overcast decks around 035 and 080 to be along and 40 miles either
side of a line from Waynesboro Mississippi to near Fort Deposit
Alabama. Southeast movement of the front about 20 to 25 knots would
bring it near the coast along a line from Pascagoula Mississippi to
near Opp Alabama by middle afternoon today. Isolated to scattered
showers and thunderstorms are expected as the front approaches this
afternoon and we are considering this to be included as a 2 to 3
hour prob30 group at the terminals. 77/blowing dust

&&

Marine...a Small Craft Advisory is in effect tonight until Wednesday
night for the Gulf waters. A weak cold front is currently located
over central Alabama as of this morning. A large high over middle
Mississippi Valley will build behind it and elongate over the Ohio
Valley and middle Atlantic by the middle of next week. We expect this
feature to bring an episode of strong east winds offshore increasing
up to 20 knots by tonight becoming east 20 to 25 knots by Tuesday
night and near 25 knots Wednesday through Wednesday evening. The
winds are expected to decrease by the weekend. Increasing significant
waves...highest one third being as high as 10 feet at times offshore
through late this upcoming week. A Small Craft Advisory is in effect
until Wednesday night and may need to be extended. 77/blowing dust

&&

Preliminary point temps/pops...
Mobile 88 60 85 65 84 / 30 05 00 05 10
Pensacola 88 66 85 68 84 / 30 10 00 10 10
Destin 87 70 84 70 84 / 30 20 05 10 10
Evergreen 87 55 84 60 84 / 30 05 00 00 10
Waynesboro 86 53 85 59 85 / 30 05 00 00 05
Camden 85 54 83 59 83 / 30 05 00 00 05
Crestview 88 59 85 62 84 / 30 10 05 05 10

&&

Mob watches/warnings/advisories...
Alabama...none.
Florida...none.
MS...none.
GM...Small Craft Advisory from 1 am Tuesday to 7 PM Wednesday for the
following zones: coastal waters from Destin to Pensacola Florida
out 20 nm...coastal waters from Pensacola Florida to Pascagoula
MS out 20 nm...waters from Destin to Pensacola Florida from 20
to 60 nm...waters from Pensacola Florida to Pascagoula MS from
20 to 60 nm...

&&

$$

National Weather Service Glossary of Abbreviations